Sweet Dreams

You've probably heard that 8 hours of sleep each night is important to your health, but did you know that insufficient sleep is linked to increased instance of chronic diseases and conditions? When looking at your overall health, the amount of sleep you get each night is as important as the foods you choose to put in your body, and whether or not you exercise.

Scientists report that individuals who consistently do not get enough sleep are linked to increased risk of obesity, type 2 diabetes, heart disease, high blood pressure and depression, among other chronic diseases and conditions. All of this can mean decreased life expectancy.

The Division of Sleep Medicine at Harvard Medical School has conducted 3 types of studies researching the link between sleep duration and chronic disease:  sleep deprivation studies, cross-sectional epidemiological studies, and longitudinal epidemiological studies.

The first study on sleep deprivation involves taking healthy research volunteers and depriving them of sleep to study the short-term effects on their bodies and minds that could potentially lead to disease. Such studies have revealed increased instances of stress, leading to high blood pressure, unstable blood glucose and inflammation.

The second type, cross-sectional epidemiological study, involves a large population of volunteers completing surveys about sleep duration patterns, and then looks at the presence of diseases. These resulted in high blood pressure, obesity and type 2 diabetes.

The longitudinal epidemiological study appears to be the most thorough study looking at sleep disturbance and chronic disease. This involves a group of healthy individuals who volunteer to have their sleep habits and disease patterns tracked over a long period of time. Analysis of this ongoing study indicates that adjusting sleep duration can decrease risk of developing chronic diseases, and lessen the severity of an ongoing disease.

When looking at obesity, studies show that individuals who consistently sleep less than 6 hours per night have a higher body mass index (BMI), while those who sleep 8 hours have the lowest BMI. The explanation for this has to do with hormones. While we're sleeping, our bodies secrete hormones that control our appetites, metabolism and blood glucose processing. Too little sleep and this balance is disrupted. Sleep deprivation is also linked to increased levels of cortisol, the "stress hormone," and increased insulin secretion. Insulin is the hormone that regulates glucose processing and fat storage, meaning more insulin = more fat and higher risk of type 2 diabetes. Insufficient sleep is also linked to decreased levels of leptin, the hormone that makes us feel full when eating. As if that's not bad enough, lack of sleep also increases the appetite-stimulating hormone, ghrelin. 

Studies have shown that just one night of inadequate sleep can result in increased blood pressure the next day, explaining the risk between habitual sleep deprivation and cardiovascular diseases and strokes. For women in particular, less than 6 hours of sleep OR more than 9 hours of sleep can increase the risk of heart disease. Cardiovascular disease and stroke can also result from the development of sleep apnea, when an individual's airway closes multiple times during sleep, causing them to wake several times during the night.

You may notice that you feel more irritable during the day if you've had poor sleep the night before. Well, this is not your imagination... Studies have linked getting less than 5 hours per night with chronic mood disorders such as anxiety, depression and mental distress. Research volunteers reported increased instances of feeling angry, sad and anxious. Another study showed volunteers had less optimism and were far less sociable on lack of sleep.

When you're sick or your immune system is compromised, you might feel more fatigued. This is a good thing if you get the rest your body is begging for, as inactivity and sleep have shown to lessen severity and duration of illness. Sleep is important for preventing illness too - one study showed animals who got more sleep and were then faced with microbial infection had a better chance of survival than the animals who had less sleep.

Vital for good health, sleep is not a luxury, it is a necessity.