Better sleep helps you stay sharp at work, play with the grandkids, and, new research shows, prevent dementia, reports philly.com.

Penn Medicine physician Nalaka Gooneratne says research shows that older adults need the least sleep of any age bracket.

The recommended night’s sleep decreases as we age: eight to 10 hours for teenagers; seven to nine hours for young and middle-aged adults; and seven to eight hours starting at age 65.