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Introduction

SLEEP is a fundamental vital function that takes approximately one third of man’s lifespan. Stress management and sleep are the well-known benefits, but it is also crucial for keeping the body and mind in good shape. Sleep, especially insufficient or the presence of some pathology connected with it, may affect the body’s circadian rhythm and thus contribute to abnormalities in different metabolic and hormonal processes. It may cause several things which the sick part did not mention, but all are unhealthy for the heart, high blood pressure, high sugar levels, high cholesterol, stress, anxiety, and depression. Infertility today has become a common problem in the last few decades and most of them arise from environmental and life style causes. Lack of sleep quality or sleep disorders, which depend on the late usage of such devices, shift work and exposure to noise, are among the worldwide tendencies that greatly influence these issues.

Physiology of sleep

There are also several sleep stages, the two basic ones being Rapid eye movement (REM) and non-rapid eye movement sleep (non- REM). Most adults sleep an average of 7 hours per night with some needing as long as 9-10 hours of sleep known as long sleepers and others termed short sleepers requiring < 6 hours. Sleep is controlled by homeostatic regulation which corresponds to the propensity to fall asleep and by circadian regulation which is under the control of the central clock located in the suprachiasmatic nuclei. Melatonin is the main hormone regulating these chronobiological rhythms.

Is there a correlation between sleep and reproductive physiology?

From various published studies, there is an association between shortened sleep duration, different chronotypes, irregular night shift work with the reproductive parameters.
The reproductive parameters considered are ovarian function, semen parameters, natural fertility and outcomes of IVF treatment.

The reproductive function of humans is regulated by several hormones which are secreted in synergy with the circadian timing of the body. Sleep patterns physiologically drive the synthesis, secretion and metabolism of hormones necessary for reproduction. i.e., estrogens, progesterone and androgens. Sleep deprivation among men and women is increasingly reported as one of the causes of infertility.

One crucial role of slow wave sleep is its hormonal function with the secretion of growth hormone and cortisol which drastically influences metabolism and inflammation.

Stress, sleep dysregulation and circadian dysrhythmia are also potential factors implicated in disturbing the balance of the reproductive hormone axis.
Sleep disturbance may be related to infertility through three possible pathways.

• HPA activation that precipitates sleep disturbance.
• Altered sleep duration and or sleep continuity resulting in further HPA activation.
• Circadian dysrhythmia

Melatonin is second generation hormone related to serotonin, secreted in night by pineal gland and is the main mediator of sleep. It is also produced by the granulosa cells and oocytes. Melatonin also has a role in scavenging free radicals making it a powerful protector of oocytes against oxidative stress and has therefore uses as a treatment for premature ovarian failure . Melatonin is also thought to have a role in testicular function through its action on the secretion of gonadotropin-releasing hormone and direct antioxidant and anti-inflammatory effects at the testicular level. Melatonin levels in plasma also affects sperm motility.

Stress also can compromise the immunity in couples who are anxious to conceive- be it natural or through assisted methods. Cytokine and immune inflammatory responses marked by TNF and IL-6 have been observed to increase during sleep disturbances along with elevated C-reactive protein (CRP) in young couples.

Men

Sleep deprivation generates stressful stimuli intrinsically due to circadian desynchrony and thereby increases the activation of the Hypothalamus-Pituitary Adrenal (HPA) axis, which, consequently, increases the production of corticosterone. The elevated level of corticosteroids results in a reduction in testosterone production, reduced sperm motility and apoptosis of the Leydig cells.

Based on very scientific and structured sleep study parameters such as the Karolinska sleep questionnaire and the Pittsburg Sleep Quality Index, it was found that reduced sleep duration and /or poor quality of sleep had direct correlation or impact on:

• sperm parameters such as motility, count and morphology.
• It has also been linked to sexual dysfunction.
• Other chronic conditions precluding sexual function such as obesity, diabetes, cardiovascular disease and depression

• Common factors that contribute to lack of sleep and fertility problems in men include alcohol, smoking and stress.

Women

Sleep disturbances disproportionately affects women more compared to men. Reproductive transitions in a female lifespan (menarche, pregnancy, menopause) makes a woman more vulnerable to it and thought to precipitate sleep continuity disturbance, hence heightening women’s risk for sleep problems throughout their lifespan

Poor sleep quality and / or sleep duration has been found to have a profound impact on several reproductive functions and parameters.

• Menstrual cycle irregularity
• Premenstrual syndrome
• Obesity
• PCOS
• Reduced ovarian reserve
• An association has been found between sleep disorders and women undergoing treatment for infertility, especially less number of oocytes retrieved in the IVF cycle.

Conclusion

To summarise, the factors affecting sleep quantity or quality, sleep deprivation, and/or disordered sleep, can exert an effect on a number of different hormones involved with reproduction mainly those along the HPA axis and also anti-mullerian hormone. The synchrony of these hormones is essential for successful ovulation, conception, and implantation and therefore, one can conclude that sleep continuity disturbance could play a significant role in interfering with the hormonal milieu necessary for reproduction. Sleep and its dysfunctions’ being inter related to fertility definitely makes it a very modifiable target to improve the outcomes of fertility treatment along with stress management by way of counselling, lifestyle and dietary modifications, antioxidant adjuvants and in some cases allied therapy such as acupuncture.

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