Decreasing prevalence of dementia in 85-year olds examined 22 years apart: the influence of education and stroke

Abstract

Individuals aged 80 years and older constitute the fastest growing segment of the population worldwide, leading to an expected increase in dementia cases. Education level and treatment of vascular risk factors has increased during the last decades. We examined whether this has influenced the prevalence of dementia according to DSM-III-R using population-based samples of 85-year-olds (N = 1065) examined with identical methods 1986–87 and 2008–10. The prevalence of dementia was 29.8% in 1986–87 and 21.7% in 2008–10 (OR 0.66; 95%-CI: 0.50–0.86). The decline was mainly observed for vascular dementia. The proportion with more than basic education (25.2% and 57.7%), and the prevalence of stroke (20% and 30%) increased, but the odds ratio for dementia with stroke decreased from 4.3 to 1.8 (interaction stroke*birth cohort; p = 0.008). In a logistic regression, education (OR 0.70; 95%-CI 0.51–0.96), stroke (OR 3.78; 95%-CI 2.28–6.29), interaction stroke*birth cohort (OR 0.50; 95%-CI 0.26–0.97), but not birth cohort (OR 0.98; 95%-CI 0.68–1.41), were related to prevalence of dementia. Thus, the decline in dementia prevalence was mainly explained by higher education and lower odds for dementia with stroke in later born birth cohorts. The findings may be related to an increased cognitive reserve and better treatment of stroke in later-born cohorts.

Is the prevalence of psychosis in the very old decreasing? A comparison of 85‐year‐olds born 22 years apart

“…Nonparticipants and participants did not differ regarding sex or hospital discharge diagnoses for cardiovascular disorders, stroke, or mental disorders. However, nonparticipants had lower survival until age 88 years (76.7% versus 83.4%; P = .011), and higher prevalence of depression in the hospital discharge register (3.5% versus 1.2%; P = .022) .…”

“…Each symptom had to attain a level causing significant difficulties in social life. The final diagnosis of dementia was made by the last author if the participant had dementia according to both sources of information, or if the participant had dementia according to one of the examinations and the other examination gave evidence of subthreshold symptoms of dementia . Thus, individuals with subthreshold dementia based on the psychiatric examination and a history of decline in cognitive function compatible with dementia according to key informants were classified with dementia.…”

“…A reflection of this may be the emerging evidence that the incidence and prevalence of dementia is decreasing in high‐income countries . We have recently reported that the prevalence of dementia among 85‐year‐olds decreased from 30% to 22% between 1986 to 1987 and 2008 to 2010 . Based on these notions, we hypothesized that there could also be a decrease in the prevalence of psychotic symptoms among individuals without dementia.…”

Age‐Normative MMSE Data for Older Persons Aged 85 to 93 in a Longitudinal Swedish Cohort

“…In an additional longitudinal (but not normative) study of very old age of the same age cohorts, mean MMSE values for 97, 99, and 100 years of age were around 17 . In a study of 85‐year‐olds born in 1923‐1924, the MMSE mean values were significantly (approximately 1.5 points) higher than for those born 22 years earlier in 1901, suggesting improvements over time between age cohorts …”

The Importance of Birth Year for the Incidence of Dementia

“…Few studies have been concerned with the effect of birth year on dementia prevalence and incidence. In the Gothenburg H70 Birth Cohort Studies, we observed a decrease in the prevalence of dementia between 85‐year‐old people born in 1901 to 1902 and those born in 1923 to 1924 (from 30% to 22%) . This was, to a large extent, explained by the higher educational level in the later‐born cohort, but also by a decreased association between stroke and dementia, leading to a larger decrease in vascular dementia.…”