Sleep Apnoea and Testosterone: Why Treating One Does Not Fix the Other

A man of 47 is told his testosterone is 8.4 nmol/L. He is exhausted, carrying three stone more than he was at thirty, and his wife has been telling him for years that he stops breathing at night.

Nobody asks about the breathing. The conversation goes straight to testosterone.

This is the most commonly missed part of a low testosterone workup, and the reason it gets missed is that the man arrives complaining about tiredness rather than about his airway. But the relationship between sleep apnoea and testosterone is not the simple one most articles describe, and getting it wrong sends men down the wrong path in both directions.

What obstructive sleep apnoea actually is

During sleep the muscles of the throat relax. In some people the airway narrows enough to reduce airflow, or closes completely. Breathing stops, oxygen falls, and the brain briefly wakes to restore the airway. Then it happens again.

This can occur dozens of times an hour, all night, for years. The man does not remember waking, because these arousals are too brief to reach conscious memory. What he experiences is eight hours in bed and no refreshment from any of it.

It is common, particularly in men carrying extra weight around the neck and middle, and it is substantially underdiagnosed, because the main symptom people report is tiredness rather than anything to do with breathing.

Why it should lower testosterone

The mechanism is genuinely sound.

Most of a man's daily testosterone is produced during sleep, in pulses tied to the deeper stages. That production needs uninterrupted sleep architecture. Sleep apnoea shreds it, pulling the sleeper repeatedly out of deep sleep before the process completes.

The supporting evidence is strong. Restrict healthy young men to five hours a night for one week and daytime testosterone falls by roughly ten to fifteen per cent. That is one week, in men with nothing wrong with them. Sleep apnoea does something more disruptive, every night, for years.

Men with obstructive sleep apnoea do consistently have lower testosterone than men without it. That association is well established.

Which is why what follows is surprising.

Treating the apnoea does not raise testosterone

This is the part most articles get wrong, including, until I checked it properly, one of mine.

CPAP is the standard treatment: a machine delivering pressurised air through a mask, holding the airway open. It works. It stops the apnoeas, restores sleep architecture, and for many men transforms daytime function.

It does not meaningfully raise testosterone.

Two separate meta-analyses have examined this. A 2014 analysis pooling seven studies and 232 men found no significant change in total testosterone after CPAP. A 2019 analysis of twelve studies and 388 men found the same, with the result holding even when men who were hypogonadal at baseline were analysed separately, and even in studies running longer than three months.

The authors of the later review were direct about what this implies: the finding does not support a direct causal interaction between sleep apnoea and testosterone, and strategies other than CPAP should be considered when managing low testosterone in these men.

So what is actually going on

The most probable explanation is that both conditions have a common cause sitting underneath them, and that cause is excess weight, particularly visceral fat.

Fat around the neck and upper airway narrows it and makes collapse during sleep more likely. Fat around the middle contains aromatase, converting testosterone to oestradiol, and drives the metabolic changes that suppress the signal from brain to testes. Why belly fat will not budge covers that loop.

So a man with significant visceral fat tends to develop both problems. Treating one of them with a machine does not address the thing generating both.

This also explains the clinical observation that weight loss improves apnoea and raises testosterone, while CPAP improves apnoea and leaves testosterone roughly where it was. Notably, CPAP alone does not reliably produce weight loss either.

The complication running the other way

There is a second reason this matters, and it points in the opposite direction.

Testosterone therapy can worsen obstructive sleep apnoea. A randomised placebo-controlled trial in obese men with severe apnoea found testosterone worsened breathing measures in the early weeks of treatment, and the effect appeared to diminish over time. Clinical guidance reflects this: untreated severe sleep apnoea is listed as a condition requiring caution before starting testosterone therapy.

Put the two findings together and the practical picture is clear.

• Treating apnoea will not fix the testosterone
• Treating the testosterone may worsen the apnoea, at least initially
• Both problems frequently share one underlying driver

Which is why the sequence matters more here than in most of these decisions.

