1. Sleep quality but not duration is associated with testosterone levels: a pilot study of men from an urban fertility clinic
Linda G. Kahn1, Pam Factor-Litvak1, Mark V. Sauer2
1 Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY
2 Department of Obstetrics and Gynecology, College of Physicians & Surgeons, Columbia University, New York, NY
Introduction
Prior research suggests that poor sleep quality and short sleep duration are associated with reduced testosterone in men. Testosterone levels peak during the first REM cycle, approximately 3-4 hours after falling asleep, and remain elevated until awakening. Men with extreme sleep deprivation and those who do not attain deep sleep are vulnerable to low testosterone, which may increase their risk of clinical symptomatology and reduced fecundity. In this pilot study, we tested associations between sleep quantity/quality and serum testosterone.
Study protocol
Exposures
Sleep quantity: Average sleep per night (hours) was modeled as a continuous variable. Those who reported <6.5 hours of sleep/night were coded as having short sleep duration (SSD)
Sleep quality: Those who reported “very bad” sleep quality or use of any sleep medication within the past month were coded as having poor sleep quality (SQ)
Men (n=65) age years were recruited from the Center for Women’s Reproductive Care at Columbia University and given a self-administered survey that included questions about sleep quantity, sleep quality, and use of sleep medication. They subsequently had their weight and blood pressure taken, and provided a blood sample.
Methods
Study sample
Covariates
Potential covariates were identified based on theory and review of the literature. Each was entered individually into the crude models and variables were retained if they changed the estimated beta by more than 50% of the standard error. Age (continuous) and race (white vs. non-white) were also included in the final models.
Mean (SD)
Age
38.82 (5.93)
Percent
US born
Yes
57.38 No
42.62
Race
White
59.02
Black
6.56
Hispanic
24.59
Other
9.84
Education
< Bachelors degree
27.87
Bachelors degree
32.79
> Bachelors degree
39.34
Income
< $100,000
36.67
$ ,000
18.33
> $150,000 45
BMI
<25
26.23
>=25 to <30
44.26
>=30 to <35
16.39
>=35
13.11
Current smoking
93.44
Adjustedᵃ correlation between mean nightly sleep duration and serum testosterone level
Outcome
The outcome measure, serum testosterone (ng/dL), was log-transformed to normalize its distribution.
Statistical analyses
Linear regression was performed 1) unadjusted, 2) semi-adjusted for age, race, and current smoking (Y/N) in the sleep quantity models and age, race, current smoking, and income (<$100K vs. >=$100K) in the sleep quality models, and 3) fully adjusted for the above covariates plus body mass index (BMI, continuous).
Results and Conclusions
Average number of hours of sleep per night was positively but not significantly correlated with serum testosterone level.
SSD was negatively but not significantly associated with serum testosterone level.
Subjects with poor SQ had significantly lower serum testosterone levels in both unadjusted and adjusted models (β=-0.41, 95% CI [-0.64, -0.18]; βadj=-0.41, 95% CI [-0.65, -0.16]).
The relationship between poor SQ and testosterone was attenuated but still statistically significant when BMI was added to the adjusted model, βadj+BMI=-0.33, 95% CI [-0.58, -0.08], implying partial confounding by BMI.
Our study provides additional evidence for an association between poor SQ and reduced serum testosterone levels. These results suggest that sleep hygiene may be a valuable addition to the clinical management of men with low testosterone.
Ln Testosterone (ng/dL) vs. Short Sleep Duration
Unadjusted (n=60)
Adjusteda
(n=59)
Adjusteda+BMI (n=58)
beta
95% CI
SSD
(<6.5 hours
per night)
-0.11
-0.33, 0.10
-0.10
-0.31, 0.11
-0.08
-0.28, 0.12
Ln Testosterone (ng/dL) vs. Poor Sleep Quality
Adjustedb
(n=58)
Adjustedb+BMI (n=57)
Poor SQ ("very bad" or on meds)
-0.41
-0.64,
-0.18
-0.65,
-0.16
-0.33
-0.58,
ᵃ adjusted for age, race, current smoking status
ᵇ adjusted for age, race, current smoking status, income