New study reveals more about how sleep affects type 2 diabetes risk

by Barbara Hewitt on November 3, 2015

It is known that too much sleep or too little sleep increases the risk of developing type 2 diabetes in middle age, but not much has been known about the long term changes.

Now, a study of almost 60,000 women in the United States has found that a chronic short sleep duration of six hours or less or increasing average sleeping time by two hours or more over a period of several years increases the risk.

Sleep-StudyThe researchers from the Harvard TH Chan School of Public Health and Kaiser Permanente Division of Research in California found an extra two hours or more increased the risk of developing type 2 diabetes by 15%, even factoring in variations in diet, physical activity, snoring, sleep apnoea, depression and body-mass index.

Change in sleep duration was recorded as the difference between self-reported 24 hour sleep duration in 1986 and 2000. Diet, physical activity and covariates were updated every two to four years and self-reported diabetes was confirmed via validated questionnaires. Computer modelling was then used to evaluate the changes in relative risk of diabetes related to increases and decreases in sleep.

The researchers found that chronically sleeping six hours or less per day as well as increases in sleep duration of more than two hours per day were associated with modest increased risk of developing type 2 diabetes.

However, after adjustment for body-mass index, associations of chronic short sleep duration with diabetes became non-significant, while associations of increases in sleep duration with diabetes persisted.

Notably, women who increased their sleep duration were more likely to have been short sleepers to begin with, suggesting that the adverse influence of short sleep duration in mid- life may not be compensated for by later increases in sleep duration.

A number of potential causes for the authors’ findings are discussed in the paper, including that increases in sleep duration can both result from or induce an inflammatory state. For example, proinflammatory cytokines in the blood, abundant in obesity, can induce sleepiness, and a recent experiment extending time in bed increased inflammation and worsened mood among healthy volunteers.

“Chronic short sleep duration and increases in sleep duration are associated with increased risk of diabetes. Decreases in sleep duration have modest, adverse associations with diet quality and physical activity, while increases in sleep duration have modest, adverse associations with weight gain,” the scientific report concludes,

Lead researcher Dr Elizabeth Cespedes said that ongoing trials will provide further insight as to whether changes in sleep duration influence energy balance.


The opinions expressed in this article do not necessarily reflect the views of the DiabetesForum.com Community and should not be interpreted as medical advice. Please see your doctor before making any changes to your diabetes management plan.

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