the number of new cases of lung cancer in the eu will increase by 27% between 2008 and 2025 , in part due to population ageing , and in part due to long - term trends in tobacco use . surgery remains the mainstay of treatment , with curative intent for non - small - cell lung cancer ( nsclc ) patients who are medically fit , with lobectomy as the treatment of first choice . length of stay ( los ) in hospital after surgery impacts on cost and hospital performance [ 35 ] . there is little definitive information on los following lung cancer resection ; yet , the rate of lung cancer resection ( as a proportion of nsclc cases ) is increasing in several european countries [ 68 ] . internationally , the few available studies suggest that there is much variation in the reported median los after nsclc resection [ 5 , 912 ] . postoperative complications are common after lung resection and can result in prolonged hospitalization and early readmission [ 9 , 13 ] . we conducted a population - based analysis of time trends in los and predictors of prolonged los following resection for nsclc in ireland . we further investigated the factors predicting emergency readmission within 28 days of discharge after the index procedure ( ip ) . the primary data sources for this study were the national cancer registry ( ncr ) and the hospital in - patient enquiry ( hipe ) database in ireland [ 14 , 15 ] . hipe is a computer - based information system that records data on discharges from all acute public hospitals and a few private hospitals . lung cancer patients ( icd - o2 : c34 ) newly diagnosed between 2002 and 2008 were identified from the ncr . individuals who had another primary cancer prior to the lung cancer ( other than non - melanoma skin ) were excluded . the dataset was then limited to those who had lung cancer resection according to ncr records ( icd9-cm codes 32.2x , 32.3 , 32.4 , 32.5 , 32.6 , 32.9 , 34.4x ) . using probabilistic matching techniques , these patients were linked to hipe episodes ( fig . 1 ) . coverage of private hospitals by hipe is very incomplete and we limited our analysis to patients treated in public hospitals . cases with tumour morphology codes of m8039 - 8046 ( small cell carcinoma ) were then excluded . the date of surgical resection ( ip ) recorded by the ncr was matched to the corresponding hipe episode . the final analysis dataset included 1284 patients with nsclc who underwent a resection ( fig . los was calculated as the number of days between the admission date for the ip and the discharge date , or death ( if the patient died in hospital ) ( i.e. this was the total of preoperative and postoperative los ) . duration of discharge was calculated as the time from discharge following the ip to the first emergency readmission to a public hospital ( if any ) . emergency when the patient required immediate care and treatment as a result of a severe , life - threatening or potentially disabling condition . in the uk , 28-day readmission rate is a key hospital performance indicator [ http://www.nchod.nhs.uk ] ; therefore , we based our analysis on emergency readmissions where the duration of discharge was < 29 days . a range of patient , tumour and health - service - related variables were abstracted from the ncr and hipe databases and investigated for associations with los and emergency readmission . details on age at diagnosis , gender and marital status were available from the ncr . socioeconomic status was measured in terms of the level of deprivation of each patient 's local area of residence at diagnosis using a score created from 2002 census variables . the score was derived for each of the 3409 electoral districts in ireland ; the districts were categorized into five levels of deprivation . in our dataset , the number of patients resident within a quintile 5 district (  most deprived ) was double that of any other quintile in our study . we therefore pooled quintiles 14 (  less deprived ) for comparison with quintile 5 ; this is also consistent with what was done in a large us study of los and lung resections among medicare recipients . each case was classified according to smoking status at diagnosis , which was derived by the ncr from hospital charts , and defined as : ( i )  never smoked , ( ii )  ex - smoker did not smoke more than once a month for the past year and ( iii ) cases were classified by summary stage of disease . where information on distant metastasis ( mx ) was not recorded , these cases were treated as m0 . a comorbidity score for each patient , based on the charlson index , was derived from all diagnoses recorded in hipe for the ip episode ; the lung cancer diagnosis was disregarded in this calculation . resection procedures were categorized as : lobectomy , pneumonectomy , segmental / wedge