If young children do not get their recommended daily sleep, their risk of becoming overweight is significantly greater, researchers from New Zealand reported in the BMJ (British Medical Journal). Even after certain lifestyle factors were taken into account, the lack of sleep and overweight link was still there, the authors added.
Previous studies had shown an association between lack of sleep and increased bodyweight in children, the authors explained. However, doctors are not certain what it is in sleep deprivation that might cause this effect.
The researchers gathered data on 244 kids from The Family Lifestyle, Activity, Movement and Eating (FLAME) study in Dunedin, New Zealand. Their aim was to determine whether lack of sleep was linked to differences in body composition and to measure the risk of becoming overweight (in children).
Every six months, the BMI (body mass index) and body composition of each child was measured and recorded from the age of 3 to 7 years. Each child wore a belt which carried a device that monitored body movement, this enabled the researchers to record their sleeping habits. A dietary questionnaire was also completed when they were 3, 4 and 5 years old.
The investigators also gathered data on other factors which can impact on body weight of children, such as their birth weight, their mother’s education, mother’s income, mother’s BMI, whether the mother smoked during pregnancy, and her ethnicity. The children slept an average of 11 hours per day.
The children who slept the least had a considerably greater chance of being overweight by the time they were 7, even after taking into account the other risk factors. For each extra hour’s sleep each night, the researchers worked out that their BMI would be 0.49 lower, as well as having a 61% lower risk of being overweight/obese by 7 years of age. For a child of average height, this is equivalent to a 0.7kg difference in weight. This may seem like a small amount, but in public health terms, and when applied throughout a whole population, the benefits are considerable.
The authors add that the BMI reductions were due to less fat mass rather than lean-tissue mass. This shows that lack of sleep has a detrimental effect on body composition.
The researchers believe that when a child does not get enough sleep, his/her dietary intake is affected as well as energy expenditure, resulting in less physical activity.
The authors conclude that sleep plays an important role in the future body composition of young children. As a public health measure, healthy sleeping habits should be encouraged. They also believe that further studies are required on the impact of more sleep on children’s health.
Professor Francesco Cappuccio and Associate Professor Michelle Miller from the University of Warwick say that not only may long-term sleep deprivation directly contribute towards overweight/obesity in children, but there may also be other health consequences.
We need further studies to determine what behavioral methods can be used to prolong children’s (and adult’s) sleep duration. They add that it might be a good idea to tell people of all ages now that long-term sleep deprivation might contribute to ill-health in children (and adults).
Written by Christian Nordqvist