The Role of Lifestyle Factors and Sleep Duration for Late-Onset Dementia: A Cohort Study

Background: The role of lifestyle factors and sleep for dementia is uncertain. Objective: To examine the associations of major lifestyle factors and sleep duration with risk of late-onset dementia. Methods: We used data from a population-based cohort of 28,775 Swedish adults who were >= 65 years of age and completed a questionnaire about lifestyle and other modifiable factors in the autumn of 1997. Dementia cases were ascertained by linkage with the Swedish National Patient Register. Results: During a mean follow-up of 12.6 years, dementia was diagnosed among 3,755 participants (mean age at diagnosis 83.2 +/- 5.1 years). There were no associations of an overall healthy diet (defined by a modified Dietary Approaches to Stop Hypertension Diet score or a Mediterranean diet score), alcohol and coffee consumption, or physical activity with dementia incidence. Compared with never smokers, dementia risk was increased in former and current smokers (hazard ratio [95% confidence interval] = 1.13 [1.04-1.23] and 1.10 [1.00-1.21], respectively). Extended time of sleep (>9 h per night) was associated with an increased risk of dementia. However, this association appeared to be related to a reverse causation effect since the association did not remain after exclusion of cases diagnosed within the first five or ten years of follow-up. Conclusions: This study found no evidence that major lifestyle factors, aside from smoking, or sleep duration influence the risk of dementia.