For several decades sleep is a well established modulator of hormonal release, glucose metabolism and cardiovascular function. Sleep deprivation leads to various health related issues, which includes cardiac, metabolic and mental disorders. Weight gain, insulin resistance, type 2 diabetes, high blood pressure, and cardiac diseases occur more often in people having inadequate sleep.
Apart from duration of sleep, regularity in sleep timing has also been found to be important for a better health and increase in cardio metabolic disorders was documented in people with irregular sleep pattern in a recently published research. As these disorders make a large group of co-morbidity and health related burden, addressing their causes and preventive aspects would be quite helpful.
Sleep and hormonal regulations –
The release of the hormones of the hypothalamamic–pituitary–adrenocortical (HPA) system is inhibited whereas the release of growth hormone (GH) and prolactin is increased. Both GH and cortisol have important roles in glucose metabolism.
Sleep duration plays an important role in the regulation of leptin and ghrelin levels in humans whereas they decrease leptin level and increase ghrelin, which in turn regulate appetite and are important in pathogenesis of obesity.
Circadian rhythm and sleep –
Circadian rhythm which is like the internal clock of the body, has been derived from the Latin term “circa diem” which means “approximately one day”. This clock is set at nearly over 24 hours. Sleep as well as most biological processes, including hormone production, metabolism, core body temperature variations, are regulated by it. This clock is normally highly synchronized to environmental factors, the strongest of them being the light-dark cycle. Most individuals have a biphasic pattern in this cycle, with a mid-day decrease in alertness around 2–4 pm, followed by an increased alertness during mid to late evening which finally decline to the lowest levels in night. Almost all physiological systems in humans run nearly over a 24 hour cycle. Disturbance of this well-regulated circadian rhythm can lead to various sleep disorders resulting in poor health.
Metabolic Consequences of Shift Work Disorder –
Circadian misalignment because of shift work has been associated with obesity, diabetes, and cardio-vascular diseases. A Swedish study involving shift workers for 15 years reported increased risk for ischemic heart disease as compared to daytime workers. Another study has found that shift work is the most significant source of ischemic heart disease accounting for over 10% of mortality in men and over 5% in women. Higher triglyceride levels, lower HDL levels, and more obesity have been documented in the shift workers than daytime workers.
Mechanism by which shift work can cause metabolic dysregulation are not clear however it appear to involve hormonal alterations and increased sympathetic drive resulting in decreased insulin sensitivity and insufficient beta-cell compensation. Thus shift work which is strongly associated with irregular sleep pattern is associated with several cardio metabolic disorders.
In a recently published article in Scientific reports, Lunsford-Avery and team examined the sleeping patterns of 1978 adults, who had no history of sleep disorders. The investigators evaluated the link between bedtime patterns and markers of cardiometabolic risk, and they calculated a 10-year projected risk of heart disease, obesity, hypertension, and type 2 diabetes markers, such as high blood sugar and HbA1C.
Overall, people with irregular bedtimes had a higher body mass index (BMI), higher levels of blood sugar, higher blood pressure, and higher levels of hemoglobin A1C, and they were more prone to have a heart attack or stroke in the following decade than individuals with regular sleeping patterns. Also, the individuals who went to bed and woke up at varying times had a higher risk of depression and stress than their more disciplined counterparts.
Sleep plays a vital role in cardiovascular health and metabolism. Whereas sleep deprivation is well known to affect health adversely irregular sleep pattern doesn’t seem to be far behind in increasing the comorbities. Regular bed time not only ensures a sound sleep but also is a positive modulator in cardio metabolic processes. A well said phrase “early to bed and early to rise – keeps you healthy wealthy and wise” seems quite scientific and should be incorporated in life to remain disease free.