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, according to a study.

The research, published in the Journal of the American Heart Association, focused on two measures of brain health: Matter hyper intensities (WMH), which are lesions on the brain indicating brain ageing, and fractional anisotropy, which measures the uniformity of water diffusion along nerve axons.