At three months, only 15 men were still using the CPAP machine and reporting for follow-up analysis. By six months, only 8 men remained in the trial.
This large drop-out rate makes it difficult to evaluate long-term success.
CPAP machines are clunky and uncomfortable, and many patients with sleep apnea find them difficult to use in the long run.
Among those who persisted with treatment, however, sperm motility stayed above baseline; though as the sample size was small, the researchers caution against reading too much into it.
"Taken together, these findings support a conceptual model in which sleep-disordered breathing and local seminal microenvironmental inflammation are jointly associated with impaired sperm function in men with obstructive sleep apnea," the authors conclude.
The team is now calling for larger studies to "elucidate the precise molecular mechanisms and confirm the long-term fertility benefits of CPAP treatment."
The research has been published in Sleep Medicine.
