Regularly sleeping six hours or fewer per night during middle age is associated with a greater risk of dementia, according to a new study of nearly 8,000 British adults followed over 25 years, published this week in Nature Communications. These findings cannot establish cause and effect, but suggest a link exists between sleep duration and dementia risk.
Nearly 10,000,000 new cases of dementia are reported worldwide every year. A common symptom is altered sleep; however, there is growing evidence to suggest sleep patterns before dementia onset may contribute to the disease. Time spent sleeping is linked to dementia risk in older adults (65 years and older), but it is unclear whether this association is also true for younger age groups.
Séverine Sabia and colleagues analysed survey data from UCL’s Whitehall II study that has examined the health of 7,959 British individuals since 1985. Participants self-reported their sleep duration, and some wore watch accelerometers overnight to confirm this was an accurate estimate. The study shows higher risk of dementia in those sleeping six or fewer hours per night at the age of 50 or 60. There was also a 30% increased dementia risk in those with consistently short sleeping patterns from middle to older age (from 50 to 70 years), irrespective of cardiometabolic or mental health issues (known risk factors for dementia).
The findings suggest sleep may be important for brain health in midlife. Future research may be able to establish whether improving sleep habits may help prevent dementia.