- Design
- systematic review and meta-analysis of nine observational studies, Newcastle-Ottawa risk of bias assessment
- Population
- 913 men for erectile function outcomes and 325 for hormonal outcomes, with sleep apnoea or shift work sleep disorder
- Primary outcome
- International Index of Erectile Function score, testosterone, follicle-stimulating and luteinising hormone
- Effect
- erectile score about 14.4 in sleep apnoea vs 17.5 in shift work; testosterone about 7-9 vs 20 nmol/L; I² 97.3%
Nine studies were pooled to compare male sexual and hormonal function across sleep disorders, with subgroup analysis separating obstructive sleep apnoea from shift work sleep disorder. Seven studies (913 men) contributed erectile function scores and a smaller subset (325 men) hormonal data.
Pooled erectile function scores averaged around 16 on the International Index of Erectile Function, in the moderate dysfunction range, with the sleep apnoea subgroup lower (about 14.4) than the shift work subgroup (about 17.5). Hormonally the gap was wider: testosterone around 7 to 9 nmol/L in sleep apnoea against about 20 nmol/L in shift work, with follicle-stimulating and luteinising hormone both higher in the apnoea group.
The heterogeneity figure is the one to read first. I-squared of 97.3% means the included studies disagreed almost completely, so the pooled score of 16 describes essentially none of them and should not be quoted as a finding. The subgroup contrast survives that criticism better than the pooled estimate, because the difference between groups is large, but it remains a comparison of separate study populations rather than of men measured the same way.
What this supports is a question, not a treatment. A man presenting with erectile dysfunction, particularly with low testosterone and a raised gonadotrophin pattern, is worth asking about snoring, witnessed apnoeas and daytime sleepiness — and the finding that even mild apnoea tracked with reduced erectile performance argues against dismissing a mild result. It does not show that treating the apnoea restores function, which no study here tested.
- Ask about snoring, witnessed apnoeas and daytime sleepiness in men presenting with erectile dysfunction
- Consider sleep assessment where erectile dysfunction accompanies low testosterone, particularly in an obese man
- Do not tell patients that treating sleep apnoea will restore erectile function; no study here tested that
- Treat the pooled erectile function score as uninformative — heterogeneity was 97.3%
- Take a mild apnoea result seriously rather than dismissing it as insufficient to explain symptoms
Why it matters
Erectile dysfunction is often the first thing a man will come in about, and the sleep history is rarely taken.
Don't overread it
These are observational associations with extreme heterogeneity — they cannot show that sleep apnoea causes the dysfunction or that treating it helps.
The statistics, in plain English
An I-squared of 97.3% means almost all of the variation between studies is real disagreement rather than chance, so pooling them produces a number that represents no actual population. The subgroup comparison is more interpretable because the difference is large, but it compares men from different studies rather than randomising or matching them — and men with sleep apnoea differ from shift workers in obesity, age and comorbidity, any of which could account for the testosterone gap. All nine studies were observational.
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