otitis media is defined as infection in the middle ear . acute otitis media ( aom ) is one of the most common infections in children under 15 years of age.1 aom can cause serious symptoms such as fever , otalgia , and otorrhea , all of which may be associated with the use of considerable medical resources . otitis media with effusion ( ome ) resulting from aom can impair hearing , affecting children 's school performance and speech development . in general , aom can disrupt a child 's daily activities and have a profound negative impact on the quality of life.24   aom is a disease that is prevalent in the pediatric population . prevention and management of aom are important from a public health point of view . to improve clinical care and properly allocate medical resources , although the recent us national health interview survey described declining rates of aom occurrence , antibiotic prescriptions , office visits for aom , and middle ear surgery since the licensure and routine use of the pneumococcal conjugate vaccine in infants , the panel report also recommended more research on otitis media to further reduce aom incidence.5   although mounting data concerning the prevalence and incidence of aom are available in epidemiological studies , the comparison and extrapolation of epidemiological data from these studies is difficult , if not impossible , mainly due to dissimilarities in study design , sampling methodology , and diagnostic consistency.24 although the threat that aom poses to children has been well recognized , limited information is available concerning the nationwide incidence and recurrence of aom in taiwan 's pediatric population . using the 2006 - 2007 national health insurance ( nhi ) claims database , this study sought to investigate the epidemiological characteristics of pediatric aom in taiwan . we also aimed to identify the pediatric aom patients who are at a greater risk of recurrence . a universal nhi program , which is administered by the bureau of nhi ( bnhi ) under the jurisdiction of the department of health , was implemented in taiwan in march 1995 . approximately 96% of the taiwanese population enrolled in the nhi program,6 and the state - run bnhi had contracted with 97% of hospitals and 90% of clinics all over the country by the end of 1996.7 the bnhi accumulates all administrative and claims data , and the national health research institute ( nhri ) cooperates with the bnhi to maintain an nhi research database . the nhri protects the privacy and confidentiality of all beneficiaries and transfers the health insurance data to health researchers after ethical approval has been obtained . to ensure the accuracy of the claim files , the bnhi performs expert reviews on a random sample of every 50 - 100 ambulatory and inpatient claims in each hospital and clinic quarterly , and false reports of diagnosis receive a severe penalty from the bnhi.8 in this study , we used data from the ambulatory care claims ( 2006 - 2007 ) and inpatient claims ( 2006 - 2007 ) and updated registry for beneficiaries ( 2007 ) . all nhi datasets can be linked with each individual 's personal identification number ( pin ) . this study aimed to estimate the recurrent rate of aom in taiwan 's child population and to identify the groups at high risk of recurrence . to meet these goals , we adopted a cohort study design . the study cohort consisted of all 283,084 children who had ambulatory care visits or were hospitalized with a primary or secondary diagnosis of aom ( international classification code 9 version clinical modification ( icd-9-cm ) : 381.xx or 382.xx ) between january 14 and december 31 , 2006 . the dates of their first - time ambulatory care visit or hospitalization in 2006 were set as the baseline ( initial ) aom attack . baseline information was retrieved from claims data , including the patient 's date of birth , gender , place of care ( clinics , district or regional hospitals , medical centers ) , and the specialty of the attending physician . the age of the study subjects was calculated as the difference between the date of the baseline attack and the date of birth . with their unique pins , the individuals who comprised the study cohort could be linked to the 2006 - 2007 ambulatory care and inpatient claims to identify the possible recurrence of aom within 12 months following the baseline attack . only subsequent ambulatory care visits ( or hospitalizations ) with a primary or secondary diagnosis of aom and with a date of ambulatory care visit ( or hospitalization ) at least 15 days apart from the previous aom ambulatory care visit ( or hospitalization ) were considered new episodes ( i.e. , recurrence ) . using the 2007 updated registry for beneficiaries , we