Sleep + testosterone levels
Testosterone levels fluctuate according to circadian rhythms, meaning they’re higher in the morning when you wake up and lower at the conclusion of the day. Recent research has found that, contrary to the original hypothesis that testosterone is controlled in an “endogenous” (or internal) rhythm (like with cortisol), it is actually dependent on sleep—specifically on sleep reaching its peak during the first three uninterrupted hours asleep (just around the time of the first REM sleep episode). If sleep is fragmented, testosterone levels don’t increase as they should. (1)
In a study conducted at The University Of Chicago and published in JAMA, men who slept fewer than five hours a night for one week were found to have 10 - 15% lower levels of testosterone than when they had a full night’s sleep. (2) To put this in context, normal aging is associated with a 1-2% decrease in testosterone levels per year, according to the NIH. (3)
Because testosterone is associated with energy, libido (i.e. sexual desire/sexual arousal), sexual performance, concentration, and fatigue, the effects of lack of sleep, poor sleep, or more serious sleep problems can be broad-reaching, affecting mental health and overall quality of life.
“Low testosterone levels are associated with reduced well being and vigor, which may also occur as a consequence of sleep loss. As research progresses, low sleep duration and poor sleep quality are increasingly recognized as endocrine disruptors.” (4)Eve Van Cauter, PhD, one of the study’s lead researchers
Sleep and erectile dysfunction
Erectile dysfunction (ED) affects over 30 million men in the United States, and prevalence only increases with age; 47% of those over 60 experience symptoms. (5) Urology sleep studies have also indicated that the rate of ED is higher in men with Obstructive Sleep Apnea Syndrome, a health condition that occurs when throat muscles relax, partially (hypopnea) or completely (apnea) blocking the airway and leading to snoring or feelings of gasping for breath (this is where CPAP therapy—or continuous positive airway pressure—can be helpful). In one clinical trial, 63% of male patients with OSA (who were in good health with no other comorbidities) were also suffering from ED, compared to 47% of those without OSA—thus confirming the sleep disorder as a clinically significant risk factor. (6)
Apnea exists on a spectrum, meaning it doesn’t manifest the same way for everyone. Some experience mild, general snoring due to upper airway resistance that doesn’t affect blood oxygen levels while others have more severe cases in which blood oxygen levels drop. Known as hypoxemia, this stresses out the entire body and can lead to hypertension, stroke risk, and cardiovascular disease. In a sexual health/sleep medicine study of 2,676 men aged 67 or older, researchers concluded that those with hypoxemia have a higher risk of experiencing moderate or complete erectile dysfunction, a correlation largely explained by higher body mass index (BMI)/obesity and increased comorbidity among men with sleep-disordered breathing. (7)
To learn more about the symptoms of OSA (as well as other sleep disorders), refer to our guide on when to seek medical advice from a sleep specialist.
Another sleep-related factor that may influence erectile function is non-standard shift work (i.e. work starting before 7am or after 2pm), which studies have shown increases the chances of hypogonadism, or lower serum testosterone levels, a side effect of which is ED. (8)
Sleep and athletic performance
Without enough sleep, energy levels suffer. And even if you do work up the motivation to exercise, doing so in a sleep-deprived state means you’ll likely get tired even earlier (9) and your physical performance will suffer.
In a study conducted at Stanford University, researchers asked 11 healthy students on the men’s basketball team to maintain their habitual sleep-wake schedule for 2-4 weeks in order to get a baseline for reaction time, levels of daytime sleepiness, and mood. What followed was a 5-7 week period of “sleep extension” in which they slept a minimum of 10 hours/night—representing an average increase of 110 minutes. (10)
Results showed that, during the sleep extension period, athletes demonstrated:
- Faster timed sprint: 16.2 seconds at baseline vs 15.5 during sleep extension
- Improved shooting accuracy: 9% increase in free throw percentage + 9.2% increase in 3-point field goal percentage
- Improved overall ratings of physical and mental well-being during practices and games
Sleep and lower urinary tract symptoms
Lower Urinary Tract Symptoms (or LUTS, for short) manifests with symptoms including incomplete bladder emptying, straining to urinate, increased frequency of urination, and poor stream. Understandably, the condition also causes frequent sleep disturbances (known as “nocturia”). However, certain studies point to the fact that while LUTS certainly contributes to poor sleep, the reverse may be true as well: poor sleep—specifically due to OSA—exacerbating LUTS. (11)
Sleep and male fertility
Interestingly, male fertility is affected by both too much and too little sleep—both of which cause men to be more at risk for infertility than those averaging between 7-8 hours per night. It’s for this reason that researchers consider the relationship U-shaped rather than linear.
In one study, (12) researchers enrolled 1,176 couples who had been attempting to conceive for up to 6 cycles. They split the participants into cohorts based on the hours of sleep received per night, and from there assessed the respective fecundability ratios (FR), or the probability of conception within 12 months. Here’s what they found in comparison to the control group of men who slept 8 hours per night:
- <6 hours = 0.62% probability of conception
- 6 hours = 1.06% probability of conception
- 7 hours = 0.97% probability of conception
- >9 hours = 0.73% probability of conception
This led them to conclude that both short and prolonged sleep duration negatively impact fecundability, or the probability of conception occurring.
For science-backed advice and tips on how to get better sleep, refer to the following: