Aging men’s testosterone decline is largely due to the fact that older men sleep less well than younger men. Endocrinologists at the National University of Singapore reached this conclusion after studying 531 Chinese men aged between 29 and 72. The researchers measured the amount of testosterone in the men’s blood in the mornings, and asked the men about their sex lives and their sleep.
Sleep is healthy. Sleep an hour longer and your fat percentage goes down by three percent. More sleep improves your memory. That men sleep less as they get older, and the worse the quality of their sleep the less testosterone they produce, are known facts. But to what extent do older men produce less testosterone because they are sleeping worse?
Men make less testosterone as they age simply because their health declines. The higher your blood sugar level, cholesterol, triglycerides and uric acid, the lower your testosterone level. For this reason the researchers selected a group of healthy men, “with no known existing or history of major medical illnesses such as cancer, hypertension, thyroid dysfunction, diabetes, osteoporotic fracture and cardiovascular events as well as major sleep disorders”.
That the subjects were unusually healthy is reflected in the table below. The reduction in testosterone level (TotalT) and in bio-available testosterone (BioT) with increasing age is modest. Bio-available testosterone is testosterone that is not attached to the protein SHBG. Testosterone that is attached to SHBG loses its anabolic and pro-sexual properties.
After forty the concentration of DHEA declines drastically, while the concentration of estradiol increases. The concentration of DHEA correlated with sex: the higher their DHEA level, the more often the men had sex. When looking at the data on sexual activity, it’s worth bearing in mind that Singaporean men always score very low in sex surveys. Must be cultural.
And yes, there was a relationship between testosterone and sleep.
Men who slept less than 4 hours in a 24-hour period had about 60 percent less TotalT and 55 percent less BioT than men who slept longer than 8 hours. Extrapolating this you arrive at the following estimate: one hour extra sleep raises your testosterone level by 12-15 percent.
“The significant association of sleep with androgen concentrations suggests that sleep might be a contributing factor in the etiology of men with low concentrations of androgen”, the endocrinologists conclude. “Therefore, in the management of men with low androgen concentrations, an evaluation of their sleep hygiene might add to the understanding the etiology of their hypogonadal state.”