multimorbidity , defined as two or more coexisting chronic conditions within an individual , is a growing phenomenon in ageing societies and is especially prevalent in older age groups [ 24 ] . multimorbidity makes management of chronic conditions by clinicians more complex ; they often lack evidence on the best care strategies to follow with this type of patient . in fact , clinical guidelines rarely address multimorbidity and clinical trials often exclude comorbid and older patients [ 5 , 6 ] . individuals manifesting multimorbidity are typically associated with higher degrees of disability , lower quality of life , greater psychological distress and mortality risk [ 79 ] , and increased use of health ( and social ) care [ 10 , 11 ] services than if we considered these chronic conditions in isolation or individuals with a single chronic condition . it is of particular relevance for patients , their carers , and healthcare providers , but increasingly a concern for policy makers and societies as a whole . therefore , it is widely accepted that health systems need to focus their strategies in organising healthcare provision and planning for multimorbid patients and pay attention to the implications on treatment patterns and combinations [ 12 , 13 ] . because of its worldwide prevalence , osteoporosis is also considered a serious public health concern . ageing of populations worldwide will be responsible for a major increase in the incidence of osteoporosis in postmenopausal women . the quality of life of postmenopausal women with osteoporosis is adversely affected if they have bone fractures and pain . previous studies by this research group have revealed high levels ( 91% ) of coexisting disease among women with osteoporosis over 65 years old . furthermore , osteoporosis and bronchiectasis are the only two diseases , out of a list of 52 , disproportionally more prevalent among women living in richer areas in the basque country . the presence of coexisting conditions in women with osteoporosis has been revealed to reduce health - related quality of life , increase the risk of vertebral fractures , and contribute to mortality [ 17 , 18 ] . the aim of this study was to establish the prevalence of multimorbidity in women with osteoporosis living in the basque country , to categorise the number and types of additional chronic conditions recorded , and to report the demographic and socioeconomic characteristics ( age and deprivation index ) . a descriptive study was carried out which included all women aged 45 and above with at least one chronic condition ( n = 397,940 ) who were covered by public health insurance in the basque country on 31st august 2011 and who had been covered for at least 6 months in the previous year , regardless of whether or not they had made any contact with or use of the basque health service - osakidetza . the study compared those women with an osteoporosis diagnosis ( n = 52,844 ) versus those women without a diagnosis of osteoporosis ( n = 345,096 ) . therefore , we observed almost all of the inhabitants of the basque country , by census data in addition to irregular immigrants who have a health identification card and have used the healthcare system during the study period . our dataset is derived from the database set up by the population stratification programme ( prest ) of osakidetza . in addition , in osakidetza , diagnoses are coded according to international classification of diseases ( icd-9-mc ) , while the anatomical , therapeutic , chemical ( atc )   coding system is used for drugs prescribed by primary care doctors . with this information , citizens in the basque country are classified annually using acgs ( adjusted clinical groups ) , a case mix system developed at the johns hopkins university , which enables health problems to be identified from diagnoses and prescriptions , in addition to categorising citizens according to their healthcare needs and cost into a hundred groups . with the aim of studying multimorbidity and comorbidity of chronic diseases and osteoporosis , we adopted a list of 52 pathologies , defined by consensus among the research team . this task was based on adapting two preexisting lists , published by other authors , the 40 diseases selected by barnett et al . ( 2012 )   and the conditions considered to be chronic in the acg technical reference guide . a detailed description of this dataset can be found in a previously published article . from the aforementioned list , we omitted four pathologies ,  attention deficit disorder ,   intellectual disability ,   anorexia and bulimia  because these diagnoses are very rare in the age group under study , and therefore , our definitive list was comprised of 47 chronic conditions . as a social indicator , the deprivation index of census tract was used . a tract is the smallest geographical unit ( n = 1200 habitants ) in which population census data can be broken down ; this was created according to population size , geographical , and urban criteria . as the tracts are so small , they tend to be quite homogeneous with respect to the type of dwellings . the deprivation index is an ordinal variable , categorised into five levels , which provides a measure of the socioeconomic characteristics of census tracts and is drawn from the following factors : manual workers , unemployment , temporary employees , and inadequate level of education in the population