Why is sleep important?

Somewhere around 50-70% of adults in the US chronically suffer from some sleep disorder or sleep deprivation, hindering daily function and adversely affecting their health and longevity. There have been multiple studies to look at the association of sleep deprivation with chronic disease & all-cause mortality.

There is an association between chronic sleep deprivation and cardiovascular disease, hypertension, stroke, heart attack, obesity, diabetes, depression, anxiety & increase suicide risk. A few studies (see here and here) observed a J shaped curve when looking at the association between all-cause mortality, cardiovascular disease or stroke and sleep duration (see this figure). This basically means that if you sleep too much or too little your risk of all-cause mortality, cardiovascular disease and stroke increases.However, these studies did not account for quality of sleep. They used questionaries and interviews to estimate about how long each person slept.

What about those who think they are asleep for a long time but suffer from sleep apnea and are not truly in deep sleep for most of the night? Many other reasons why some could ‘sleep’ for a long time but not have truly restorative sleep. A recent study looked at the association between sleep restfulness + how long were people actually asleep and all-cause mortality. They measured sleep duration with an actual sleep study (polysomnography), which is much more accurate than interviews and questionaries. Essentially, the authors found that sleep duration really wasn’t the major factor, rather it was the quality of sleep plus duration. As sleep duration increased all cause mortality decreased. To most of us this is kind of obvious.

Be sure that you are getting quality sleep and feel restored in the morning. If you are sleeping for a long duration but still feel tired and not restored in the morning than you may have some sleep disorder, like sleep apnea and you should discuss this with your doctor.