were able to calculate the person - years ( pys ) for which each study subject had been observed from the baseline attack either to the date of termination of the nhi policy ( primarily due to death ) or to the 365th day . we then calculated the cumulative incidence rate ( cir ) and incidence density rate ( idr ) per 100 pys for aom within one year of follow - up , according to various subjects ' characteristics . the idr was calculated as the ratio of the total number of aom recurrences ( i.e. , frequency ) to the total number of pys observed . last , we used a multivariate logistic regression model to assess the independent effects of age , gender , place of treatment , and physician specialty on the risk of 1-year aom recurrence . all statistical analyses were performed with sas ( version 9.1 ; sas institute , cary , nc ) . a universal nhi program , which is administered by the bureau of nhi ( bnhi ) under the jurisdiction of the department of health , was implemented in taiwan in march 1995 . approximately 96% of the taiwanese population enrolled in the nhi program,6 and the state - run bnhi had contracted with 97% of hospitals and 90% of clinics all over the country by the end of 1996.7 the bnhi accumulates all administrative and claims data , and the national health research institute ( nhri ) cooperates with the bnhi to maintain an nhi research database . the nhri protects the privacy and confidentiality of all beneficiaries and transfers the health insurance data to health researchers after ethical approval has been obtained . to ensure the accuracy of the claim files , the bnhi performs expert reviews on a random sample of every 50 - 100 ambulatory and inpatient claims in each hospital and clinic quarterly , and false reports of diagnosis receive a severe penalty from the bnhi.8 in this study , we used data from the ambulatory care claims ( 2006 - 2007 ) and inpatient claims ( 2006 - 2007 ) and updated registry for beneficiaries ( 2007 ) . all nhi datasets can be linked with each individual 's personal identification number ( pin ) . this study aimed to estimate the recurrent rate of aom in taiwan 's child population and to identify the groups at high risk of recurrence . to meet these goals , we adopted a cohort study design . the study cohort consisted of all 283,084 children who had ambulatory care visits or were hospitalized with a primary or secondary diagnosis of aom ( international classification code 9 version clinical modification ( icd-9-cm ) : 381.xx or 382.xx ) between january 14 and december 31 , 2006 . the dates of their first - time ambulatory care visit or hospitalization in 2006 were set as the baseline ( initial ) aom attack . baseline information was retrieved from claims data , including the patient 's date of birth , gender , place of care ( clinics , district or regional hospitals , medical centers ) , and the specialty of the attending physician . the age of the study subjects was calculated as the difference between the date of the baseline attack and the date of birth . with their unique pins , the individuals who comprised the study cohort could be linked to the 2006 - 2007 ambulatory care and inpatient claims to identify the possible recurrence of aom within 12 months following the baseline attack . only subsequent ambulatory care visits ( or hospitalizations ) with a primary or secondary diagnosis of aom and with a date of ambulatory care visit ( or hospitalization ) at least 15 days apart from the previous aom ambulatory care visit ( or hospitalization ) were considered new episodes ( i.e. , recurrence ) . using the 2007 updated registry for beneficiaries , we were able to calculate the person - years ( pys ) for which each study subject had been observed from the baseline attack either to the date of termination of the nhi policy ( primarily due to death ) or to the 365th day . we then calculated the cumulative incidence rate ( cir ) and incidence density rate ( idr ) per 100 pys for aom within one year of follow - up , according to various subjects ' characteristics . the idr was calculated as the ratio of the total number of aom recurrences ( i.e. , frequency ) to the total number of pys observed . last , we used a multivariate logistic regression model to assess the independent effects of age , gender , place of treatment , and physician specialty on the risk of 1-year aom recurrence . all statistical analyses were performed with sas ( version 9.1 ; sas institute , cary , nc ) . in 2006 , a total of 283,084 children <  =  12 years of age sought treatment for aom , representing an annual incidence rate of 64.5 cases per 1,000 children ( 283,084/4,385,779 ) . the age - specific annual incidence rates for children aged 0 - 2 years , 3 - 5 years , and 6 - 12 years were 71.7 , 158.8 , and 41.0 per 1,000 children , respectively . male children had a higher incidence rate than females ( 67.6 vs. 61.2 per 1,000 ) ( data not shown in tables ) . table 1 shows the characteristics of both the baseline episodes of aom in 2006 and all episodes in one year including baseline attacks and recurrent episodes . the mean ( standard deviation ( sd ) ) age was 4.7 ( 2.8 ) years for the patients at baseline , and male patients predominated ( 54.6% vs. 45.4% ) . nearly 80% of the patients were treated by either otolaryngologists ( 32.2% ) or pediatricians ( 46.3% ) . the distributions of the selected variables were almost the same after inclusion of all recurrent episodes during the study period . the overall idr of recurrence for the study cohort was 33.5 per 100 pys , with the highest idr of 41.2 per 100 pys noted for the patients aged 0 - 2 years . the idr decreased to 38.1 per 100 pys and 26.7 per 100 pys for those aged 3 - 5 and 6 - 12 years , respectively . the recurrence rate was slightly higher in male patients than in female patients ( 34.4 vs. 32.5 per 100 pys ) . additionally , the recurrence rate varied slightly ( 32.7 - 34.4 per 100 pys ) by place of treatment . higher idrs were also noted in patients treated by otolaryngologists ( 34.0 per 100 pys ) and pediatricians ( 34.7 per 100 pys ) ( table 2 ) . table 3 shows the adjusted odds ratios ( ors ) associated with the risk of recurrence in relation to the selected variables of interest . compared with those aged 0 - 2 years , the patients aged 3 - 5 years ( or  =  0.87 , 95% ci  =  0.85 - 0.89 ) and 6 - 12 years ( or  =  0.51 , 95% ci  =  0.50 - 0.52 ) had significantly reduced odds of recurrence . female patients also had significantly lower odds of recurrence than male patients ( or  =  0.92 , 95% ci  =  0.91 - 0.94 ) . additionally , compared with those treated at clinics , patients treated in medical centers ( or  =  0.95 ) and district / regional hospitals ( or  =  0.90 ) had significantly reduced odds of recurrence . moreover , the patients treated by otolaryngologists ( or  =  1.25 , 95% ci  =  1.21 - 1.28 ) , pediatricians ( or  =  1.16 , 95% ci  =  1.13 - 1.18 ) , and family medicine physicians ( or  =  1.08 , 95% ci  =  1.03 - 1.13 ) all had significantly increased odds of recurrence . aom is a public health concern in the pediatric population because of its high incidence and serious adverse outcomes . although the direct costs of diagnosis and treatment for a single episode of aom are not tremendously high , the indirect costs associated with health care for recurrent aom , aom - related complications , and parental absence from work to care for the children can be substantial.1 some epidemiological data are currently available in the literature . reported that the incidence of aom was 0.93 incidents per child - year during the first 24 months of life.2 stangerup et al . estimated that the prevalence of aom was fairly constant at about 25% during the first 5 years of life.3 teele et al . , in a prospective cohort study on children from the greater boston area , reported that by the end of the first year after birth , 62% of children had at least 1 episode of aom ; by the end of the third year of life , the proportion had increased to 83% , and the peak incidence occurred during the first 6 months of life.4 previous studies have also indicated that most children may experience at least 1 episode of aom during their childhood ; between 10% and 62% of children had at least 1 episode of aom by the age of 1 year.1,4,9,10 pukander et al . reported an annual incidence rate of aom of 4.44% in the pediatric population of 2 finnish towns.11 our data were generally compatible with these previous studies . we found that in taiwan , 64.5 per 1,000 children aged 12 or younger may have experienced at least 1 episode of aom in a year . chen et al . examined 3,013 ethnic chinese children ( aged 3 - 6 years ) from 19 daycare centers in kaoshiung city,12 the largest city in southern taiwan , and estimated that the prevalence rate of otitis media was 9.82%.11 however , this cross - sectional survey did not specify the actual prevalence of acute middle ear infection . identified a total of 119,773 cases of aom ( icd-9-cm codes : 381.0 , 381.4 , 382.0 , 382.4 , and 382.9 ) from the 2001 nhi database , and most of the cases were under 5 years of age.13 parnn et al . 