The better the quality of your sleep, the longer you'll live. Researchers at the University of Pittsburgh came to this conclusion after doing a study in which they followed 184 healthy men and women aged 58-91 for an average of 13 years.
Inventions such as artificial light, TV and the internet mean we sleep less long, and the quality of our sleep is probably also worse. As a result our health is suffering, sleep researchers suspect.
They base their reasoning on studies which have shown that too little sleep reduces the body's maximal oxygen uptake, stimulates overweight and lowers testosterone levels. And that's just a few of the problems associated with lack of sleep.
When the researchers compared the over-sixties in the study who had died with the over-sixties who were still alive, they discovered three sleep factors that reduced the chance of dying.
Among the survivors, there were significantly more subjects who, after getting into bed, took less than half an hour to fall asleep. Secondly, the survivors lay awake less often and they slept for over 80 percent of the time that they lay in bed. And finally, the survivors spent more time in deep sleep.
When you get up in the morning you can tell whether you have slept deeply. You aren't properly awake for the first half hour, but after that you feel well rested.
The researchers then repeated their experiments with rats whose front paw had been broken. Half of the animals were given nothing; the other half were given an injection of the anabolic phyto-hormones in Cissus quadrangularis, every other day. The figure below shows that the extract helped the rats' bones to strengthen more quickly.
The most important predictor of death that the researchers found was the amount of time it took the subjects to fall asleep. If this was longer than 30 minutes, their chance of dying was higher by a factor of 2.14.
For the subjects who spent more than 80 percent of their time in bed awake, their chance of dying was greater by a factor of 1.93. If they noticeably frequently or infrequently entered REM sleep phases, the chance of dying was greater by a factor of 1.71.
"The fact that certain sleep parameters independently predicted cumulative probability of death may have practical implications for sleep-related interventions in older adults", the researchers write. "In particular, one could hypothesize that interventions that optimize and/or protect sleep initiation and sleep quality in old age might not only add quality to life but prolong life as well."