overall and in young people . we measured health care provision in terms of cost - weighted utilisation of health care . health care use was estimated for a 12-month period ( from 1 september 2010 to 31 august 2011 ) . we consider the cost of the following types of services separately : primary care ( including visits to physicians and nurses , laboratory test , and radiology examinations ) , specialised outpatient care ( visits to specialists , rehabilitation , dialysis , radiotherapy , and chemotherapy services ) , inpatient stays , emergency department attendance , and prescribing . in the case of prescribing , the cost was computed directly from primary care prescriptions recorded in the electronic health records . for other types of use , the costs of hospitalisation and outpatient surgery were calculated in relation to their weight in the corresponding diagnosis related groups ( drgs ) . information on some services was not available and these were therefore excluded from the analysis , admission to psychiatric hospitals , home hospitalisation and day care services ( except for procedures and services listed above ) , health care transport , and prostheses and other equipment provided to patients at home . the prevalence of osteoporosis stratified by age group and deprivation index was obtained ; the nonparametric kruskal - wallis test was applied to see whether there were differences between these groups . the number of chronic comorbidities for women with osteoporosis was calculated ; this was compared against the chronic women without osteoporosis by the nonparametric wilcoxon mann - whitney test . in addition , the average of chronic diseases for women with osteoporosis and without osteoporosis aged > 44 , stratified by deprivation index , was performed . the 47 risk ratios for the list of chronic conditions with osteoporosis as comorbidity were calculated . moreover , the average of the observed healthcare costs in women with osteoporosis was obtained . statistical calculations were performed using stata , data analysis and statistical software , release 12 ( statacorp , lp , college station , tx , usa ) . out of 579,575 women above 44 years , 52,844 ( 9.12% ) presented osteoporosis .   table 1 shows the prevalence and distribution of women with osteoporosis according to age band and deprivation index . it can be observed that the higher percentage of these is aged 55 to 64 ( 24.73% ) and furthermore the prevalence of this disease increased up to the age of 80 . as for the deprivation index we observed that osteoporosis presents more commonly in women with a higher socioeconomic level ( 24.50% ) . the prevalence of osteoporosis was higher among rich people . however , no decreasing gradient was observed . after applying the nonparametric kruskal - wallis test , statistically significant differences were obtained between the different age bands ( p < 0.001 ) and between the different deprivation index groups ( p < 0.001 ) . table 2 shows the number of chronic pathologies for women with and without osteoporosis ; the latter subgroup was comprised of 345,096 women . it was observed that only 14.96% of women with osteoporosis only suffer from this chronic disease compared to 36.59% of chronic women over 44 without osteoporosis . it is notable that 1.47% of women with osteoporosis have 10 or more chronic pathologies , compared to 0.35% of women without osteoporosis . the difference in the distribution of the number of chronic pathologies between these two groups was statistically significant ( p < 0.001 ) . therefore , it can be stated that 85.04% of women with osteoporosis and 63.41% of women without osteoporosis over 44 have multimorbidity . figure 1 shows the average of the number of chronic pathologies of women over 44 with and without osteoporosis by age and figure 2 shows the average of the number of chronic pathologies by deprivation index in the same groups . as can be observed , this average increased with age and socioeconomic index and was higher in more depressed areas . comparing both groups , the chronic women without osteoporosis have higher chronic condition average until 75 years however , from socioeconomic levels 2 to 5 , women with osteoporosis have greater chronic condition averages . the association between osteoporosis and other chronic conditions was statistically significant in 38 of them . the people with osteoporosis have nearly two times more risk of suffering bronchiectasis ( 1.7 ) than women without osteoporosis . however , women with osteoporosis have less risk of having diabetes ( 0.65 ) than women without osteoporosis . regarding cost analysis by deprivation index , we checked that , as socioeconomic level reduces , healthcare costs increase in women with osteoporosis both with one pathology and as the number of these pathologies increases ( see figure 3 ) . this population - based study covering the whole female population over 44 years of a large region analysed the prevalence of multimorbidity in this population and indicated that 85.04% of women in this age group with osteoporosis have multimorbidity . these figures are much higher than those found in other studies performed with a spanish population in which the prevalence of multimorbidity is approximately 30% . these differences may be because of the difference in methodologies used , which makes comparison of results difficult . in contrast , the prevalence