The Journal of Sleep Research analysis, which was led by researchers at the University of Cape Town, South Africa, included seven studies that aimed to increase sleep duration in adults by any sleep extension intervention. These studies had a combined number of 138 participants who were either healthy, healthy short-sleeping, overweight short-sleeping, or pre- or hypertensive short-sleeping individuals. The durations of the sleep extension interventions ranged from three days to six weeks and all successfully increased total sleep time by between 21 and 177 minutes.
Sleep extension was associated with improved measures of insulin sensitivity and reductions in overall appetite, desire for sweet and salty foods, intake of daily free sugar, and percentage of daily caloric intake from protein.
"Given the overwhelming evidence that sleeping less than seven hours is associated with an increased cardiometabolic risk, it is surprising that so few studies have explored whether extending sleep duration can lower cardiometabolic risk," said lead author Rob Henst, a PhD candidate. He noted that this review highlights the need for such studies and provides direction for future study designs.
"Although we have focused on studies with sleep extension interventions in this review, it is now apparent that poor sleep quality may be an equally important risk factor for cardiometabolic disease," added senior author Dr. Dale Rae. "Thus future studies testing interventions aimed at improving sleep quality are also required."