How Long Should We Sleep?

Sleeping too little

A survey concluded that 34.8% of the US adults sleep less than 7 hours, the minimum recommended hour of sleep for adults from 18 to 60 years old by the Centers for Disease Control and Prevention (CDC).

Do you agree that  6-7 hours of sleep or even less is enough for you? If you agreed, you might be among the one-third population that is short on sleep. Short sleepers are relatively rare; in most cases, you are having inadequate sleep without even noticing it.

You wake up  early even on the weekends when you can sleep a bit longer. Your body’s circadian clock (biological clock) adjusts to the time you sleep and get up most days.

If this sounds like you, here is what you can do to reseat your circadian clock. Don’t set an alarm on your days off and sleep till you can. You will eventually find your natural sleep-wake cycle and get adequate sleep.

You may not feel any serious side effects of sleeping less other than tiredness. However, in the long-term, sleep deprivation can lead to a series of  health problems. One of the major health risks of sleep deprivation is cardiovascular disease. A study analyzed self-reported data from 32,152 participants in the National Health and Nutrition Examination Survey (NHANES) and found that sleeping less than 7 hours is associated with a higher risk of heart failure.1

When we fall asleep at night, our blood pressure decreases by 10-20%. But the blood pressure in people with sleep deprivation or poor sleep quality will not drop at night. Elevated night-time blood pressure is closely related to hypertension and a higher risk of stroke and heart attack.3 In another article “What do we do when we sleep”, we introduced the four stages of sleep.

During non-REM sleep stages, the heart rate drops and the heart has reduced stress and activity, while at the REM stage, the heart rate rises again. Overall, the change in heart activity during sleep has a regular and balanced pattern. But when we lack enough sleep, this regular pattern is disrupted, and this could increase the risk of heart attack by 20%.1

Excessive sleeping

So does it mean that we should sleep as much as we want?

In short, no. Excessive sleep is as dangerous as sleep deprivation. It is even a more serious problem than sleep deprivation because people tend to link sleep deprivation to negative health impacts, but few are aware of the health risks brought by excessive sleep.

Abundant evidence suggested that both insufficient and excessive sleep duration are linked to an increased risk for cardiovascular disease. Moreover, sleep duration in excess of 9 hours per night, as sleeping too little, is associated with a greater prevalence of stroke and heart failure.1

In fact, in many cases, excessive sleep is not the cause of cardiovascular disease, but the resulting symptom of other health or lifestyle problems. These health or lifestyle problems can in turn have a negative effect on our heart health.

One of the most common causes of excessive sleep is sleep apnea, a breathing disorder that causes brief pauses in breathing during sleep4. The direct cause of sleep apnea is that your airway is too narrow for you to breathe properly while you are sleeping.

Obesity, enlarged tonsils, drinking alcohol and smoking are found to be contributing factors of sleep apnea. Sleeping on your back may also increase the risk of sleep apnea. Other lifestyle factors such as working shift work (especially night shifts) breaks your natural circadian rhythm and make you feel tired all the time and want to sleep longer.

As you can see, lifestyle choices like shift work, obesity, alcohol and smoking are the real reasons why you might have excessive sleep at night. It’s primarily these factors rather than not getting enough sleep that increase the risk of developing cardiovascular disease.

So how long should we be sleeping?

It is recommended that adults should have 7 to 9 hours of sleep every day. As mentioned before, if you truly are a short sleeper, then 6 is also fine! But always be careful because if sleep deprivation becomes a habit, it might deceive you into thinking you are a short sleeper. 

If you are sure that you don’t have any other health conditions or lifestyle/environmental factors that make you sleep 10 or more hours a day, then it’s totally fine to follow your natural sleep-wake upcycle. 7 to 9 hours is a standard for most people but it’s best if you find your body’s own ideal sleep schedule. 

We spend one-third of our life sleeping and it is definitely one of the most important things in our life. It’s never too late to change your lifestyle and develop a good sleeping habit.

This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Adina Zhao

Medical Bioscientist - Imperial College London Medical Bioscience BSc
Modules covered: Integrative Body Systems, Molecular and Cellular Biology, Chemistry of Biological Interactions.
Past projects: Investigation of the influence of amino acid mutations of in-cluster gene lmbU on LmbU protein transcription and translation efficiency in Streptomyces lincolnensis, Investigation of the influence of red fluorescence protein mCherry on the photosynthetic efficiency of Arabidopsis thaliana .

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