How to tell whether you have it

You cannot diagnose this yourself, but you can work out whether it needs investigating. The strongest indicators:

• Loud snoring, particularly if someone has described pauses or gasping
• Witnessed pauses in breathing, which is the single most useful piece of information and usually comes from a partner
• Waking unrefreshed after adequate hours in bed
• Daytime sleepiness, especially falling asleep unintentionally
• Morning headaches or a dry mouth on waking
• Nocturia, waking repeatedly to pass urine
• High blood pressure, particularly if difficult to control
• A collar size above about 17 inches

Screening questionnaires such as STOP-BANG are widely used and take two minutes, but diagnosis requires a sleep study, either at home or in a laboratory. If several of the above apply to you, that referral is worth asking for. Why you wake up tired after eight hours covers the wider picture of unrefreshing sleep.

What to do with this

The order below reflects what the evidence supports, rather than what is quickest.

Get the apnoea diagnosed and treated on its own merits. Not because it will raise your testosterone, because it probably will not, but because untreated apnoea carries real cardiovascular and cognitive consequences and makes you dangerous behind a wheel. That justification is sufficient by itself.

Address the shared driver. If visceral fat is present, weight loss is the intervention that plausibly improves both. It is slower and harder than a machine or a prescription, and it is the only one acting on the cause.

Retest testosterone after the apnoea is treated, properly, with two morning samples. Sleep will be better and any earlier reading was taken in disrupted conditions. Expect the number to be similar; treat what you find.

If testosterone is still low and TRT is being considered, say clearly that you have apnoea. This changes the risk conversation. It does not necessarily prevent treatment, but treated apnoea and untreated apnoea are different starting positions.

If you are already on TRT and your sleep has worsened, raise it. Snoring that has appeared or worsened since starting is worth investigating rather than accepting.

What causes low testosterone covers the other candidates, and the blood test guide covers testing properly.

The honest summary

Sleep apnoea is the most commonly missed finding in men being assessed for low testosterone, and it should be looked for in every man who snores heavily or wakes unrefreshed.

But it should be looked for because it is a serious condition in its own right, not because treating it will lift a hormone level. The evidence says it will not. What most likely links the two is the weight both conditions grow from, and that is the thing worth working on.

Common questions

Does sleep apnoea cause low testosterone?

Men with sleep apnoea consistently have lower testosterone, but treating the apnoea with CPAP does not raise it in pooled analyses. The most likely explanation is that excess weight drives both conditions.

Will CPAP raise my testosterone?

Probably not. Two meta-analyses covering more than 600 men between them found no significant change, including in men who were hypogonadal to begin with, and in studies lasting over three months.

Then why bother treating apnoea?

Because untreated obstructive sleep apnoea carries cardiovascular risk, impairs concentration and memory, and substantially raises the risk of falling asleep at the wheel. Those reasons stand entirely on their own.

Can TRT make sleep apnoea worse?

It can, particularly early in treatment and in men with severe untreated apnoea. Clinical guidance advises caution in this group, and any new or worsening snoring after starting testosterone should be reported.

What actually improves both?

Weight loss, where excess visceral fat is present. It reduces apnoea severity and raises testosterone, because it acts on the driver rather than on either downstream problem.

How do I get tested for sleep apnoea?

Through your doctor. Screening questionnaires such as STOP-BANG take two minutes, but diagnosis needs a sleep study, which is often done at home now rather than overnight in a laboratory.

Sources: Cignarelli A et al., Effects of CPAP on testosterone levels in patients with obstructive sleep apnea: a meta-analysis study, Front Endocrinol 2019;10:551 · Zhang XB et al., Efficacy of continuous positive airway pressure on testosterone in men with obstructive sleep apnea: a meta-analysis, PLoS One 2014;9(12):e115033 · Hoyos CM et al., Effects of testosterone therapy on sleep and breathing in obese men with severe obstructive sleep apnoea: a randomized placebo-controlled trial, Clin Endocrinol 2012;77(4):599-607 · Leproult R, Van Cauter E, Effect of 1 week of sleep restriction on testosterone levels in young healthy men, JAMA 2011;305(21):2173-4 · Bhasin S et al., Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline, J Clin Endocrinol Metab 2018;103(5):1715-44 · Educational only, not medical advice.

Keep reading: What causes low testosterone · Why you wake up tired after eight hours · Why your belly fat will not budge · The 90-minute sleep rule · Blood test: what to check · Free 2-minute testosterone test