Getting either too much or too little sleep is associated with changes in the brain that have been shown to increase the risk of stroke and dementia later in life, a new Yale School of Medicine study finds.
In one of the largest neuroimaging studies of its kind to date, the Yale team examined brain images of close to 40,000 healthy, middle-aged participants to evaluate how sleeping habits might impact two measures of brain health: white matter hyperintensities (WMH), which are lesions on the brain indicating brain aging, and fractional anisotropy, which measures the uniformity of water diffusion along nerve axons. More WMH, larger WMH, and lower fractional anisotropy are associated with increased risk of stroke and dementia.
Researchers found compared with optimal sleep (7-9 hours per night), participants with short sleep had higher risk of WMH presence, larger WMH volume where WMH was present, and lower fractional anisotropy. Long sleep (averaging more than 9 hours per night) was associated with lower fractional anisotropy and with larger WMH volume, but not with risk of WMH presence.
