Poor Sleep Quality Linked to Increased Glucose Levels

Pauline Anderson

May 17, 2011

May 17, 2011 — Poor sleep quality, including insomnia, is associated with higher levels of blood glucose, insulin, and insulin resistance in patients with type 2 diabetes, a new study shows.

"The strength of these associations suggests that the diagnosis and therapeutic treatment of type 2 diabetes should take into account the possible existence of sleep disturbances," the study authors, led by Kristen L. Knutson, PhD, from the Department of Medicine, University of Chicago, Illinois, write.

"If improving sleep can help improve glucose control in people with diabetes, then a potentially new therapeutic intervention may be identified."

The study appears in the May issue of Diabetes Care.

CARDIA Study

The goal of the study was to examine whether sleep duration or quality, measured using wrist actigraphy, is associated with levels of fasting glucose, fasting insulin, or estimated insulin resistance in a community-based sample of early to middle-aged adults.

The study is ancillary to a large ongoing cohort study, the Coronary Artery Risk Development in Young Adults (CARDIA) study, being performed at 4 sites in the United States.

In 2003-2005, researchers collected sleep measures using questionnaires and wrist actigraphy for 531 subjects without diabetes and 40 with diabetes. Subjects were considered to have diabetes if they had a fasting plasma glucose level of at least 6.99 mmo/L, had received a diagnosis of diabetes, or were taking medications for diabetes.

Subjects wore a wrist monitor that counts the number of wrist movements for 3 days on 2 occasions about 1 year apart between 2003 and 2005. Researchers used special software to calculate sleep duration and fragmentation gathered by the monitors.

Insomnia was defined as average sleep efficiency of less than 80% based on actigraphy plus self-reported difficulty falling asleep or waking up 3 or more times per week.

Before glucose and insulin were measured, patients fasted for 12 hours. Insulin resistance was estimated from the homeostatic model assessment (HOMA).

After adjustments, the study found that a 10% higher sleep fragmentation in patients with diabetes was associated with a higher fasting glucose level, a higher fasting insulin level, and a higher HOMA level. These increases were even further magnified for those with insomnia.

Table. Percent Increase in Glucose, Fasting Insulin, and HOMA Associated With Each 10% Increase in Sleep Fragmentation and Insomnia

Measure Sleep Fragmentation (Per 10% Increase) Insomnia
Fasting glucose, % 9 23
Fasting Insulin, % 30 48
HOMA, % 43 82

HOMA = homeostatic model assessment

"It is possible that the effects of sleep disturbances are more pronounced in subjects with diabetes because the mechanisms responsible for glucose homeostasis are already deficient and therefore more vulnerable," write the study authors.

Frequent snoring, which could be an indicator of sleep-disordered breathing, was associated with higher levels of fasting glucose, insulin, and insulin resistance in patients without diabetes in unadjusted models only, which suggests that body mass index may play a role, said the study authors.

A limitation of the study was that it did not allow for determination of causality; although evidence supports the concept that disturbed sleep impairs glucose metabolism, poorly controlled glucose levels may also impair sleep.

The study authors give examples to illustrate the effects of sleep they have seen on blood glucose.

"To translate these statistical associations, let us consider a diabetic patient who has good sleep quality with sleep fragmentation of only 5% and who has a fasting glucose level of 7.8 mmol/L," they write. "Let us consider a second diabetic patient with identical demographics but a sleep fragmentation of 15%, which is the clinical threshold for insomnia. His or her average fasting glucose level is estimated to be 0.7 mmol/L higher than the first patient."

Similarly, if 2 patients differ only in the presence of insomnia and the one without insomnia had a fasting glucose level of 7.8 mmol/L, they point out, "the average fasting glucose level in the patient with insomnia would be 1.6 mmol/L higher."

The study authors have disclosed no relevant financial relationships.

Diabetes Care. 2011;34:1171-1176. Abstract

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