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The detrimental effect a lack of sleep can have on our cardiovascular system is still not widely recognised
Sleep. One of the most important factors in a person’s life. Most of us underestimate the negative impact of inadequate sleep and a growing body of literature is finding that a concerning percentage of the population are sleeping less than six hours a night. Simply put, that is not enough.
Not only does a lack of sleep have a big impact on our emotional, mental and neurocognitive health, it also wreaks havoc with our cardiovascular health, with inadequate sleep increasingly showing a tight relationship with weight gain, hypertension and a host of other adverse cardiometabolic parameters.
Unfortunately, as physicians we often overlook the influence of sleep when it comes to our patients’ cardiovascular health. More often, diet, weight and activity levels take priority, but poor sleep can be the lead domino to exert control on these other driving factors. Control of these parameters is most often about behaviour change, and behaviour change requires a proper state of mind. For me, the quality of my life is controlled by the quality of my thoughts and the quality of my thoughts is most often controlled by the quality of my sleep.
To illustrate this point is the outcome of probably the largest cardiovascular risk study ever conducted, on billions of people, without their consent, and which happens every year: The daylight savings time change. When an hour of sleep is lost by billions around the world, the average myocardial infarction rate goes up by about 24 per cent. Although it subsequently drops by about 21 per cent when an hour of sleep is gained later in the year, it certainly demonstrates the impact a single hour of sleep disturbance can have on human physiology. Additionally, the impact of this global ‘sleep bomb’ has a blast radius of about three days, with diminishing effects as each day passes. It is not limited to adverse cardiovascular events alone. Increased rates of suicide and road traffic accidents can also be seen, along with even harsher sentencing by judges.
With coronary artery calcification now recognised as one of the lead indicators of future cardiovascular risk, we can study poor sleep and its impact on such a biomarker and what we find is alarming. In a study for those getting five hours or less of sleep a night, a 200-to-300 per cent increased risk of coronary artery calcification was seen. Although there is undoubtedly a healthy user bias at play here, there are several plausible mechanistic reasons as to why poor sleep could drive such progression of cardiovascular disease.
We know that when the body is deprived of sleep, the sympathetic nervous system is overly-activated, which means more adrenaline is released, cortisol levels are higher and the growth hormone levels are dampened, all key drivers of atherosclerosis. Clear evidence links a lack of sleep with increases in blood pressure and when you are sleep-deprived, you tend to form bad eating habits and crave food likely to worsen your cardiometabolic health.
Inadequate sleep also drastically impacts an individual’s physiological ability to lose weight when dieting, with those sleeping six hours or less losing far less weight and 70 per cent of the weight lost being lean muscle mass rather than adipose tissue.
Human beings are the only species that deliberately deprive themselves of sleep for no apparent reason. Almost no other organisms on the planet undergo voluntary sleep deprivation.
Because of this, humans have not developed any compensatory mechanisms to counterbalance the physiological impacts of sleep deprivation. Many people also believe that if you are lacking sleep, you can simply ‘catch up’ on your sleep. You can’t. If you are ‘catching up’ on your sleep every weekend by sleeping an extra three hours, it is detrimental to your circadian biology. In fact, it is the same as flying from London to New York every weekend! There is no ‘safety net’ for insufficient sleep, as Mother Nature has never had to face the challenge of sleep deprivation.
While sleeping pills can be a very short-term answer to sleep deprivation, it is not recommended, nor is it fixing the root cause of the problem. The majority of pharmacological sleep aids do not produce natural sleep and have reliably been shown to increase longer-term risks of early mortality and cancer.
Now that my first question in a cardiometabolic screen relates to sleep, I have certainly identified a lead domino or causal factor in many patients that if not addressed, would have seriously limited any efforts to address the classical risk factors we commonly focus on. The next time someone asks about understanding their risk of heart disease, start with sleep. You will be surprised what you find.