Abstract
Background Sleep disturbance is suggested to contribute to the
development of dementia. However, prospective longitudinal data from
middle-aged populations are scarce.
Methods We investigated a population-based sample of 2386 men aged 42-62
years at baseline during 1984-1989. Participants having a history of
mental illnesses, psychiatric medication, Parkinson's disease or
dementia within 2 years after baseline (n=296) were excluded. Difficulty
falling asleep or maintaining sleep, sleep duration and daytime
tiredness were enquired. Dementia diagnoses (n=287) between 1984 and
2014 were obtained through linkage with hospital discharge, national
death and special reimbursement registers. Cox proportional hazards
analyses were performed for all dementias, and separately for
Alzheimer's disease (n=234) and other phenotypes (n=53). Additional
analyses were performed on a subsample of an apolipoprotein E (APOE)
genotype-tested population (n=1199).
Results The risk ratio for dementia was 1.58 (95% CI 1.10 to 2.27) in
men with frequent sleep disturbance after adjustments for age,
examination year, elevated depressive symptoms, physical activity,
alcohol consumption, cumulative smoking history, systolic blood
pressure, body mass index, low-density lipoprotein and high-density
lipoprotein cholesterol, high-sensitivity C reactive protein,
cardiovascular disease history, education years and living alone.
Daytime tiredness and sleep duration were not associated with dementia
in adjusted analysis. In the APOE subsample, both APOE epsilon 4
genotype and frequent sleep disturbance were associated with increased
dementia risk, but in the interaction analysis they had no joint effect.
Conclusions Self-reported frequent sleep disturbance in middle-aged men
may relate to the development of dementia in later life. Having an APOE
e4 genotype did not affect the relationship.