Obstructive Sleep Apnea Is Not an Independent Determinant of Plasma Testosterone

It is generally considered that obstructive sleep apnoea (OSA) lowers testosterone in men, although the data supporting this are relatively limited. We determined the relationship between the presence and severity of sleep disordered breathing and plasma testosterone in a comprehensively characterized community based cohort of men aged over 40yrs (MAILES) from whom fasting morning plasma samples were drawn in 2009-2010 (n=1869). Plasma total testosterone (T) was measured by liquid chromatography mass spectrometry (LCMS/MS). In 2011, home polysomnography was done in 810 randomly selected men from the cohort using an 8 channel Embletta X100 device. The Apnoea Hypopnea Index (AHI), and absence or presence and severity (mild: AHI 10-20; moderate AHI 21-30; severe: AHI ≥ 30) of OSA were classified according to the International Classification of Sleep Disorders (ICDS-2) from the American Academy of Sleep. After excluding men with pathological conditions or taking medications affecting testosterone, with missing values or using CPAP, 654 men aged 41-85 remained.

The effect of OSA severity, or AHI, on T were analysed using generalized linear models controlling for potential confounders (age, BMI, smoking, marital status, presence of depression (self-report), HbA1c and SHBG). The mean (±SD) characteristics of the men were: age 59 (10) yrs, T 16.5 (5.4) nmol/L, SHBG 33.1 (13.4) nmol/L, BMI 28.4 (4.2) kg/m2, AHI 14.1 (14). OSA was present in 53.7%, (mild 28.6%, moderate 13.6, and severe 11.5%). A significant inverse relationship between AHI and T (Beta -.118, P=0.002), remained after adjustment for age, smoking, marital status, presence of depression, and HbA1c (Beta-.109, P=0.007), and SHBG (Beta -0.077, P=0.017), but not after additional adjustment for BMI (Beta -0.022, P=0.504).

The results using OSA category rather than AHI were similar.

These data suggest that obesity, or sleep related factors rather than OSA per se, determine T. This accords with the graded effect of weight loss, but limited effect of CPAP to increase T and highlights the importance of managing obesity effectively, particularly in the context of OSA.