Service members diagnosed with chronic insomnia may face increased risk of type II diabetes, high blood pressure

Service members with chronic insomnia were at higher risk for type II diabetes with a hazard ratio of 2.17 and for hypertension (hazard ratio of 2.00) when the data were adjusted for age, race, obesity and gender compared to a cohort of service members who had not been diagnosed with insomnia, according to the report released in the October issue of the Medical Surveillance Monthly Report (MSMR) published by the Armed Forces Health Surveillance Center (AFHSC).

The retrospective cohort study identified groups of service members in the active components of the Army, Navy, Air Force, Marine Corps and Coast Guard during a surveillance period between January 1, 1998 and December 31, 2013. For the study, the incidence of diabetes and hypertension among approximately 100,000 incident cases of chronic insomnia was compared with their incidence in a control group of an equal number of individuals without insomnia.

Insomnia is a common complaint among service members due to career-related stress factors, such as frequent deployments with demanding military operations, varying work shifts, and the challenges of maintaining relationships with their spouses and families.

"This type of analysis has military relevance because it supports the notion that adequate sleep among our service members is important not only for accident prevention and work performance, but also for additional long-term health benefits," said Air Force Lieutenant Colonel Paul E. Lewis, the author of the study and a preventive medicine resident at the Uniformed Services University of the Health Sciences.

During the 16-year surveillance period, a total of 205,740 incident cases of chronic insomnia were diagnosed among active component service members. The highest annual overall rate was in 2012 with 252.3 cases per 10,000 person-years. After years of steady increase, the rate leveled out in 2013 at 248 cases per 10,000 person-years. Since 2005, the Army has consistently had the highest rate of chronic insomnia among the services, peaking at 432.8 cases per 10,000 person-years in 2012. This rate was more than 2.5 times the rate of any of the other services that same year.

The risk of type II diabetes in the insomnia cohort, compared to those without insomnia, was elevated in all race categories and in those with and without diagnoses of obesity (Table 4). Service members in the insomnia cohort were more likely to be black, non-Hispanic (18.9 percent) or obese (12.4 percent) than those in the control cohort (16.6 percent and 5.9 percent, respectively).

The association of chronic insomnia with hypertension was seen both in service members younger than 30 years of age and in those aged 30 years or older, with adjusted hazard ratios of 2.32 and 1.94, respectively. By gender, chronic insomnia had a stronger association with hypertension in men (adjusted hazard ratio of 2.17) than in women (adjusted hazard ratio of 1.59).

The adjusted hazard ratio was also greater for white, non-Hispanics (ratio of 2.26) than for black, non-Hispanics (ratio of 1.72). Both obese subjects and non-obese subjects had significantly increased risks of hypertension related to insomnia, with adjusted hazard ratios of 2.09 and 1.86, respectively.

Previous studies on this topic have provided conflicting results, with some demonstrating a strong association and others finding minimal to no association. There are several reasons why the findings of this study may not be directly comparable to studies in civilian populations. Military members are generally younger and have less co-morbidity than their civilian counterparts.

This analysis employed a longitudinal study design that allowed for follow-up of individuals over time, whereas many previous study designs did not allow evaluation between an exposure to a risk factor and a subsequent outcome. The average follow-up time was 3.09 years in the insomnia cohort and 3.42 years in the control cohort. These differences in methodology might partially explain the observed increased risks of hypertension and diabetes associated with chronic insomnia in this study but not seen in some other studies.

The report can be found at: http://www.afhsc.mil/documents/pubs/msmrs/2014/v21_n10.pdf#Page=6