The older people had a harder time falling to sleep and slept shorter hours.
Scientists say it could be because older people don't expend as much energy as younger adults and they tend to nap, which could be why healthy adults sleep less in their 60's than they did in their 20's.
If true, researchers say the observation could mean that what many elderly people interpret as insomnia could be a completely normal reflection of an age related shift in their internal clock.
