WE spend more than a quarter of our lives asleep and while personal experience teaches us that adequate sleep is necessary, research over the past decades is making clear how important adequate and high-quality sleep is for optimal health. An area that is receiving attention is the association between sleep disorders and the risk for heart disease.
This week we will look closer at this association. You may wonder why do we need to sleep at all? The initial studies looking at the need for sleep focused on the effects of sleep deprivation on the function of the brain. Inadequate sleep is associated with reduced cognition, slow reflexes, emotional ability, and difficulty with paying attention. Researchers believe that sleep is important for clearing waste products from brain cells. A process that is less efficient while awake. Importantly, sleep has been demonstrated to be important for what is called "brain plasticity" or the changing of the brain in response to a variety of inputs. Sleep is important for consolidating memory and for learning in general. Aside from the effects on the brain it has become clear that sleep has beneficial affects beyond functioning of the brain. A lack of sleep has been associated with immune deficiency, metabolic alterations (including elevated blood sugars), weight gain, depression, and a variety of different illnesses.
How does sleep affect my risk of heart disease?
Several large observational studies have found an association between heart disease and abnormalities in the amount and quality of sleep. Abnormalities in sleep can increase the incidence of various risk factors for heart disease or these abnormalities may be associated directly with heart disease themselves. Two disorders of sleep which have been associated with heart disease are insomnia and sleep apnoea. Insomnia can simply be thought of as not getting adequate amounts of sleep either secondary to difficultly falling asleep or having fallen asleep, difficulty maintaining the sleep state. Sleep apnoea is a disorder of sleep in which the patient repeatedly stops breathing. There are many causes of sleep apnoea of which the most common is obesity. The result of sleep apnoea is a reduction in the amount of oxygen in the blood during sleep which has a number of adverse effects on the body as a whole.
Insomnia and heart disease
Insomnia has been shown to be associated with an increased risk of hypertension. Sleeping less than six hours in a 24-hour cycle has been shown to increase the risk of hypertension four-fold. Insomnia has also been shown to increase various inflammatory markers in the blood including those associated with risk of laying down cholesterol in arteries. Both coronary artery disease and stroke risk is elevated in patients with insomnia with the level of risk varying with different populations studied. A registry from Taiwan which followed 40,000 patients for 10 years found patients with insomnia had a 68 per cent increased risk of heart attack and an 85 per cent increased risk of stroke. Insomnia is a common complaint among patients with congestive heart failure, but registry evidence has suggested that in patients with insomnia and no diagnosed heart disease, the risk of developing congestive heart failure may be up to five times that of patients with normal sleep duration. Lastly some studies have suggested that insomnia may increase the risk of dying of cardiac disease although this needs to be further studied.
Sleep apnoea and heart disease
Sleep apnoea increases both risk factors that lead to heart disease and can also directly increase heart disease itself. Sleep apnoea has been demonstrated to increase the risk of hypertension, type 2 diabetes, and elevation in blood cholesterol. Sleep apnoea has also been shown to increase the risk of heart arrhythmias by up to four times that of the normal population. Sleep apnoea is also thought to significantly increase the risk of congestive heart failure and coronary artery disease. The recurrent lack of oxygen in the blood because of disordered breathing is thought to elevate hormones responsible for the fight or flight response, to increase pressures in the heart chambers and to increase inflammation in the body.
How much sleep do I need?
The amount of sleep that an individual needs varies with age. Children and adolescents require more sleep that adults. It is estimated that adults need at least seven hours of sleep per night. Using this measure the National Heart Lung and Blood Institute of the United States estimates that one in three American adults (50-70million people) do not get enough sleep on an ongoing basis. It is important to note, however, that temporary disruptions in the amount and quality of sleep are extremely common and have been estimated to affect one in two American adults at some time during their lives. The figures for Jamaica are not known but it is expected to be similar or worse because of the impact of persistent socio-economic stressors in the causation of sleep disruptions and disorders.
What do I do if I am not getting enough sleep?
It is important to realise that most of us will have short term disruptions in normal sleeping patterns as part of life. For example, jet lag, emotional stress, and hospitalisation are well known causes of sleep difficulties and normally are not long-term issues. It is important to create an environment to promote healthy sleeping habits. Good habits would including having a regular sleeping and waking time which is consistent including weekends. The bedroom should be quiet, ideally cool and used only for sleeping or sexual activity. That is, we should avoid television or computer use in the bedroom. Computer screen used immediately prior to going to bed should be avoided. Do not consume alcohol, caffeine, and large meals in the hours before bedtime. Regular daytime exercise should be performed as this is associated with improved sleep duration and quality. The short term of sleeping tablets can be beneficial, however evidence suggests that long-term use can be associated with addiction, dependence, and reduced sleep quality. These medications can have significant side effects in the elderly and should be used with caution or avoided. For patients who continue to have difficulty with sleep that is an ongoing issue, they should seek medical advice for further evaluation and treatment.
How do I know if I have sleep apnoea?
Sleep apnoea can be suspected if you have been noted to have pauses in breathing when sleeping particularly when associated with loud snoring and obesity. Patients will often have symptoms of morning headaches or not feeling rested when awakening. Lethargy and falling asleep in the afternoon are also common symptoms. For patients with hypertension, atrial fibrillation and congestive heart failure, cardiologists will often have a high index of suspicion for sleep apnoea and may recommend testing. Treatment of sleep apnoea with a special equipment during sleep often results in improved sleep quality. Studies are ongoing to see if treatment lowers heart disease risk.
Deficiency in the amount of high-quality sleep is an important emerging risk factor of the development of heart disease. It is also important to note that it has other impacts on general health that we do not have space to discuss. Hopefully, you now have a better appreciation of the role that sleep plays in maintaining optimal health.
Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Correspondence to email@example.com or call 876-906-2107.