resections and  other procedures. patients were classified as  private or public ( this refers to whether the patient saw the surgeon as a private or public patient ) . the patient 's destination at discharge after ip was classified as : home , other healthcare facility ( i.e. another acute / step - down hospital , nursing home or hospice ) , or death in hospital after ip . resections for nsclc were performed in six public hospitals during 20028 . lower volume depending on whether they were operated on in a hospital above , or below , the median resection count / hospital / year respectively ( 40/hospital / year ) . median los , and ranges ( upper and lower decile of los ) were computed at each level of the sociodemographic , clinical and health - service - related variables . wallis equality - of - populations rank test and cuzick 's test for trend . in the absence of any published definition of prolonged los in europe , the cut - point defining the upper quartile of patients ( > 20 days ) was selected as a practical threshold for prolonged los ; this also happened to be 1 week longer than the median los ( 13 days ) . as the outcome was common , instead of using logistic regression to estimate odds ratios , we modelled prolonged los using poisson regression with a log link and robust variance to estimate risk ratios and associated 95% confidence intervals . three types of variables were considered for inclusion in the model : sociodemographic ( age , gender , marital status , deprivation , smoking status and public / private status ) ; clinical ( ip type , stage and comorbidity ) and health - service related ( hospital volume , destination at discharge ) . a backward stepwise variable selection approach for modelling was used , removing variables in order of least significance until all retained variables achieved p < 0.1 in likelihood ratio tests ( lrts ) . as a sensitivity analysis , we also modelled los as a continuous variable using linear regression after a log transformation to normalize the distribution of los . poisson regression with a log link and robust variance   was also used to estimate risk ratios for factors predicting emergency readmissions within 28 days after discharge . patients who had not died in hospital were classified as : ( a ) emergency readmission within 28 days of discharge , or ( b ) not readmitted as an emergency within 28 days of discharge . the primary reason for the emergency readmission was derived from the hipe diagnostic codes for that admission . median los , and ranges ( upper and lower decile of los ) were computed at each level of the sociodemographic , clinical and health - service - related variables . wallis equality - of - populations rank test and cuzick 's test for trend . in the absence of any published definition of prolonged los in europe , the cut - point defining the upper quartile of patients ( > 20 days ) was selected as a practical threshold for prolonged los ; this also happened to be 1 week longer than the median los ( 13 days ) . as the outcome was common , instead of using logistic regression to estimate odds ratios , we modelled prolonged los using poisson regression with a log link and robust variance to estimate risk ratios and associated 95% confidence intervals . three types of variables were considered for inclusion in the model : sociodemographic ( age , gender , marital status , deprivation , smoking status and public / private status ) ; clinical ( ip type , stage and comorbidity ) and health - service related ( hospital volume , destination at discharge ) . a backward stepwise variable selection approach for modelling was used , removing variables in order of least significance until all retained variables achieved p < 0.1 in likelihood ratio tests ( lrts ) . as a sensitivity analysis , we also modelled los as a continuous variable using linear regression after a log transformation to normalize the distribution of los . poisson regression with a log link and robust variance   was also used to estimate risk ratios for factors predicting emergency readmissions within 28 days after discharge . patients who had not died in hospital were classified as : ( a ) emergency readmission within 28 days of discharge , or ( b ) not readmitted as an emergency within 28 days of discharge . the primary reason for the emergency readmission was derived from the hipe diagnostic codes for that admission . of 12 139 incident cases of invasive lung cancer diagnosed in ireland between 2002 and 2008 , 1284 had nsclc and underwent lung resection in public hospitals ( fig . 