's nationwide study focused on patients ' medical utilization and provided limited information on overall and specific rates of prevalence and recurrence . moreover , the diagnostic codes employed by parnn et al . to identify aom were considered inadequate for identification of all aom patients.13   it is generally agreed that the risk of aom may decrease with advanced age during childhood . the peak incidence rate of aom is normally found to occur during the second half of the first year in most studies . estimated that the cir of the first episode of aom was 42.4% ( 95% ci 40.4 - 44.4 ) up to the age of 1 year;2 stangerup et al . reported an incidence rate of 22% , 15% , 10% , and 2% at the age of 1 year , 2 years , 3 - 4 years , and 8 years , respectively.3 our data showed a peak incidence in children aged 3 - 5 years . this finding is compatible with data from other local pneumococcal studies in taiwan . a recent study by wu et al . reported that the peak prevalence of invasive pneumococcal diseases ( lobar pneumonia and empyema ) was in children aged 4 - 5 years.15 another possible explanation for our finding was that many children who sought care for aom at age 3 - 5 years actually incurred this disease at earlier ages . regarding recurrence , our data were compatible with other studies showing that the odds of recurrence decline with age ( idrs of 41.2 per 100 pys for age 0 - 2 years , 38.1 per 100 pys for age 3 - 5 years , and 26.7 per 100 pys for age 6 - 12 years ) . previous studies reached inconsistent conclusions on the effect of gender on the risk of aom.3,4,9,10,14 teele et al.4 and sipila et al.14 found that male gender was a risk factor for aom . in contrast , stangerup et al.,3 homoe et al.,10 and lundgren et al.9 all concluded that no gender differences were found in the incidence and prevalence of aom . our national sample showed that more male than female children ( 54.6% vs. 45.4% ) suffered from aom at baseline , and the incidence rate of aom in 2006 - 2007 was also higher in male children than in their female counterparts ( 67.6 vs. 61.2 per 1,000 ) . additionally , male children were more likely than female children to have recurrent aom ( 34.4 vs. 32.5 per 1,000 pys ) . the plausible mechanisms contributing to the effect of gender on the incidence of aom have not yet been identified . aom is prone to recurrence , and this phenomenon has long been a target of research . traditionally , initial aom attack at an earlier age , comorbid airway infection , sibling aom history , bottle feeding , and daycare condition have been considered risk factors for recurrent aom.4,1618 the recurrence rates reported in previous studies range from 20%- 27% in 6 months16,18 to 60% in 4 months.19 our data showed a recurrence rate of 33.5% in one year in taiwan 's pediatric population , which is somewhat lower than the findings from previous reports . we also found that younger age ( 0 - 2 years ) , male gender , and treatment in clinics were all associated with significantly higher recurrence rates . parnn et al.13 reported that in taiwan , hospital physicians were more likely than clinic physicians to follow the guidelines in treating aom patients . it is not known , however , whether physician nonadherence in clinics contributes to higher recurrence rates among patients treated in clinics . we speculated that the patients cared for by otolaryngology and pediatric specialists had conditions that were more severe than the conditions of those cared for by physicians with other specialties . first , we used the nhi dataset , which is nationally representative and with little risk of selection or recall bias , and there is a low likelihood of lack of response and loss to follow - up of cohort members . second , the use of insurance claim data in clinical research provides easy access to the longitudinal records for a large sample of geographically dispersed patients , which greatly increases the representativeness of the study sample . third , the large number of study subjects also made it possible for us to perform analyses concerning certain variables of interest including age , sex , physician 's specialty , and hospital accreditation . however , findings from the analysis of claims data can be limited by several factors and should be interpreted with caution . first , the accuracy of diagnostic coding from health care providers can affect the validity of data . since 2000 , the bnhi has been using several monitoring and cross - checking mechanisms to ensure the accuracy of diagnostic coding . 