Sleeping less than 5 hours can bring various chronic diseases

We know that sleeping less can affect our health and longevity, but did you know sleeping less can affect the future development of chronic diseases?

Sleeping and disease

Sleep affects our ability to function throughout the day. After all, everyone has experienced fatigue, bad mood, or lack of focus that often follows a night of poor sleep.

In many cases, people are unaware that sleep deprivation has long-term health consequences, including chronic diseases such as diabetes, high blood pressure and heart disease. These conditions may lead to a decreased life expectancy. Moreover, studies show that too much sleep is also harmful [1].

The connection between sleep duration and chronic illness

Three main study types help us understand the relationships between sleep habits and the risk of developing certain conditions. The first kind, also known as sleep deprivation studies, includes depriving healthy research volunteers of sleep and analysing any short-term physiological changes that could trigger the disease.

Such studies have revealed various potentially adverse effects of sleep deprivation usually linked with increased stress, such as increased blood pressure, inflammation and impaired blood glucose control.

The second type of research, or cross-sectional epidemiological studies, includes examining questionnaires that give details of regular sleep duration and the existence of a significant disease or group of diseases in huge populations at one point in time. Diabetes, obesity, and hypertension are linked to reduced and increased sleep duration, as reported on questionnaires.

A lot of us have pulled an all-nighter or two in our lives. Sometimes it’s because of work or school; other times, it’s because you can’t stop binge-watching that new series on Netflix — Photograph: Tero Vesalainen/Shutterstock

Despite that, cross-sectional studies cannot define how too little or too much sleep directs to disease because people may have a condition that affects sleep instead of a sleep habit that makes illness occur or worsen.

Observations of sleep habits and disease patterns in initially healthy individuals over extended periods (longitudinal epidemiological studies) provide the third and most convincing evidence linking long-term sleep habits to development of various illnesses.

We have yet to determine whether adjusting one’s sleep can lower the risk of ultimately developing an illness or lessen the severity of an ongoing disease. Although, the effects from longitudinal epidemiological studies are starting to suggest that this is likely.

New study on sleeping and disease linkage

A new study says that people aged over 50 who slumber for five hours or less every evening might be at increased risk of developing multiple chronic diseases. The peer-reviewed research, reported in the publication PLOS Medicine, examined 8,000 civil servants in the UK who had no chronic illness at age 50 over 25 years [2].

During that period, scientists of the study asked the participants to account for how much amount of snooze they got every four to five years for monitoring. According to study results, individuals who slept five hours or less faced a 30 per cent higher risk for chronic diseases than those who got at least seven hours of sleep.

By age 70, the likelihood of people sleeping less than five hours bumped to a 40 per cent greater risk. As people age, their “sleep habits and structure change,” according to Severine Sabia, study lead author and a researcher at the University College London’s Institute of Epidemiology and Health [3].

The chronic diseases pursued in the study included: arthritis, cancer, chronic kidney disease, coronary heart disease, dementia, depression, diabetes, stroke, heart failure, chronic obstructive pulmonary disease, liver disease, mental disorders and Parkinson’s.

In the busy modern world, combing work, socialising and household chores can push getting a good nights sleep to the lower end of your to-do list. — Photograph: Shvets Production/Pexels

In old age and midlife, short sleep duration is linked with chronic disease onset and multimorbidity. In addition, the study findings support the preference of good sleep hygiene on primary and secondary prevention by targeting behavioural and environmental conditions that affect sleep quality and duration.

The study’s findings mirror previous research released by the US CDC (Centers for Disease Control and Prevention). It determined that older adults who do not complete seven to nine hours of sleep have a higher chance of getting chronic diseases, as well as obesity and high blood pressure [4].

Sleeping and obesity link

Various studies have connected insufficient sleep and weight gain. For instance, research has shown that individuals who usually sleep less than six hours every night are more likely to have a higher than average BMI (body mass index) and that those who get around eight hours have the lowest BMI.

Sleep, along with overeating and lack of exercise, is now considered a risk factor for obesity. Studies into the mechanisms included in regulating metabolism and appetite is starting to explain the link between obesity and sleep.

