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A review of studies concluded that have insomnia e sleep less than five hours a night can be harmful to health. That’s because sleeping well is an essential issue for health as a whole and that includes the cardiovascular part – for some years, sleep disorders have been associated with metabolic and heart problems.
Recently, an analysis reinforced this risk by concluding that people who sleep 5 hours or less per night have a 69% greater chance of having a heart attack than those who do not suffer from insomnia.
To reach this conclusion, the researchers reviewed more than 1,200 observational studies published between 1998 and 2019. These articles evaluated the association of insomnia with myocardial infarction and, after excluding biases, nine studies were selected for the final analysis.
Altogether, more than 1 million people with an average age of 50 years were included (those who suffered from sleep apnea, a known risk factor for heart problems, were excluded from the analysis). Of those, more than 153,000 had insomnia.
The results were published in the scientific journal Clinical Cardiology and presented at the scientific sessions of the American College of Cardiology during the American Congress of Cardiology (ACC), held in early March in the United States.
What is insomnia, actually?
Essentially, insomnia can be defined as:
- Persistent difficulty initiating sleep and falling asleep
- Difficulty consolidating sleep and staying asleep;
- Tendency to wake up early;
- Inability to go back to sleep — which results in some sort of daytime impairment.
In the study, researchers looked at all of these criteria as well as sleep duration. The problem is global: the World Health Organization (WHO) estimates that four out of ten people have some difficulty sleeping.
To make matters worse, cardiovascular problems are the main cause of death in the world and several studies have already shown that more than 80% of diseases could be avoided with the adoption of a healthy lifestyle and proper management of known risk factors.
Since the fall of last year, the American Heart Association has included quality sleep as one of the eight essentials for heart health. Thus, it was added to other important factors for the heart health checklist alongside items such as exposure to nicotine, physical activity, diet, weight, blood glucose, cholesterol and blood pressure.
But why is insomnia a risk factor?
Sleep is important not only for resting, but also for regulating the body in general — no wonder human beings spend a third of their lives sleeping. It is during sleep that our body organizes itself to carry out a series of metabolic and hormonal processes necessary for the cardiovascular system.
According to the cardiologist Juliana Soaresfrom the Hospital Israelita Albert Einstein, insomnia alters the neurohormonal axis, which involves the hypothalamus (region of the brain responsible, among other functions, for the production of hormones) and the adrenal and pituitary glands.
These glands produce hormones related to our daily activity and are also responsible for the production of cortisol, known as the “stress hormone”. Increased cortisol accelerates the process of atherosclerosis, which is the formation of fatty plaques inside the arteries that culminate in acute myocardial infarction.
Soares explains that cortisol increases in our body in situations of stress, fight and flight, and also due to insomnia. Some previous studies have already shown that patients who have a heart attack have elevations in cortisol levels prior to the event.
“Since insomnia is a situation that alters this neurohormonal axis and also raises cortisol levels, the hypothesis of a correlation with cardiovascular events arose,” said the cardiologist.
In the study, researchers evaluated four situations: those who slept less than 5 hours, those who slept 6 hours, people who slept 7 to 8 hours and those who slept more than 9 hours. And found that patients who sleep less than 5 hours have up to 69% greater risk of having a heart attack compared to those who did not have insomnia.
In addition, the study also showed that those who sleep 6 hours have a lower risk of heart attack compared to the group who sleeps less than 5 hours. However, the risk in this group is greater than in people who sleep 7 to 8 hours. And those who sleep more than 9 hours did not show a change in the results for cardiovascular disease.
“What we can say is that sleeping less than 5 hours considerably increases the risk of a heart attack and sleeping 7 to 8 hours a night was considered the ideal range of sleep for protection”, said Soares.
According to the expert, this is yet another study that corroborates the impact of sleep quality on cardiovascular health. In addition, it manages to establish the intervals of hours of sleep that are most harmful.
“We already had evidence of an association between sleep disorders and cardiovascular health. What we still didn’t know was to say which sleep intervals were at greater risk. And this study was able to show just that,” he said.
Soares also pointed out that people should pay attention to the quality of their sleep. “Traditionally, people are concerned about blood pressure, food, weight, cholesterol, but rarely are they concerned about sleep. And more and more science shows the importance of having quality sleep for health as a whole”, concludes the cardiologist.