Abstract
BackgroundDespite worldwide recognition of the burden of dementia, no epidemiological data is yet available in Portugal. The objective of this study is to estimate the prevalence and describe the pattern of cognitive impairment with dementia or no dementia (CIND) in rural and urban populations from Northern Portugal.MethodsTwo random samples of residents aged 55 to 79 years in rural and urban communities were drawn from the health centres registries to be screened for cognitive impairment. The screening criteria for dementia were an abnormal Mini-Mental State Examination (MMSE) score or a Blessed Dementia Scale score. After excluding those who tested positive for dementia, cut-off points for CIND were set at 1 standard deviation below the mean of the MMSE according to educational level. All those who screened positive either for dementia or CIND were examined by a neurologist for establishing a definitive diagnosis.ResultsThe prevalence of cognitive impairment was higher in rural than in urban populations, 16.8% (95% CI: 14.3-19.8%) vs. 12.0% (95%CI: 9.3-15.4%), with a rural/urban prevalence ratio (PR) of 2.16 (95% CI: 1.04-4.50) in the eldest and 2.19 (95% CI: 1.01-4.76) in persons with vascular risk factors. The prevalence of dementia was 2.7% (95% CI: 1.9-3.8%) with a rural/urban PR = 2.1 and the prevalence of CIND was 12.3% (95% CI: 10.4-14.4%) and PR = 1.3. The prevalence of dementia increases exponentially with age and in those with cerebrovascular disease or other comorbid conditions while the prevalence of CIND, besides these factors, is also higher in persons with low levels of education or vascular risk factors. Alzheimer's and vascular disease were equally likely aetiologies of dementia (38.7%), the later more common in men PR(F:M = 0.3) as opposed to the former PR(F:M = 2.0). Vascular CIND, associated either with cerebrovascular disease or vascular risk factors was more frequent (39.7%) then depression (18.4%) or any other aetiology.ConclusionsThe prevalence of cognitive impairment is higher in rural compared with urban populations. This is shown in the synergy between age and rurality, with the rural/urban prevalence ratio increasing with age. In this relatively young population from Northern Portugal, cerebrovascular disease as well as vascular risk factors account for 48% of overall cognitive impairment.
Highlights
Despite worldwide recognition of the burden of dementia, no epidemiological data is yet available in Portugal
In general there is a higher prevalence of cognitive impairment in rural compared to urban populations for all population strata considered, reaching the highest prevalence ratios in the oldest (2.16), illiterate (2.05) and dependent (2.21)
Since age is the more important predictor of cognitive impairment and the age distribution of men and women participants and non-participants from both rural and urban areas was not significantly different and similar to the population of the 2001 Census, the overall estimates of dementia and cognitive impairment with dementia or no dementia (CIND) should mirror the urban/rural mix in whole Portugal. To our knowledge, this is the first study to assess the prevalence of cognitive loss in the Portuguese population, and the results corroborate the expected high prevalence of cognitive impairment (CIND and dementia), as much as the assumption that Portugal may be a paradigmatic example for regional variations in dementia among other countries, both in terms of rural-urban environments and socio-cultural disparities
Summary
Despite worldwide recognition of the burden of dementia, no epidemiological data is yet available in Portugal. The objective of this study is to estimate the prevalence and describe the pattern of cognitive impairment with dementia or no dementia (CIND) in rural and urban populations from Northern Portugal. Stroke and TIA incidences in rural northern Portugal are known to rank among the highest reported in community-based studies [6,7], probably resulting from the high prevalence of arterial hypertension [8], with a higher risk for cognitive impairment, either of Alzheimer or vascular type, associated with vascular risk factors [9,10,11,12,13]. Portugal is supposed to have social, cultural and economical idiosyncrasies which could hypothetically justify a high prevalence of cognitive impairment and dementia, no population study has ever been taken to prove so. Recognition of the effects of such contrasts in the risk of cognitive impairment may justify different interventions and allocation of resources in rural and urban areas
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