8 second , there were no laboratory data or chart information available to determine the disease severity of aom , which might confound the associations of recurrence with selected potential predictors of interest observed in this study . third , we defined  aom episode  as  all visits at least 14 days apart  to overcome the maximum prescription restriction of 3 days for clinics and 7 days for hospitals , but this may cause an underestimation of the actual incidence and recurrence of aom . aom is a public health concern in the pediatric population because of its high incidence and serious adverse outcomes . although the direct costs of diagnosis and treatment for a single episode of aom are not tremendously high , the indirect costs associated with health care for recurrent aom , aom - related complications , and parental absence from work to care for the children can be substantial.1 some epidemiological data are currently available in the literature . reported that the incidence of aom was 0.93 incidents per child - year during the first 24 months of life.2 stangerup et al . estimated that the prevalence of aom was fairly constant at about 25% during the first 5 years of life.3 teele et al . , in a prospective cohort study on children from the greater boston area , reported that by the end of the first year after birth , 62% of children had at least 1 episode of aom ; by the end of the third year of life , the proportion had increased to 83% , and the peak incidence occurred during the first 6 months of life.4 previous studies have also indicated that most children may experience at least 1 episode of aom during their childhood ; between 10% and 62% of children had at least 1 episode of aom by the age of 1 year.1,4,9,10 pukander et al . reported an annual incidence rate of aom of 4.44% in the pediatric population of 2 finnish towns.11 our data were generally compatible with these previous studies . we found that in taiwan , 64.5 per 1,000 children aged 12 or younger may have experienced at least 1 episode of aom in a year . chen et al . examined 3,013 ethnic chinese children ( aged 3 - 6 years ) from 19 daycare centers in kaoshiung city,12 the largest city in southern taiwan , and estimated that the prevalence rate of otitis media was 9.82%.11 however , this cross - sectional survey did not specify the actual prevalence of acute middle ear infection . identified a total of 119,773 cases of aom ( icd-9-cm codes : 381.0 , 381.4 , 382.0 , 382.4 , and 382.9 ) from the 2001 nhi database , and most of the cases were under 5 years of age.13 parnn et al . 's nationwide study focused on patients ' medical utilization and provided limited information on overall and specific rates of prevalence and recurrence . moreover , the diagnostic codes employed by parnn et al . to identify aom were considered inadequate for identification of all aom patients.13 it is generally agreed that the risk of aom may decrease with advanced age during childhood . the peak incidence rate of aom is normally found to occur during the second half of the first year in most studies . estimated that the cir of the first episode of aom was 42.4% ( 95% ci 40.4 - 44.4 ) up to the age of 1 year;2 stangerup et al . reported an incidence rate of 22% , 15% , 10% , and 2% at the age of 1 year , 2 years , 3 - 4 years , and 8 years , respectively.3 our data showed a peak incidence in children aged 3 - 5 years . a recent study by wu et al . reported that the peak prevalence of invasive pneumococcal diseases ( lobar pneumonia and empyema ) was in children aged 4 - 5 years.15 another possible explanation for our finding was that many children who sought care for aom at age 3 - 5 years actually incurred this disease at earlier ages . regarding recurrence , our data were compatible with other studies showing that the odds of recurrence decline with age ( idrs of 41.2 per 100 pys for age 0 - 2 years , 38.1 per 100 pys for age 3 - 5 years , and 26.7 per 100 pys for age 6 - 12 years ) . previous studies reached inconsistent conclusions on the effect of gender on the risk of aom.3,4,9,10,14 teele et al.4 and sipila et al.14 found that male gender was a risk factor for aom . in contrast , stangerup et al.,3 homoe et al.,10 and lundgren et al.9 all concluded that no gender differences were found in the incidence and prevalence of aom . our national sample showed that more male than female children ( 54.6% vs. 45.4% ) suffered from aom at baseline , and the incidence rate of aom in 2006 - 2007 was also higher in male children than in their female counterparts ( 67.6 vs. 61.2 per 1,000 ) . additionally , male children were more likely than female children to have recurrent aom ( 34.4 vs. 32.5 per 1,000 pys ) . the plausible mechanisms contributing to the effect of gender on the incidence of aom have not yet been identified . aom is prone to recurrence , and this phenomenon has long been a target of research . traditionally , initial aom attack at an earlier age , comorbid airway infection , sibling aom history , bottle feeding , and daycare condition have been considered risk factors for recurrent aom.4,1618 the recurrence rates reported in previous studies range from 20%- 27% in 6 months16,18 to 60% in 4 months.19 our data showed a recurrence