Sleep Arithmetic can Subtract Years From Your Life

Too much or too little sleep can lower brain function and speed aging

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) If the number of hours you sleep don't add up, you could be subtracting years from your life and lowering brain function in the process. Bottom line - you need 6-8 hours of sleep - not more, not less.

Changes in sleep that occur over a five-year period in late middle age can affect cognitive function (thought processes, memory, verbal skills) in later life.

A new study suggests that women and men who begin sleeping more or less than 6 to 8 hours a night are more likely to speed up cognitive decline that's equal to four to seven years of aging.

"Get 6-8 hours of sleep each day."

This study, published in the May 2011 journal Sleep, found that women who sleep 7 hours scored the best on cognitive tests, closely followed by those who sleep six hours. For men, test scores dropped when they slept less than 6 hours or longer than 8 hours.

Habitual sleep duration was measured at baseline and follow-up using a single question: "How many hours of sleep do you have on an average week night?"

"The detrimental effects of too much, too little and poor quality sleep on various aspects of health have begun to receive more attention," said lead author Jane Ferrie, PhD, senior research fellow in the University College London Medical School.

"Given that our 24/7 society increasingly impinges on the lives of many people, it is important to consider what effects changes in sleep duration may have on health and well-being in the long term," she added.

The Study

  • Used data for 5,431 participants (1,459 women and 3,972 men) from Phase 5 (1997-1999) and Phase 7 (2003-2004) of the Whitehall II study, which included more than 10,000 London-based office staff aged 35-55 in 1985
  • Participants were divided into four groups based on the change in sleep duration between the two checkpoints
  • Groups were compared with reference groups who reported no change in sleep duration
  • Those who began and continued sleeping more or less than 6-8 hours a day over a five-year period scored lower on cognitive tests
Reviewed by: 
Review Date: 
May 3, 2011
Last Updated:
May 4, 2011