06 Jan Linking sleep disturbance to idiopathic male infertility
Recently published data suggests that male fertility has declined over the past four decades. The reasons for the decline are unclear with up to 50% of cases of male infertility remaining unexplained (idiopathic male infertility). Whilst environmental factors and rising rates of obesity have been implicated, there is now growing evidence that sleep disturbance may be an independent causative factor. Indeed, the prevalence of sleep disturbance appears to be increasing in parallel with deterioration in population sperm quality, a commonly used surrogate marker of male fertility.
Although there is some understanding of the relationship between sleep, gonadal hormone secretion and sexual function, it remains to be seen whether sleep disturbance is implicated in idiopathic male infertility. This review will detail the current evidence supporting a link between sleep disturbance and male infertility. Potential mechanistic pathways will be proposed and evidence supporting these pathways will be discussed. Further research is needed in clarifying links between sleep disturbance and idiopathic male infertility. Keywords: Sleep; Sleep disturbance; Infertility; Obstructive sleep apnoea; Reproductive hormones; DNA fragmentation; Male infertility
Infertility & sleep disturbance: current state of research
Most research conducted in the area of fertility and sleep disturbance has focused on females. For example, polycystic ovarian syndrome (PCOS), a common cause of female infertility characterised by anovulation, hyperandrogenemia and high rates of insulin resistance and obesity, has been associated with an increased prevalence of sleep-disordered breathing, independent of obesity.
The majority of published studies in men focus on the impact of sleep-disordered breathing on gonadal hormones (mainly testosterone). Certainly, several studies have demonstrated a negative correlation between testosterone levels and sleep apnoea, independent of BMI.
Early research demonstrating a relationship between sleep-related erections and testosterone levels led to further work supporting an association between sleep-disordered breathing and erectile dysfunction. Indeed, it has been shown that erectile dysfunction occurs in half of all men with OSA, independent of obesity.
Despite some understanding of the relationship between disturbed sleep, male sexual function and gonadal hormone secretion, it remains to be elucidated whether these putative mechanisms translate to clinically significant effects on male fertility. In particular, little is known regarding the effects of the various sequelae of sleep disturbance (sleep fragmentation, sleep restriction, circadian disruption or hypoxia) on male reproductive capacity (Fig. 1).
Sleep & idiopathic male infertility – potential mechanisms
- Hypoxia & oxidative stress
- Systemic inflammation
- Insulin resistance & dyslipidaemia
- Sleep restriction
- Circadian disruption
- Evidence suggests that male fertility has declined significantly over recent decades, the reasons for which remain unclear. Sleep and circadian biology are intimately linked with the normal biology of fertility therefore it is plausible that sleep disturbance negatively impacts on fertility.
- Although there is some understanding of the relationship between male reproductive hormones, sexual function and sleep disturbance, it remains to be shown whether a relationship exists between disturbed sleep and male fertility. In particular, the impact of the various domains of sleep disturbance (hypoxia, circadian disruption, sleep fragmentation and sleep restriction) on male fertility is not fully understood.
- Potential mechanistic pathways linking sleep disturbance and idiopathic male infertility include hypoxia, oxidative stress, systemic inflammation, aberrant reproductive hormone secretion, insulin resistance and dyslipidaemia.
- Observed impairments in male fertility and reproductive function in the setting of obesity and metabolic syndrome may be modulated by comorbid sleep disorders such as obstructive sleep apnoea or short sleep duration.
Gaurie Palnitkar, Craig L. Phillips, Camilla M. Hoyos, Anthony J. Marren, Mark C. Bowman, Brendon J. Yee, Linking sleep disturbance to idiopathic male infertility, Sleep Medicine Reviews, Volume 42, 2018, Pages 149-159, ISSN 1087-0792, https://doi.org/10.1016/j.smrv.2018.07.006. (http://www.sciencedirect.com/science/article/pii/S1087079217301557)