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Sleep duration as risk factors for dementia and premature death

Short and long daily sleep duration were risk factors for dementia and premature death in a study of Japanese adults aged 60 years and older, a study by researchers at the Kyushu UniversityFukuoka, Japan have found.

Among 1,517 adults who were followed for 10 years, 294 developed dementia and 282 died. Age- and sex-adjusted incidence rates of dementia and all-cause mortality were greater in those with daily sleep duration of less than 5.0 hours and 10.0 hours or more, compared with those with daily sleep duration of 5.0 to 6.9 hours. Participants with short sleep duration who had high physical activity did not have a greater risk of dementia and death, however.

"Given the beneficial effects of physical activity on risk of sleep disturbance, these findings indicate that not only maintenance of appropriate sleep duration, but also modification of lifestyle behaviours related to sleep may be an effective strategy for preventing dementia and premature death in elderly adults," the authors wrote.

Abstract
Objectives: To investigate the association between daily sleep duration and risk of dementia and death in a Japanese elderly population.
Design: Prospective cohort study.
Setting: The Hisayama Study, Japan.
Participants: Community‐dwelling Japanese individuals aged 60 and older without dementia.
Measurements: Self‐reported daily sleep duration was grouped into 5 categories (<5.0, 5.0–6.9, 7.0–7.9, 8.0–9.9, ≥10.0 hours). The association between daily sleep duration and risk of dementia and death was determined using a Cox proportional hazards models.
Results: During follow‐up, 294 participants developed dementia, and 282 died. Age‐ and sex‐adjusted incidence rates of dementia and all‐cause mortality were significantly greater in subjects with daily sleep duration of less than 5.0 hours and 10.0 hours and more than in those with daily sleep duration of 5.0 to 6.9 hours. These associations remained unchanged after adjustment for potential confounding factors (<5.0 hours: hazard ratio (HR)=2.64, 95% confidence interval (CI)=1.38–5.05 for dementia; HR=2.29, 95% CI=1.15–4.56 for death; ≥10.0 hours: HR=2.23, 95% CI=1.42–3.49 for dementia; HR=1.67, 95% CI=1.07–2.60 for death). Similar U‐shaped associations were observed for Alzheimer's disease and vascular dementia. With regard to the influence of hypnotic use on risk of dementia and death, subjects who used hypnotics and had any sleep duration had a risk of dementia that was 1.66 times as great and a risk of death that was 1.83 times as great as those who did not use hypnotics and had a daily sleep duration of 5.0 to 6.9 hours.
Conclusion: Short and long daily sleep duration and hypnotic use are risk factors for dementia and death in Japanese elderly adults.

Authors
Tomoyuki Ohara, Takanori Honda, Jun Hata, Daigo Yoshida, Naoko Mukai, Yoichiro Hirakawa, Mao Shibata, Hiro Kishimoto, Takanari Kitazono, Shigenobu Kanba, Toshiharu Ninomiya

[link url="https://www.sciencedaily.com/releases/2018/06/180606082309.htm"]Wiley material[/link]
[link url="https://onlinelibrary.wiley.com/doi/abs/10.1111/jgs.15446"]Journal of the American Geriatrics Society abstract[/link]

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