Monday, September 6, 2010

Sleep, Diet and Life Expectancy

Sleep seems to be on the mind of lots of scientists over the last few days with a number of intriguing sets of results being published.

According to a study published on Tuesday in PLoS Biology, when flies are starved they are able to stay awake for long periods of time without feeling the downsides of going without a nap.

The experiment was conducted by starving some flies while allowing others to feed normally and then providing a physical jolt to prevent them from nodding off. The starved flies were less susceptible to the effects of sleep deprivation such as cognitive impairment.

The scientists also made use of mutant fruit flies which lack the 'canonical clock gene cycle'. Such flies normally die within 10 hours of being deprived of sleep, but when starved they lasted nearly three times as long.

The authors believe that two genes recently shown to control the response to starvation in fruit flies brummer (bmm) and Lipid storage droplet 2 (Lsd2) also have a role to play in sleep regulation.

"brummer mutants, which are fat, show exaggerated response to sleep loss. In contrast, mutants for Lipid storage droplet 2 are lean and are able to stay awake without becoming sleepy or showing signs of cognitive impairment" the authors write.

"Given that metabolic pathways are highly conserved between mammals and flies, it will be interesting to determine whether lipid [fat] metabolism also plays a similar role in mammals".

Meanwhile, a recent study reported in the September 1st issue of Sleep found that men with serious sleep problems had much higher mortality rates.

The study of 1,742 men and women, who were randomly sampled in Pennsylvania and studied for 14 and 10 years respectively found that the overall mortality rate was 21% for men and 5% for women.

'in men who experienced insomnia, that mortality rate was significantly increased' However, in men who experienced insomnia (who slept for less than 6 hours a night), that mortality rate was significantly increased. In women, on the other hand, mortality was not found to be associated with insomnia and disrupted sleep.

Of the men who were studied, 51% of insomniacs died during the study period, compared to just 9% of normal sleepers.

“Insomnia has potentially very severe side effects,” said study co-author  Edward Bixler. “It needs to be treated, and more effort needs to be put into sorting out better treatments.”

More evidence of sleepless nights being bad for your health came from a report also published on Wednesday (Sept. 1st) in which US researchers found that teenagers who sleep for less than 8 hours a night during Monday to Friday eat more snacks and fatty foods then those who get a solid eight hours.

The study analysed 240 teenagers and asked them to wear wrist monitors that measured sleep duration. During the study period, researchers discussed eating habits with the participants twice a day to monitor their food intake.

'teens who did not sleep well consumed 2.2% more calories from fat' The results, also published in the September issue of Sleep, showed that teens who did not sleep well consumed 2.2% more calories from fat compared to those who slept for eight hours. Girls were more prone to this than boys; consuming 3.3.% more calories from fat compared to 0.9% in boys.

Teenagers who slept for eight hours or more a day during the working week consumed 1,723 calories per day, with 1,968 calories being consumed by those who  slept for less than eight hours.

The authors of this study have suggested that sleep may be the "missing link" in the fight against obesity, which up to now has focused on diet and exercise.

From this handful of recent studies it seems that diet and sleep are certainly closely linked and that more research is required to find out exactly the nature of that link.

One thing is for sure, if the results of the the mortality study is anything to go by, the outcome of cutting back on sleep time (either by choice or not) can be serious effects on your health and life expectancy.

Thimgan MS, Suzuki Y, Seugnet L, Gottschalk L, & Shaw PJ (2010). The perilipin homologue, lipid storage droplet 2, regulates sleep homeostasis and prevents learning impairments following sleep loss. PLoS biology, 8 (8) PMID: 20824166

Vgontzas AN; Liao D; Pejovic S; Calhoun S; Karataraki M; Basta M; Fernández-Mendoza J; Bixler EO (2010). Insomnia with short sleep duration and mortality: the Penn State Cohort SLEEP, 33 (9), 1159-1164

Weiss A; Xu F; Storfer-Isser A; Thomas A; Ievers-Landis CE; Redline S (2010). The association of sleep duration with adolescents’ fat and carbohydrate consumption SLEEP, 33 (9), 1201-1209


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