Over 65s who have difficulty getting back to sleep when they wake up in the night are less likely to develop dementia than those who find it hard to nod off in the first place, a new study suggests. Researchers in the US monitored a sample of dementia free over-65s during a ten year period. They found those who had frequent difficulty falling asleep within 30 minutes of turning off the lights – or used sleep medication – had an increased risk of developing the disease. It’s unclear, they say, why those with disrupted sleep were at less risk , but hope further research will offer clues.