rate of 33.5% in one year in taiwan 's pediatric population , which is somewhat lower than the findings from previous reports . we also found that younger age ( 0 - 2 years ) , male gender , and treatment in clinics were all associated with significantly higher recurrence rates . parnn et al.13 reported that in taiwan , hospital physicians were more likely than clinic physicians to follow the guidelines in treating aom patients . it is not known , however , whether physician nonadherence in clinics contributes to higher recurrence rates among patients treated in clinics . we speculated that the patients cared for by otolaryngology and pediatric specialists had conditions that were more severe than the conditions of those cared for by physicians with other specialties . first , we used the nhi dataset , which is nationally representative and with little risk of selection or recall bias , and there is a low likelihood of lack of response and loss to follow - up of cohort members . second , the use of insurance claim data in clinical research provides easy access to the longitudinal records for a large sample of geographically dispersed patients , which greatly increases the representativeness of the study sample . third , the large number of study subjects also made it possible for us to perform analyses concerning certain variables of interest including age , sex , physician 's specialty , and hospital accreditation . however , findings from the analysis of claims data can be limited by several factors and should be interpreted with caution . first , the accuracy of diagnostic coding from health care providers can affect the validity of data . since 2000 , the bnhi has been using several monitoring and cross - checking mechanisms to ensure the accuracy of diagnostic coding . 8 second , there were no laboratory data or chart information available to determine the disease severity of aom , which might confound the associations of recurrence with selected potential predictors of interest observed in this study . third , we defined  aom episode  as  all visits at least 14 days apart  to overcome the maximum prescription restriction of 3 days for clinics and 7 days for hospitals , but this may cause an underestimation of the actual incidence and recurrence of aom . despite differences in incidence rates of aom between our study and findings from previous studies that are mainly due to differences in diagnosis criteria , sampling methods , observation intervals , and population characteristics , we still found that aom remains a major threat to children 's health in taiwan . a total of 283,084 children <  =  12 years of age sought treatment for aom in 2006 in taiwan , representing an annual incidence rate of 64.5 per 1,000 children . we also found that the overall idr of recurrence was high at 33.5 per 100 pys , which requires attention from clinicians and health care administrators . we therefore suggest that more intensive ontological care should be delivered to children with elevated risk of recurrence including males , those aged 0 - 2 years , those treated at clinics , and those cared for by otolaryngologists or pediatricians . this study is based in part on data from the national health insurance research database provided by the bureau of national health insurance , department of health and managed by national health research institutes . the interpretation and conclusions contained herein do not represent those of bureau of national health insurance , department of health or national health research institutes of taiwan , republic of china .
objective : to report the incidence and recurrence of acute otitis media ( aom ) in taiwan 's pediatric population.methods:information from children ( aged <  =  12 years ) with a diagnosis of aom was retrieved from the 2006 national healthcare insurance claims database . 
 we calculated the cumulative incidence rate and the incidence density rate of recurrent aom within one year after the initial diagnosis in 2006 . 
 we used a multivariate logistic regression model to assess the predictors for recurrence of aom.results:the annual incidence rate of aom was estimated to be 64.5 cases per 1,000 children . 
 the overall one - year cumulative incidence rate of recurrence was 33.1% , and the incidence density rate was 33.5 cases per 100 person - years , with the highest figure ( 41.2 cases per 100 person - years ) noted for children aged 0 - 2 years . 
 recurrence was significantly associated with age , gender , place of treatment , and physician specialty.conclusion:aom remains a major threat to children 's health in taiwan . 
 male children and very young children require more aggressive preventive strategies to reduce the risk of recurrence .