(HONOLULU, HAWAII, OCTOBER 24, 2011) -- Sleeping less than 8 hours a night may be linked to weight gain in teens, according to new survey results presented at CHEST 2011. Furthermore, obesity was linked to short sleep duration in teen males, with the fewest hours slept linked to the highest BMI levels.
"Sleep is food for the brain. When teens do not get enough sleep, they fall asleep in class, struggle to concentrate, look and feel stressed, get sick more often, and do not meet their obligations due to tiredness," said study author Lata Casturi, MA, RPSGT, Baylor College of Medicine Sleep Center in Houston, TX. "Teens who sleep fewer than eight hours may also consume more calories than those who sleep more than eight hours. Therefore, they have a higher risk for obesity and associated health problems, including high blood pressure, heart disease, and stroke."
Casturi and colleagues, including coauthor Anita Rao (presently a 10th grader at Dawson High School in Pearland, TX) surveyed 255 teens - 108 males and 147 females - in high school to obtain self-reported measures of height and weight (used for BMI calculation) and both weekday and weekend quantity of sleep. Among males, results indicated the average sleep time on weekdays was 6 hours 32 minutes and on weekends 9 hours 10 minutes. Among females, the average weekday sleep time was 6 hours 30 minutes and the average weekend sleep duration was 9 hours 22 minutes. Teen males who slept 7 hours or less on weekdays had an average BMI that was 3.8 percent higher than those who slept more than 7 hours. Likewise, teen females who slept 7 hours or less had a BMI that was 4.7 percent higher than females who got more than 7 hours of sleep per weekday.
But how does lack of sleep really affect weight gain? According to researchers, hormones leptin and ghrelin work in a "checks and balances" system to control feelings of hunger and fullness. Ghrelin, which is produced in the gastrointestinal tract, stimulates appetite, while leptin, produced in fat cells, sends a signal to the brain when you are full. "When you don't get enough sleep, it drives leptin levels down, which means you don't feel as satisfied after you eat. Lack of sleep also causes ghrelin levels to rise, which means your appetite is stimulated, so you want more food," said co-author Radha Rao, MD, DeBakey VA Medical Center, Houston, TX. "The two combined, can set the stage for overeating, which in turn may lead to weight gain."
Furthermore, after adjusting for potential cofounders, short sleep duration (<8 hours) was associated with obesity in male teens. A negative correlation also was found between weekday sleep duration and obesity in males, with the fewest hours of weekday sleep associated with the highest BMI. There was no evident correlation between obesity and weekday sleep hours in teen females.
The researchers believe the sex-related difference in sleep and weight gain may be due to the differences in body composition during puberty. "Males and females experience differential growth rates and hormone secretion during puberty. The sleep factors that impact metabolism may increase weight gain differently in the two sexes," explained Ms. Casturi.
In addition to weight gain, lack of sleep during teenage years can result in poor sleep habits that continue into adulthood and result in long-term health consequences.
"Sleep promotes growth in children and adolescents and strengthens the immune and nervous systems. Hence, sleep deprivation early in life may cause the youngsters to suffer from a lifetime of irreversible higher health risks," said Anita Rao. Researchers recommend that parents educate teens about good sleep habits early in life, which include setting a regular sleep schedule, turning off technological devices at night, and avoiding caffeine and exercise at bedtime.
"Sleep deprivation can have an immediate impact on our physical performance and cognitive function, but can also lead to long term health problems, including cardiovascular and respiratory conditions," said Suhail Raoof, MBBS, FCCP, President of the American College of Chest Physicians. "Developing good sleep habits in adolescence may help to reduce the risk of related health conditions later in life."