July 22, 2015

Too Much Sleep May Be Linked to Type 2 Diabetes

I almost passed this by when I read the title - Longer Sleep Duration Linked to Type 2 Diabetes. I thought this must be a joke or a very poor study. When I read the article, I admit that it is worse than most studies and has some obvious weaknesses. Italics are my thoughts.
  1. An increased risk for developing type 2 diabetes was observed in participants slept for an average of less than 5.5 per night or more than 9 hours per night. I thought this was about too much sleep and they talk about five and one half hours per night.
  1. BMI and weight changes may serve as confounding factors affecting the results of the study. They did not keep track of this during the trial to the extent they should have.
  1. Sleep and diabetes are often affecting each other. Normally we hear about this after a person has type 2 diabetes when lack of sleep makes type 2 diabetes more difficult to manage.
People who sleep 9 or more hours per night are associated with higher risk of incident diabetes according the study. Evidence suggests that diabetes and sleep problems are linked to each other. Diabetes can cause insomnia in some people and sleep deprivation may increase for developing diabetes. Yes, “may” is the operative word. Someone blew this, if you have diabetes, how do you develop diabetes?

This was a 20-year study that consisted of four periods of five years each. I would have thought they could have done a more thorough job of research instead of saying, “Further studies are recommended before the association between sleep and diabetes can be established.”

The researchers recorded and calculated the changes in sleep duration for a total of 17,841 participants without diabetes. At the end of each period, incident diabetes was defined using 1) fasting glucose, 2) 75-g oral glucose tolerance test, and 3) glycated hemoglobin, in conjunction with diabetes medication and self-reported doctor diagnosis.

When compared to the controlled group of persistent 7 hours sleepers, results of the study showed "an increase of greater than or equal to 2 hours of sleep per night was associated with a higher risk of incident diabetes in analyses adjusted for age, sex, employment grade, and ethnic group. This association was partially weakened by adjustment for BMI and change in weight. An increased risk of incident diabetes was also seen in persistent short sleepers (average of less than or equal to 5.5 hours of sleep per night).

According to the study, the significance of the results was weakened when researchers factored in adjustment for BMI and changes in the weight. The authors suggest that, "greater weight and weight gain in this group partly explain the association."

The findings of this study provides some understanding about the role of sleep and its effect on the development of diabetes. I am still disappointed by the study.

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