1 ) . of these , 72% underwent lobectomy , 17% underwent pneumonectomy , 4% had segmental / wedge resection and 7% had another excision procedure . there was a significant increase in lung cancer resections performed per annum ( expressed as a proportion of nsclc cases ) between 2002 and 2008 ( 142/1415 ( 10% ) in 2002 , rising to 228/1613 ( 14% ) in 2008 ; p - trend = 0.000012 ) . the median total los was 13 days ( inter - decile range ( idr ) : 735 days , mean = 18 days and range : 1343 days ) . the median los decreased significantly from 15 days in 2002 to 12 days in 2008 ( p - trend = 0.037 ) ( table 1 ) . the median preoperative los for the period 20028 was 1 day ( idr : 06 days ) . this decreased significantly over time , from 3 days [ idr : 116 ] in 2002 , to 1 day [ idr : 03 ] in 2008 ( p - trend = 0.0000000000021 ) . table 1:patients with nsclc undergoing resection , 20028 : numbers ( n ) , percentages ( % ) and median and idr los and p - valuesvariablescategoriesn%median losidrp - valuetotal1284100%13[735]age at diagnosis<55 year20416%10[525]0.0000000175564 year42333%12[730]6574 year47937%13[737]>75 year17814%15[750]genderfemale54142%12[732]0.22male74358%13[736]marital statusmarried81063%12[731]0.019other47437%13[740]deprivation1 least23018%12[635]0.016216613%12[527]314411%12.5[730]418715%12[628]5 most48037%13[739]unknown776%13[731]smoking statusnever smoker12410%12.5[634]0.67ex - smoker43434%12[733]current smoker60447%13[738]unknown12210%10[223]health insurancepublic88469%13[736]0.017private ( held private health insurance)40031%12[631]stagestage i / ii85467%13[736]0.023stage iii+30924%13[733]unstaged1219%10[422]comorbidity093173%12[632]0.000000026126421%13[836]2 + 897%18[859]procedurelobectomy90971%12[735]0.14pneumonectomy23418%13[733]segmental / wedge excision494%13[642]other excision927%15[437]discharge statusto home97076%12[729]0.00000059to care ( other acute hospital / nursing home / hospice)23018%12[245]died in hospital post - ip847%21.5[1091]hospital volumehigher volume : 40/year66151%12[631]0.000076lower volume : < 40/year62349%13[737]year of incidence200214211%15[836]0.037200317414%12[734]200415312%13[832]200518715%12[434]200617614%13[729]200722417%13[733]200822818%12[640]p - value : kruskal  wallis test for binary and categorical variables and test for trend with ordinal categorical variables.small area ( electoral district ) based quintile of deprivation.patient had private health insurance or settled own account (  private ) , or did not have health insurance (  public ) at discharge.the patients were classified as  high volume or low volume depending on whether they were operated in a hospital above or below the median resection count / hospital / year respectively ( 40/hospital / year).idr : inter - decile range ( 10th90th centile ) . patients with nsclc undergoing resection , 20028 : numbers ( n ) , percentages ( % ) and median and idr los and p - values p - value : kruskal  wallis test for binary and categorical variables and test for trend with ordinal categorical variables . patient had private health insurance or settled own account (  private ) , or did not have health insurance (  public ) at discharge . high volume or  low volume depending on whether they were operated in a hospital above or below the median resection count / hospital / year respectively ( 40/hospital / year ) . the characteristics of the 1284 cases , together with median and idr los , are shown in table 1 . table 2 presents crude and adjusted risk ratios ( rr ) for factors that were significantly associated with prolonged los in multivariate analyses ( greater than the upper quartile of los , i.e. > 20 days ) . in the adjusted analysis , the risk of prolonged los was significantly higher in patients who were older than 75 years ; lived in the most deprived areas ; had two or more comorbid conditions ; and had undergone surgery in a lower - volume hospital . patients who died in hospital subsequent to the ip were also significantly more likely to have prolonged los . although the percentage of patients who had prolonged los varied slightly according to the procedure received ( lobectomy 25% , pneumonectomy 23% , segmental 31% and other excision 31% ) , this was not statistically significant in adjusted analysis . similarly , stage of disease was not significantly associated with prolonged los after adjusting for other variables ( stage i / ii 25% , stage iii+ 25% and unstaged 16% ) . in the sensitivity analysis , using linear regression , the same variables predicted los as predicted prolonged los . table 2:factors significantly associated with prolonged los in patients having resection for nsclc , 20028 : number ( n ) of total ( n ) ( % ) who had prolonged los ( > 20 days ) , univariate and adjusted rr , with 95% ci and lrtsprolonged los ( > 20 days)univariateadjustedlrtnn%rr95% cirr95% cip - valuetotal312128424%age  < 55 year3720418%110.064  5564 year8542320%1.11[0.78 , 1.57]1.03[0.73 , 1.45 ]  6574 year12847927%1.47[1.06 , 2.04]1.32[0.95 , 1.82 ]  > 75 year6217835%1.92[1.35 , 2.74]1.55[1.08 , 2.23]sex  female13254124%1  male18074324%0.99[0.82 , 1.21]deprivation  less deprived ( q14)15872722%110.060  most deprived ( q5)13848029%1.32[1.09 , 1.61]1.30[1.07 , 1.58 ]  unknown167721%0.96[0.61 , 1.51]1.03[0.66 , 1.62]comorbidity  none20693122%110.073  17026427%1.20[0.95 , 1.51]1.11[0.88 , 1.40 ]  2 + 368940%1.83[1.38 , 2.42]1.60[1.20 , 2.13]hospital volume higher : 40/year14166121%110.086  lower : < 40/year17162327%1.29[1.03 , 1.61]1.24[0.99 , 1.56]discharge status  alive at discharge266120022%110.000074  died in hospital post ip468455%2.47[1.98 , 3.08]2.03[1.60 , 2.57]mutually adjusted for age , deprivation , comorbidity , hospital volume and discharge status ( and year of incidence , not shown).rr : risk ratio ; lrt : likelihood ratio test for exclusion of that variable from multivariable model . factors significantly associated with prolonged los in patients having resection for nsclc , 20028 : number ( n ) of total ( n ) ( % ) who had prolonged los ( > 20 days ) , univariate and adjusted rr , with 95% ci and lrts mutually adjusted for age , deprivation , comorbidity , hospital volume and discharge status ( and year of incidence , not shown ) . rr : risk ratio ; lrt : likelihood ratio test for exclusion of that variable from multivariable model . of 1200 patients who were discharged alive after surgery ( none of whom died within 28 days of discharge ) , 119 ( 10% ) table 3 presents crude and adjusted risk ratios for factors significantly associated with risk of emergency readmission . in the adjusted analysis , risk of readmission was increased in patients from the most deprived areas , with two or more comorbid conditions , and with stage iii+ disease ( table 3 ) . patients > 75 years ( 14% of whom were readmitted , compared with 7 , 10 and 9% in the < 55 year , 5564 year and 6574 year age groups , respectively ) , and those who underwent segmental procedures ( 17% readmitted , compared with 9% for lobectomy , 12% for pneumonectomy and 9% for other procedures ) were also more prone to emergency readmission in univariate analyses ; however , age and procedure type were not significantly associated with readmission after adjustment for the factors in the model . the main reasons for emergency readmission were : pulmonary complications ( 29% ) , cardiovascular / vascular events ( 21% ) and infections ( 20% ) ( table 4 ) . table 3:factors significantly associated with emergency readmission in patients having resection for nsclc , 20028 : number ( n ) of total ( n ) ( % ) who were readmitted within 28 days ) , univariate and adjusted rr with 95% ci and lrtreadmitted within 28 dayscrudeadjustedlrtnn%rr[95% ci]rr[95% ci]p - valuetotal119120010%age  < 55 year152017%1  5564 year4240610%1.39[0.79 , 2.44 ]  6574 year414419%1.25[0.71 , 2.20 ]  > 75 year2115214%1.85[0.99 , 3.47]sex  female5052110%1  male6967910%1.06[0.75 , 1.50]deprivation  less deprived ( q14)576858%110.0095  most deprived ( q5)5944113%1.61[1.14 , 2.27]1.56[1.11 , 2.20 ]  unknown3744%0.49[0.16 , 1.52]0.48[0.16 , 1.45]comorbidity  none748798%110.011  13024412%1.46[0.98 , 2.18]1.43[0.96 , 2.12 ]  2 + 157719%2.31[1.40 , 3.83]2.38[1.43 , 3.96]stage  stage i / ii728019%110.039  stage iii+3928114%1.54[1.07 , 2.23]1.62[1.13 , 2.34 ]  unstaged81187%0.75[0.37 , 1.53]0.83[0.41 , 1.69]mutually adjusted for deprivation , comorbidity and stage.rr : risk ratio ; lrt : p - value of likelihood ratio test for exclusion of that variable in multivariable model . table 4:primary reason for first emergency readmission within 28 days of ipreadmission causedescriptionn ( % ) subtotal number ( % ) pulmonary complicationatelectasis11 ( 9%)pneumonia8 ( 7%)pulmonary air leak6 ( 5%)pleural effusion7 ( 6%)empyema2 ( 2%)34 ( 29%)cardiovascular / vasculardysrhythmia18 ( 15%)myocardial infarction4 ( 3%)cerebrovascular event3 ( 3%)25 ( 21%)infectionwound infection6 ( 5%)fever14 ( 12%)urinary tract infection3 ( 3%)23 ( 20%)othersrenal insufficiency2 ( 2%)others35 ( 29%)37 ( 31%)total119 ( 100% ) factors significantly associated with emergency readmission in patients having resection for nsclc , 20028 : number ( n ) of total ( n ) ( % ) who were readmitted within 28 days ) , univariate and adjusted rr with 95% ci and lrt mutually adjusted for deprivation , comorbidity and stage . rr : risk ratio ; lrt : p - value of likelihood ratio test for exclusion of that variable in multivariable model . our dataset of > 1200 lung cancer resections conducted in patients incident during 20028 is relatively large by european standards and provides for the first time , as far as we are aware , detailed information on factors predicting prolonged los , and emergency readmission from a european population - based series . to our knowledge , apart from one