During sleep, our bodies produce hormones that aid in controlling appetite, energy metabolism and glucose processing. Getting too little sleep disturbs the balance of these and other hormones.

For example, poor sleep increases cortisol production, which is typically called the “stress hormone.” Poor sleep is also linked with aggravated insulin secretion after a meal. Insulin is a hormone that modifies glucose processing and promotes fat storage – higher insulin levels are linked to weight gain, which is a diabetes risk factor.

Inadequate sleep is also linked with reduced leptin levels, a hormone that signals the brain that it has enough food, and raised levels of ghrelin, a biochemical that prompts appetite. As a result, poor sleep may prompt food cravings even after eating an adequate amount of calories.

Sweets are most likely to be eaten to satiate the craving for a quick energy boost. In addition, insufficient sleep may also leave us feeling too tired to burn off these extra calories with exercise.

Sleeping and diabetes connection

Studies found that unsatisfactory sleep may lead to type 2 diabetes by manipulating how the body processes glucose, the high-energy carbohydrate cells use for fuel. One short-term sleep restriction study discovered that a group of healthy subjects who had their sleep shortened from 8 to 4 hours a night processed glucose slower than they did when they had a longer time to sleep (12 hours).

Various epidemiological studies also have revealed that adults who usually sleep less than five hours per night have a significantly increased risk of having or developing diabetes. In addition, researchers have correlated obstructive sleep apnea, a disorder in which breathing difficulties during sleep lead to frequent arousal, with the development of impaired glucose control similar to that which happens in diabetes.

Sleeping, hypertension and heart disease

Similarly, studies found that a singular night of inadequate sleep in people with hypertension can initiate elevated blood pressure through the following day. This effect may start to explain the relationship between poor sleep stroke and cardiovascular. For instance, a study reported that sleeping too little (less than six hours) or too much (more than nine hours) raised coronary heart disease risk in women.

There is also growing evidence of a link between obstructive sleep apnea and heart disease. Individuals with apnea typically experience multiple awakenings each night due to the closing of their airways when they sleep.

In addition to these sleep disruptions, apnea sufferers also undergo brief surges in blood pressure each time they awaken. Over time, this can develop into the chronic elevation of blood pressure, also known as hypertension, a significant cardiovascular disease risk factor. Luckily, blood pressure may go down following sleep apnea treatment.

Sleeping and mood disorders relation

Noted that one sleepless night can cause people to be moody and irritable the next day, it’s likely that chronic inadequate sleep may lead to long-term mood disorders. Chronic sleep issues correlate with anxiety, depression and mental anguish.

In one study, subjects who slept four and a half hours a night disclosed feeling more angry, sad, mentally exhausted and stressed. In another research, subjects who slept four hours every night displayed diminishing levels of sociability and optimism, as a function of days of inadequate sleep. These self-reported symptoms improved when subjects returned to a regular sleep schedule.

Sleeping and immune function link

It is normal for individuals to go to bed when they are feeling ill. Substances created by the immune system to fight off infection also induce fatigue.

One theory claims that the immune system evolved “sleepiness-inducing factors” because sleep and inactivity provided a benefit: people who slept more when suffering from an infection were better able to fight that infection compared to those who slept less. Animal research suggests that those animals who get more deep sleep after an experimental challenge by microbial infection have a higher chance of survival.

Life expectancy and sleep

Considering the multiple potential adverse health effects of inadequate sleep, it is not surprising that poor sleep is linked with lower life expectancy. Data from three extensive cross-sectional epidemiological studies reveal that sleeping five hours or less per night increased mortality risk from all causes by roughly 15 per cent.

Definitely, just as sleep issues can influence disease risk, some illnesses can also affect the quantity of sleep we get. While a projected 50 to 70 million Americans suffer from some sleep disorder, most individuals do not mention their sleeping concerns to their health providers, and most don’t inquire about them. This prevalent lack of awareness of the effects of sleep concerns can have serious and costly public health consequences [5].