of osteoporosis is less than that found in other studies , also performed on a spanish population . the results reveal that osteoporosis , when presented in an isolated manner , appears more prevalent , or at least more diagnosed , in people with a high socioeconomic level . these data coincide with those of other studies that reveal the presence of a relationship between socioeconomic level and multimorbidity [ 2730 ] . the prevalence of osteoporosis increases with age up to 85 + years where it plateaus and declines . this pattern was also seen for most chronic conditions in the basque country   but another study shows the contrary   in the oldest women in canada . we have seen that the fact that a woman had osteoporosis increased the risk of having other musculoskeletal disorders . these results coincide with those found in other studies performed in the basque country , where we observe that people with a low socioeconomic level use more health resources ; that is , inequality in favour of the poor seems to be within osakidetza . these data could be accounted for by the fact that people with more financial resources use private healthcare to a greater extent than the least affluent to avoid waiting lists [ 31 , 32 ] . perhaps the greater use of private healthcare can also account for the higher prevalence of osteoporosis present at higher socioeconomic levels , not because of the actual presence of more osteoporosis in this population but rather because this diagnosis is made more commonly in private healthcare . a difference between this study and others found in the literature is that the study is performed using data from a health system with universal cover ; this includes virtually the entire basque country population which reduces the bias that could occur using a restricted population sample . the database used contains primary care , specialised care , and outpatient hospital care information . this use of different data sources reduces the imprecision that could arise in the calculations [ 33 , 34 ] and leads to a better description of health problems . given that the administrative databases only contain information on those patients who have requested healthcare , the prevalence obtained only reflects known cases . those cases , where professionals or patients are unaware , have been excluded ; and this is commonplace in the case of osteoporosis . another limitation is the fact that there is no access to information from private health sector resources . therefore , there are no data on monitoring of the disease in this sector . finally , since we use a socioeconomic index collected through area of residence , our study has the limitations of ecological studies . because osteoporosis usually presents together with other chronic diseases , it is important for clinicians to consider the interactions that other multimorbid pathologies and their treatments can have on this . its onset , frequently insidious , may mean that treatment is focused on another more serious chronic pathology , leaving osteoporosis and its treatment to one side . however , this disease is a significant health problem because of the serious consequences of bone fractures . with the ageing of the population , it is expected that the number of fractures will increase considerably over the next few years along with healthcare costs . suitable treatment of multimorbidity in people who suffer from osteoporosis , which slows down course and prevents fractures , is a challenge for health systems . a high percentage of women with an osteoporosis diagnosis presents at least one other chronic disease and the prevalence of multimorbidity is much higher in women with disadvantaged socioeconomic levels . the comorbidity present in osteoporosis patients should be considered for both correct clinical management and setting up suitable treatments and when drawing up health policies .
objectives . this study aimed to establish the prevalence of multimorbidity in women diagnosed with osteoporosis and to report it by deprivation index . the characteristics of comorbidity in osteoporotic women 
 are compared to the general female chronic population , and the impact on healthcare expenditure of this population group is estimated . methods . a cross - sectional analysis that included all basque country women aged 45 years and over ( n = 579,575 ) 
 was performed . 
 sociodemographic , diagnostic , and healthcare cost data were extracted from electronic databases for a one - year period . 
 chronic conditions were identified from their diagnoses and prescriptions . 
 the existence of two or more chronic diseases out of a list of 47 was defined as multimorbidity . 
 results . 
 9.12% of women presented osteoporosis and 85.04% of them were multimorbid . 
 although multimorbidity in osteoporosis increased with age and deprivation level , prevalence was higher in the better - off groups . 
 women with osteoporosis had greater risk of having other musculoskeletal disorders but less risk of having diabetes ( rr = 0.65 ) than chronic patients without osteoporosis . 
 people with poorer socioeconomic status had higher healthcare cost . conclusions . 
 most women with osteoporosis have multimorbidity . 
 the variety of conditions emphasises the complexity of clinical management in this group and the importance of maintaining a generalist and multidisciplinary approach to their clinical care .