Table 4.

Association between sleep duration and levels of male reproduction hormone stratified by reporting to being often tired or not.

	(n = 2095)	Effect of sleep duration on hormone levels stratified by tiredness/β (95% CI)
		Yes, I am often tired (n = 331)	No, I am not often tired (n = 1764)	P value for interaction
Free testosterone (pmol/L)	<7 h of sleep	−28.4 (−53.8; −3.0)	7.7 (−3.4; 18.9)
	7–9 h of sleep	0 (reference)	0 (reference)
	>9 h of sleep	−48.1 (−79.0; −17.2)	−34.9 (−63.3; −6.6)	P = 0.037
Bioavailable testosterone (nmol/L)	<7 h of sleep	−0.7 (−1.3; −0.1)	0.2 (−0.1; 0.5)
	7–9 h of sleep	0 (reference)	0 (reference)
	>9 h of sleep	−1.1 (−1.9; −0.2)	−0.8 (−1.5; −0.1)	P = 0.049
Total testosterone (nmol/L)	<7 h of sleep	−1.8 (−3.2; −0.5)	0.7 (0.1; 1.3)
	7–9 h of sleep	0 (reference)	0 (reference)
	>9 h of sleep	−3.0 (−4.9; −1.1)	−0.7 (−2.3; 0.8)	P = 0.004
SHBG (nmol/L)	<7 h of sleep	−2.8 (−5.9; 0.2)	1.8 (0.5; 3.2)
	7–9 h of sleep	0 (reference)	0 (reference)
	>9 h of sleep	−5.6 (−9.9; −1.3)	3.9 (0.4; 7.3)	P < 0.001
DHEAS (nmol/L)	<7 h of sleep	−0.2 (−0.4; 0.0)	−0.0 (−0.4; 0.1)
	7–9 h of sleep	0 (reference)	0 (reference)
	>9 h of sleep	−0.0 (−0.3; 0.2)	−0.2 (−0.4; 0.0)	P = 0.143

Results from multivariable linear regression analyses of male serum reproductive hormones, SHBG and DHEAS among Danish men according to self-reported hours of sleep per day and whether or not they often feel very tired in their everyday life. Adjusted for age, smoking, BMI, alcohol intake and physical activity.

DHEAS, dehydroepiandrosterone-sulfate; SHBG, sex hormone-binding globulin.