Difficulties in initiating or maintaining sleep at middle-age are associated with an increased risk of dementia, according to a new study. The 20-year follow-up study was conducted among 2,682 men participating the Kuopio Ischaemic Heart Disease Study. Shorter or longer sleep than 7–7.5 hours related independently with an increased risk of lung cancer after health behavior, such as smoking, was taken account of. Additionally, a relationship between higher serum copper levels and short sleep duration was observed.