study in japan , it is the only population - based study to investigate los in patients of all ages ; the other large population - based studies of los  from the usa  were restricted to patients aged 65 and older [ 4 , 5 ] . only 24 ( < 2% ) cases recorded by the ncr as having a resection in a public hospital had no corresponding hipe record . failure to find a match can occur for several reasons including : typographical errors in fields used for matching , missing data on either system or no mention of cancer on the hipe record , in which case the record would not be made available to ncr . the small numbers of missing episodes were distributed across hospitals and years . compared with other cancers , surgery with curative intent for nsclc is relatively uncommon , typically being undertaken in a minority of patients ( e.g. 1011% in england   and 1619% in norway ) . we did not have access to data on lung function and derived a comorbidity score instead to provide some measure of likely health status . in our study , the median los ( 13 days ) was considerably greater than that observed in canada ( 6 days , based on 360 patients )   and spain ( 7 days , n = 727 ) . however , these data derived from case series from single centres may not be directly comparable to other hospitals or countries . several large population - based studies have presented median los after lung cancer resection : us thoracic surgery database audit ( 6 days ) , us medicare database audit ( 10 days ) , us seer subset of medicare recipients ( 6 days ) , japan ( national audit of lobectomy , mean 13.7 days ) , and a uk multicentre cohort study ( 9 days for pneumonectomy , n = 312 , 2005 ) . there is no single obvious reason why ireland should have such prolonged los for lung resection compared with other countries . in published papers , it is not always entirely clear how los has been computed and whether the authors included ( as we have done ) preoperative los . when we discounted preoperative los , postoperative los in ireland ( median = 12 days , data not shown ) was still much greater than that of any other country with published information . los in ireland following colorectal cancer surgery   was also relatively high compared with international norms ; this suggests that system - level or hospital - level practices account for the findings to some degree . the largest studies on los were undertaken within the us healthcare system where every cost item ( including los ) is rigorously controlled by health insurers , which probably explains why the los in these studies is markedly lower than that of ireland . the ( postoperative mean ) estimate of los in ireland was not much greater than that of japan . note that unlike in the usa , immediate postoperative care and subsequent nursing care tend to be combined within the same hospital episode , which is why los is much greater in japan than in the usa . excess days los in irish hospitals may be devoted to subsequent nursing care rather than immediate postoperative care , as happens in japan , but we are unable to determine this from the data available . the dutch national medical registration system has proposed that all hospitals should aspire to achieve an average los for each specialty , equal to that of a benchmark model hospital for that specialty . shorter hospital stay as a result of improved discharge efficiency could reduce cost per patient and increase patient throughput . the observed associations between older age and more comorbidities and increased risk of prolonged los in our study are probably unsurprising . however , they do suggest that los following lung resection is not easily reduced , short of restricting surgery to the youngest and healthiest patients . our finding of reduced risk of prolonged los in higher - volume hospitals is consistent with a large national audit in japan , but not with a large national audit of the us medicare population ( > 65 years ) in the usa . apart from the much smaller number of hospitals performing lung cancer surgery in ireland , the number of nsclc resections / hospital carried out within irish hospitals was within the same order of magnitude as that of the usa and japan . although the  excess los for patients in lower - volume hospitals in our study was modest ( only 2 days on average ) , this has the potential to impact significantly on hospital budgets in ireland ( and elsewhere ) ; this should be a particular concern for service providers in light of the increasing incidence of lung cancer projected in many populations and the increasing resort to surgical interventions [ 68 ] . one potential implication of our findings is that further centralization of surgical expertise towards higher - volume hospitals in a small county like ireland could provide