(CMR) A study has found middle-aged people who sleep six hours or less are more likely to develop dementia in their late 70s.
The research, published in the Nature Communications journal, followed approximately 8,000 people in Britain from they were 50 years old for about 25 years.
Participants reported how many hours they slept on an average weeknight in questionnaires between 1985 and 2016. Out of nearly 8,000 people, researchers found 521 had been diagnosed with dementia at an average age of 77.
It found that persons who consistently sleep six hours or less nightly were about 30 percent more likely than people who regularly got seven hours or more sleep to be diagnosed with dementia years later.
According to the research, “persistent short sleep duration at age 50, 60, and 70 compared to persistent normal sleep duration (7 hours or more) was associated with an increased dementia risk independently of sociodemographic, behavioral, cardiometabolic, and mental health factors. These findings suggest that short sleep duration in midlife is associated with an increased risk of late-onset dementia.”
The lowest dementia incidence per 1000 person-years was observed among those who slept 7 h per night, irrespective of the age at which sleep duration was measured.
A further key finding is that the association between short sleep duration and dementia is not attributable to mental health, the study stated.
It also found that depression and mood disorders, in general, are related to changes in sleep and were thought to play an important part in the association of sleep duration with dementia.
Previous studies associated dementia with long sleep hours; however, this study did not find any evidence to support that hypothesis.
“As in most previous studies, the number of long sleepers in our study was small and did not allow a robust estimation of the association with long sleep duration,” the study stated.