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Prospective studies suggest that memory deficits are detectable decades before clinical symptoms of dementia emerge. However, individual differences in long-term memory trajectories prior to diagnosis need to be further elucidated. The aim of the current study was to investigate long-term dementia and mortality risk for individuals with different memory trajectory profiles in a well-characterized population-based sample.
1062 adults (aged 45–80 years) who were non-demented at baseline were followed over 23–28 years. Dementia and mortality risk were studied for three previously classified episodic memory trajectory groups: maintained high performance (Maintainers; 26%), average decline (Averages; 64%), and accelerated decline (Decliners; 12%), using multistate modeling to characterize individuals’ transitions from an initial non-demented state, possibly to a state of dementia and/or death.
The memory groups showed considerable intergroup variability in memory profiles, starting 10–15 years prior to dementia diagnosis, and prior to death. A strong relationship between memory trajectory group and dementia risk was found. Specifically, Decliners had more than a fourfold risk of developing dementia compared to Averages. In contrast, Maintainers had a 2.6 times decreased dementia risk compared to Averages, and in addition showed no detectable memory decline prior to dementia diagnosis. A similar pattern of association was found for the memory groups and mortality risk, although only among non-demented.
There was a strong relationship between accelerated memory decline and dementia, further supporting the prognostic value of memory decline. The intergroup differences, however, suggest that mechanisms involved in successful memory aging may delay symptom onset.
The objective was to examine whether aspects of social relationships in old age are associated with all-cause dementia and Alzheimer's disease (AD).
We studied 1,715 older adults (≥ 65 years) who were dementia-free at baseline over a period of up to 16 years. Data on living status, contact/visit frequency, satisfaction with contact frequency, and having/not having a close friend were analyzed using Cox proportional hazards regressions with all-cause dementia or AD as the dependent variable. To control for reverse causality and to identify potential long-term effects, we additionally performed analyses with delayed entry.
We identified 373 incident cases of dementia (207 with AD) during follow-up. The variable visiting/visits from friends was associated with reduced risk of all-cause dementia. Further, a higher value on the relationships index (sum of all variables) was associated with reduced risk of all-cause dementia and AD. However, in analyses with delayed entry, restricted to participants with a survival time of three years or more, none of the social relationship variables was associated with all-cause dementia or AD.
The results indicate that certain aspects of social relationships are associated with incident dementia or AD, but also that these associations may reflect reverse causality. Future studies aimed at identifying other factors of a person's social life that may have the potential to postpone dementia should consider the effects of reverse causality.
This study examines the association between marital and parental status and their individual and combined effect on risk of dementia diseases in a population-based longitudinal study while controlling for a range of potential confounders, including social networks and exposure to stressful negative life events.
A total of 1,609 participants without dementia, aged 65 years and over, were followed for an average period of 8.6 years (SD = 4.8). During follow-up, 354 participants were diagnosed with dementia. Cox regression was used to investigate the effect of marital and parental status on risk of dementia.
In univariate Cox regression models (adjusted for age as time scale), widowed (hazard ratio (HR) 1.42, 95% confidence interval (CI) = 1.13–1.78), and not having children (HR 1.54, 95% CI = 1.15–2.06) were significantly associated with incident dementia. In multivariate analyses that included simultaneously marital and parental status and covariates that were found to be significant in univariate models (p < 0.10), the HR was 1.30 (95% CI = 1.01–1.66) for widowed, and 1.51 (95% CI = 1.08–2.10) for those not having children. Finally, a group of four combined factors was constructed: married parents (reference), married without children, widowed parents, and widowed without children. The combined effect revealed a 1.3 times higher risk (95% CI = 1.03–1.76) of dementia in widow parents, and a 2.2 times higher risk (95% CI = 1.36–3.60) in widowed persons without children, in relation to married parents. No significant difference was observed for those being married and without children.
Our findings suggest that marital- and parental status are important risk factors for developing dementia, with especially increased risk in those being both widowed and without children.
The impact of stressful life events as a risk factor of dementia diseases is inconclusive. We sought to determine whether stressful negative life events are associated with incidental dementia in a population-based study with long-term follow-up. We also tested the hypothesis that the occurrence of positive life events could mitigate or overcome the possible adverse effects of negative life events on dementia conversion.
The study involved 2,462 dementia-free participants aged 55 years and older. Information on life events was ascertained at baseline from a comprehensive Life Event Inventory, which included 56 questions about specific life events. For each life event, the emotional impact (both positive and negative) and emotional adjustment were asked for.
During follow-up, 423 participants developed dementia; of these, 240 developed Alzheimer's disease (AD). Cox regression analysis showed no association between the total number of negative life events and the incidence of dementia when adjusted solely for age and gender (hazard ratio = 0.97, 95% CI = 0.92–1.02), or with multiple adjustments for a range of covariates (hazard ratio = 0.96, 95% CI = 0.91–1.01). Similarly, neither emotional impact nor emotional adjustment to these life events was associated with incident dementia. A separate analysis of AD did not alter the results.
The result of this population-based study finds no association between negative or positive life events and dementia. Accordingly, our results reject the hypothesis that stressful life events trigger the onset of dementia diseases.
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