a way to constrain los and achieve better economy of scale . we also observed for the first time as far as we are aware that patients resident in the most deprived areas were more likely to have a prolonged los . another study reported that patients with longer los following lung cancer surgery have higher mortality rates 2.5 years post - surgery . this suggests that the association between deprivation and los explains , at least in part , the poorer survival found in socioeconomically disadvantaged lung cancer patients . in terms of potential reasons why more deprived patients might have longer los , it is possible that they are not as prepared for discharge as less deprived patients , for reasons other than clinical factors . for example , in some instances , los could simply depend on access to transport on the proposed day of discharge ( e.g. money for a taxi or availability of a car ) ; such access may be more limited in patients resident in the most deprived areas . also , some characteristics of the most deprived patients were different from other patients . for example , those resident in the most deprived areas were less likely to be married than those resident in other areas ( 41 vs 35% ) . clinicians may be less likely to discharge a patient quickly if they lack a spouse who can provide support and care at home . fewer patients in the most deprived areas were treated privately by the managing consultant ( 22 vs 36% ) , which effectively means that they did not have private health insurance . we have shown , for colorectal cancer , that private patients have shorter los post - surgery , most likely due to pressure from the insurer ( or the patient ) to constrain costs . finally , current smoking was more common among patients resident in the most deprived areas ( 51 vs 45% ) . smokers often have significant co - existing conditions ( which may not have been fully captured by our measure of comorbidity ) and may have poorer general health status , or be in poorer physical condition , thus resulting in longer los . moreover , it is possible that they have poorer lung function , which has been previously reported to be associated with los [ 3 , 10 ] . the main reasons for emergency readmission within 28 days of discharge  pulmonary complications , cardio / cerebrovascular events and infection  were similar to those described in an audit of a us specialist centre . in common with research in the usa , we found that multiple comorbidities and advanced stage predisposed to readmission , and these associations are unsurprising . to our knowledge , the differentials between the  most and  least deprived for various characteristics were detailed above . smoking , which was more common in the deprived category , may have been a factor driving readmissions , as was lack of social support in the unmarried . it is also possible that patients in the most deprived areas were inherently more prone to adverse events due to greater comorbidity , and perhaps were slower to recognize and act upon the development of an adverse event before it became serious enough for emergency readmission , but we are not aware of any data to support this hypothesis . similar to the seer subset study then , any efforts to reduce los in ireland ( or elsewhere ) may not necessarily result in increased readmissions . our dataset of > 1200 lung cancer resections conducted in patients incident during 20028 is relatively large by european standards and provides for the first time , as far as we are aware , detailed information on factors predicting prolonged los , and emergency readmission from a european population - based series . to our knowledge , apart from one study in japan , it is the only population - based study to investigate los in patients of all ages ; the other large population - based studies of los  from the usa  were restricted to patients aged 65 and older [ 4 , 5 ] . only 24 ( < 2% ) cases recorded by the ncr as having a resection in a public hospital had no corresponding hipe record . failure to find a match can occur for several reasons including : typographical errors in fields used for matching , missing data on either system or no mention of cancer on the hipe record , in which case the record would not be made available to ncr . the small numbers of missing episodes were distributed across hospitals and years . compared with other cancers , surgery with curative intent for nsclc is relatively uncommon , typically being undertaken in a minority of patients ( e.g. 1011% in england   and 1619% in norway ) . we did not have access to data on lung function and derived a comorbidity score instead to provide some measure of likely health status . in our study , the median los ( 13 days ) was considerably greater than that observed in canada ( 6 days , based on 360 patients )   and spain ( 7 days , n = 727 ) . however , these data derived from case series from single centres may not be directly comparable to other hospitals or countries . several large population - based studies have presented median los after lung cancer resection : us thoracic surgery database audit ( 6 days ) , us medicare database audit ( 10 days ) , us seer subset of medicare recipients ( 6 days ) , japan ( national audit of lobectomy , mean 13.7 days ) , and a uk multicentre cohort study ( 9 days for pneumonectomy , n = 312 , 2005 ) . there is no single obvious reason why ireland should have such prolonged los for lung resection compared with other countries . in published papers , it is not always entirely clear how los has been computed and whether the authors included ( as we have done ) preoperative los . when we discounted preoperative los , postoperative los in ireland ( median = 12 days , data not shown ) was still much greater than that of any other country with published information . los in ireland following colorectal cancer surgery   was also relatively high compared with international norms ; this suggests that system - level or hospital - level practices account for the findings to some degree . the largest studies on los were undertaken within the us healthcare system where every cost item ( including los ) is rigorously controlled by health insurers , which probably explains why the los in these studies is markedly lower than that of ireland . the ( postoperative mean ) estimate of los in ireland was not much greater than that of japan . note that unlike in the usa , immediate postoperative care and subsequent nursing care tend to be combined within the same hospital episode , which is why los is much greater in japan than in the usa . excess days los in irish hospitals may be devoted to subsequent nursing care rather than immediate postoperative care , as happens in japan , but we are unable to determine this from the data available . the dutch national medical registration system has proposed that all hospitals should aspire to achieve an average los for each specialty , equal to that of a benchmark model hospital for that specialty . shorter hospital stay as a result of improved discharge efficiency could reduce cost per patient and increase patient throughput . the observed associations between older age and more comorbidities and increased risk of prolonged los in our study are probably unsurprising . however , they do suggest that los following lung resection is not easily reduced , short of restricting surgery to the youngest and healthiest patients . our finding of reduced risk of prolonged los in higher - volume hospitals is consistent with a large national audit in japan , but not with a large national audit of the us medicare population ( > 65 years ) in the usa . apart from the much smaller number of hospitals performing lung cancer surgery in ireland , the number of nsclc resections / hospital carried out within irish hospitals was within the same order of magnitude as that of the usa and japan . although the  excess los for patients in lower - volume hospitals in our study was modest ( only 2 days on average ) , this has the potential to impact significantly on hospital budgets in ireland ( and elsewhere ) ; this should be a particular concern for service providers in light of the increasing incidence of lung cancer projected in many populations and the increasing resort to surgical interventions [ 68 ] . one potential implication of our findings is that further centralization of surgical expertise towards higher - volume hospitals in a small county like ireland could provide a way to constrain los and achieve better economy of scale . we also observed for the first time as far as we are aware that patients resident in the most deprived areas were more likely to have a prolonged los . another study reported that patients with longer los following lung cancer surgery have higher mortality rates 2.5 years post - surgery . this suggests that the association between deprivation and los explains , at least in part , the poorer survival found in socioeconomically disadvantaged lung cancer patients . in terms of potential reasons why more deprived patients might have longer los , it is possible that they are not as prepared for discharge as less deprived patients , for reasons other than clinical factors . for example , in some instances , los could simply depend on access to transport on the proposed day of discharge ( e.g. money for a taxi or availability of a car ) ; such access may be more limited in patients resident in the most deprived areas . also , some characteristics of the most deprived patients were different from other patients . for example , those