High Testosterone Predicts Sleep in Obese Men

High testosterone levels predict more shallow sleep in overweight and obese men, independently of obstructive sleep apnea (OSA), according to a new study.

“This finding could have clinical relevance in the context of the recent increase in testosterone prescriptions in middle-aged men, as poor sleep quality has been linked to increased risk of diabetes and hypertension,” said senior author Eve Van Cauter, PhD, Director of the University of Chicago Sleep, Metabolism and Health Center.

About three-fourths of American men are now considered overweight or obese. The researchers aimed to identify predictors of slow-wave activity during sleep in overweight and obese men.

Slow-wave activity in the brain during non–rapid eye movement sleep is a marker of sleep depth, and stable activity has been implicated in the control of glucose homeostasis and blood pressure. Low slow-wave activity indicates shallow sleep, which causes a person to wake up easily and feel unrested after a night of sleep. Studies exploring the predictors of the large inter-individual differences in slow-wave activity have been performed mainly in lean persons, reported Lisa L. Morselli, MD, PhD, Research Project Professional at the University of Chicago sleep center.

The researchers recruited 44 men, average age 35 years, who were overweight or obese for an overnight in-laboratory polysomnogram. Total plasma testosterone was measured on the morning after the polysomnogram. All of the men were otherwise healthy and were nonsmokers.

The men’s selection for the study did not consider whether they had symptoms or a history of OSA, said Dr Van Cauter. However, the sleep study showed that two-thirds of the men did have OSA, which in most cases was moderately severe. The median apnea-hypopnea index (AHI) was 16 events per hour.

To explore the factors associated with slow-wave activity, the researchers performed statistical analyses using multivariate regression that first included only the men’s demographic characteristics. They found that older age and African-American race predicted low slow-wave activity, or shallow sleep. Body mass index had no significant effect on slow-wave activity.

Later analyses showed that higher total testosterone levels strongly correlated with more shallow sleep. This association was independent from the presence of other factors known to decrease sleep quality, such as age, race/ethnicity, and OSA severity, Dr Van Cauter said. “The negative association of total testosterone and race with non–rapid eye movement slow-wave activity persisted, whereas AHI and age only weakly predicted slow-wave activity,” reported Dr. Morselli.

She concluded that “in overweight and obese men under 50 years old, non–rapid eye movement slow-wave activity is negatively predicted by total circulating testosterone levels, in addition to race, age, and AHI. These results have potential clinical implications as exogenous testosterone is being increasingly prescribed to middle-aged men.”

Further studies are needed to clarify the impact of testosterone replacement on sleep quality, especially sleep depth, the researchers said.

The researchers presented the results on June 23, 2014 at the 16th International Congress of Endocrinology and the Endocrine Society’s 96th Annual Meeting and Expo in Chicago.