only. Powered by TCPDF (www.tcpdf.org) Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com Dovepress Dovepress 222 Ponjoan et al Figure 2 Incidence rate (A) and prevalence (B) of dementia. Note: According to sex (green line, women; blue line, men; red line, overall population) by age-group in Catalan population aged at least 65 years. 0 (65–69) (70–74) (75–79) (80–84) Age group (years) (85–89) (≥90) (65–69) (70–74) (75–79) (80–84) Age group (years) (85–89) (≥90) 10 20 30 A BIncidence (×1,000/person-years) 0 5 10 15 20 Prevalence (%) Clinical Epidemiology downloaded from https://www.dovepress.com/ by 76.229.153.206 on 05-Dec-2021 For personal use only. Powered by TCPDF (www.tcpdf.org) Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com Dovepress Dovepress 223 Ponjoan et al years.32–35 At the European level, age- and sex-standardized prevalence of dementia was estimated at 6.4% by a collaborative study of population-based cohorts conducted in the 1990s,36 7.3% by a meta-analysis that integrated studies conducted from 1980 until 2004,37 and 7.1% based on a meta-analysis on data obtained mainly during the 1990s and 2000s.38 More recent national estimates have been 6.5% in the UK,39 3.65% in Portugal,40 or 5.0% in Greece.41 Our prevalence estimation fell in the lower range of published results from the 1990s and early 2000s in face-to-face studies in Spain and in the European population, and were in line with the most recent estimations. The prevalence of dementia has been reported to be decreasing in high-income countries,42 the USA,43 the UK,39 and Spain.44 However, comparisons between studies are difficult to make, because of methodological differences. Therefore, it is plausible that our 2016 estimates reflect a reduction in dementia cases since the 1990s or 2000s, but we cannot reject other explanations. Population characteristics could be a factor. For example, most of the population in Catalonia is bilingual in Catalan and Spanish. Bilingualism may contribute to cognitive reserve and protect against the onset of dementia,45 and could have affected our estimates. SIDIAP does not provide data on languages spoken by patients. Electronic health records In a comparison with other studies based on electronic health records, our findings provided new insights about the epidemiology of dementia. Our results were similar to those reported by a study that used diagnoses and drugprescription data from primary-care and pharmacy electronic databases to estimate unadjusted prevalence as 5.91% (95% CI 5.85%–5.95%) in persons at least 65 years old living in Madrid in 2011.6 However, our estimates were higher than previous studies in other European populations. A Danish study estimated the prevalence of dementia at 3.8% using electronic health records from secondary-care settings.46 Another study, by Perera et al, compiled data from six electronic health-record systems, including both primary and secondary care from different European countries, to estimate prevalence and incidence rates of dementia.7 They reported lower incidence and prevalence estimates in all age-groups than the ones we observed. Such differences remained for estimates restricted to data from primary-care settings, Table 2 Description of the characteristics of the primary care settings in Catalonia (Spain) in relation to dementia assessment Dementia assessment Study population (n=1,048,956), n (%) Dementia-free sex-standardized; b age-standardized; c sex-standardized. Clinical Epidemiology downloaded from https://www.dovepress.com/ by 76.229.153.206 on 05-Dec-2021 For personal use only. Powered by TCPDF (www.tcpdf.org) Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com Dovepress Dovepress 224 Ponjoan et al which contained fewer dementia cases than SIDIAP. These differences might be partially explained by methodological issues, demographic aspects, and characteristics of primarycare settings. Our methodology applied a mixed definition of dementia that included not only diagnosis but also prescription or billing of antidementia drugs. This broader definition might capture more dementia cases