Older adults who sleep nine or more hours a day may be at higher risk of developing dementia than those who sleep eight hours.  Julian Benito-Leon, from University Hospital '12 de Octubre’ (Spain), and colleagues studied 3,286 men and women, ages 65+, for of period of 3.2 years.  The researchers surveyed sleep habits of all subjects and diagnosed dementia onset in 140 participants during the study period. Among those subjects who reported sleeping 9+ hours a day, 5% developed dementia, compared to 2% of those who slept for 7 hours daily and 4% of those who slept 8 hours each day.  The researchers conclude that: “Prolonged sleep duration (night-time sleep and daytime napping) may be associated with an increased risk of dementia.”