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The risk of dementia increases by 30 percent among people who sleep fewer than six hours a night in their 50s and 60s, research findings show. (Getty Images Bank)

The risk of dementia increases by 30 percent among people who sleep fewer than six hours a night in their 50s and 60s, research findings show.

A joint University of Paris and University College London research team published findings in the scientific journal Nature Communications from a study in which 8,000 British participants were tracked over a period of 30 years.

A comparison of one group of participants in their 50s and 60s that slept fewer than six hours a night and another that slept for seven hours a night showed the former group to be at a risk 1.3 times greater for dementia than the latter.

According to the research team, no causal relationship was established between sleeping habits and dementia, but the long-term tracking study showed a significant correlation.

The joint French and British research team analyzed correlations between sleep times and dementia for participants in their 50s, 60s and 70s in the Whitehall II cohort study, which has been taking place for 30 years.

The Whitehall study is a long-term research project studying British government employees to investigate socioeconomic inequalities related to health.

Among the 10,308 participants in the Whitehall II study, the research team analyzed 7,959 for whom data on sleep times were available. Of this group, 521 participants developed dementia, with the majority receiving their diagnosis after the age of 70.

The 6,875 surviving participants who had not developed dementia by the age of 70 were separated into three groups that had continuously maintained sleep times of six or fewer hours, seven hours, and eight hours and three groups that had altered their sleep habits midway through the study. The analysis showed a dementia risk 1.3 times higher in the group that slept continuously for six or fewer hours a night compared with the group that continuously maintained sleep times of seven hours.

According to the research team, no correlation was observed between dementia and long sleep times of eight or more hours. There was also no reported correlation with sociodemographic, behavioral, cardiometabolic or mental health factors.

“Depression and mood disorders in general are related to changes in sleep and thought to play an important part in the association of sleep duration with dementia,” the team wrote.

“In the present study, adjustment for depressive symptoms and central nervous system drugs, as well as analysis undertaken among those without a history of mental disorders did not show mental health to explain the association,” it explained.

By Lee Keun-young, senior staff writer

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