resident in the most deprived areas were less likely to be married than those resident in other areas ( 41 vs 35% ) . clinicians may be less likely to discharge a patient quickly if they lack a spouse who can provide support and care at home . fewer patients in the most deprived areas were treated privately by the managing consultant ( 22 vs 36% ) , which effectively means that they did not have private health insurance . we have shown , for colorectal cancer , that private patients have shorter los post - surgery , most likely due to pressure from the insurer ( or the patient ) to constrain costs . finally , current smoking was more common among patients resident in the most deprived areas ( 51 vs 45% ) . smokers often have significant co - existing conditions ( which may not have been fully captured by our measure of comorbidity ) and may have poorer general health status , or be in poorer physical condition , thus resulting in longer los . moreover , it is possible that they have poorer lung function , which has been previously reported to be associated with los [ 3 , 10 ] . the main reasons for emergency readmission within 28 days of discharge  pulmonary complications , cardio / cerebrovascular events and infection  were similar to those described in an audit of a us specialist centre . in common with research in the usa , we found that multiple comorbidities and advanced stage predisposed to readmission , and these associations are unsurprising . to our knowledge , the differentials between the  most and  least deprived for various characteristics were detailed above . smoking , which was more common in the deprived category , may have been a factor driving readmissions , as was lack of social support in the unmarried . it is also possible that patients in the most deprived areas were inherently more prone to adverse events due to greater comorbidity , and perhaps were slower to recognize and act upon the development of an adverse event before it became serious enough for emergency readmission , but we are not aware of any data to support this hypothesis . similar to the seer subset study , prolonged los did not predict emergency readmission . by implication then , any efforts to reduce los in ireland ( or elsewhere ) may not necessarily result in increased readmissions . half of the patients undergoing resection for nsclc stay in hospital for > 13 days . deprivation , greater age , comorbidity and treatment at a lower - volume hospital were identified as risk factors for prolonged los . deprivation also predicted emergency readmission with 28 days , as did comorbidity and more advanced stage . since socioeconomic disadvantage is related to poorer survival from lung cancer , in the interests of equity , the reasons for the observed associations between deprivation and los and readmission require elucidation .
objectiveswe conducted a population - based analysis of time trends in length of stay ( los ) , predictors of prolonged los and emergency readmission following resection for non - small - cell lung cancer ( nsclc).methodsincident lung cancers ( icdo2:c34 ) , diagnosed between 2002 and 2008 , were identified from the national cancer registry ( ncr ) of ireland , and linked to hospital in - patient episodes ( hipe ) . for those with nsclc who underwent lung resection , the associated hospital episode was identified . 
 factors predicting longer los ( upper quartile , > 20 days ) , and emergency readmission within 28 days of the index procedure ( ip ) were investigated using poisson regression.resultsa total of 1284 patients underwent resection . 
 eighty - four ( 7% ) subsequently died in hospital and 1200 ( 93% ) were discharged . 
 hundred and nineteen of 1200 ( 10% ) were readmitted as an emergency within 28 days of discharge . 
 median los after the ip was 13 days ( inter - decile range : 735 ) . 
 risk of prolonged los was significantly greater in patients > 75 years , resident in an area of highest deprivation , with 2 + comorbidities , who had undergone surgery in a lower - volume hospital , and died in hospital subsequent to the ip . 
 emergency readmission was significantly more likely in patients who were resident in an area of highest deprivation , with 2 + comorbidities , and had stage iii disease or worse . 
 the main reasons for emergency readmission were : pulmonary complications ( 29% ) , cardio / cerebrovascular events ( 21% ) or infection ( 20%).conclusionshalf of the patients had a los in excess of 13 days , which was longer than any other country with published data . patient and health - service factors were associated with prolonged los , while patient and tumour characteristics were associated with risk of emergency readmission . 
 deprivation was a conspicuous determinant of both los and readmission .