Health Risks of Not Enough Sleep: Why Z’s Matter!


How often do you get a good night’s sleep and wake up feeling totally rested? It’s increasingly hard to disconnect from work and technology, and it just seems like there aren’t enough hours in the day to get everything done. As a result, sleep rarely makes our “to-do” list.

While many of us think 5-6 hours of sleep a night are enough, it is recommended that adults (for teens and sleep, read here) sleep 7-9 hours a night in order to be fully rested and functioning the next day. [1]

Did you know that not getting enough sleep can cause health problems beyond just feeling tired and worn out? Recent studies have found that lack of adequate sleep is related to weight gain, sexual problems, reduced concentration, mental health problems, cancerous tumors and even Alzheimer’s disease.

How Lack of Sleep Causes Weight Gain

Lack of sleep affects metabolism. Research shows that after four nights of 4.5 hours of sleep a night, the fat cells of the study’s seven participants “aged.”[2] Aged fat cells are less sensitive to insulin, making a person more likely to gain weight gain and develop diabetes. Does not getting enough sleep for several nights in a row age your fat cells permanently, or does it take weeks and years of poor sleep to create insulin resistance? The study didn’t answer that question but it’s one that researchers are interested in.

A 2013 study of 16 healthy men and women by Rachel Markwald and colleagues from the University of Colorado found that those who slept only 5 hours a night ate more carbohydrates and snacked more after dinner than those who slept 9 hours. [3] While the group who slept 5 hours a night burned more calories per day than the group who slept 9 hours, those who slept less ended up consuming more food and gained an average of 2 pounds during the two-week study.

If a week or two without sufficient sleep can throw off your metabolism and add pounds, what happens if you don’t get enough sleep for much longer? Researchers who followed the sleep patterns and weight gain of 68,183 women for over 16 years found that those sleeping 5 hours or less a night weighed on average 5.4 pounds more than those sleeping 7 hours a night.[4] The women who slept the least per night were the ones who put on weight the fastest.

While too little sleep seems to cause people to put on pounds, too much weight causes people to sleep poorly. Research shows that excess weight can lead to sleep apnea, the leading cause of daytime sleepiness.[5] Other symptoms include loud and chronic snoring, pauses in snoring, and chokes and gasps after the pauses. There are two kinds of sleep apnea: obstructive sleep apnea, caused by a blockage of soft tissue in a person’s airways, and central sleep apnea, which occurs when the brain fails to regulate a person’s breathing.

Researchers at the University of Wisconsin School of Medicine studied 690 randomly selected Wisconsin residents for breathing problems during sleep using electrodes that measure breathing patterns and changes in the body. The participants were weighed and their sleep was measured at the beginning of the study and then again four years later. The study found that participants whose weight increased by 10% were six times more likely to have been recently diagnosed with moderate to severe breathing problems during sleep, such as obstructive sleep apnea.[6]

How Sleep Deprivation Can Affect your Sex Life

Sleep apnea may also contribute to sexual problems, including erectile dysfunction in men and women’s loss of interest in sex.

A 2011 study in The Journal of Sexual Medicine by Marian Peterson and colleagues in Scandinavia compared 80 women with obstructive sleep apnea against 240 women without sleep apnea between the ages of 28 and 64. The study found that women with sleep apnea had significantly higher rates of sexual dysfunction.[7] A previous study published in the same journal looked at 401 men suspected of having sleep apnea and found that 69% of those confirmed as having sleep apnea also had erectile dysfunction. Only 34% of men without sleep apnea were unable to achieve or maintain an erection.[8]

Lack of Sleep and its Effect on Attention, Reaction Time, and Motor Function

Studies show that partial sleep deprivation increases a person’s reaction time and decreases alertness. Gregory Belenky and colleagues recruited 66 healthy participants to spend two weeks living in a laboratory. After 3 days of adapting to their new sleep environment, participants were randomly assigned to one of four sleep groups: 3 hours of time in bed, 5 hours of time in bed, 7 hours of time in bed, or 9 hours of time in bed each night.[9]

Participants took a test that measured their reaction time, requiring them to click a button every time a light appeared on a screen in front of them. The reaction time of those who were only allowed 3 hours to sleep grew a little bit worse every day during the seven days of restricted sleep. For those who were only given 5 or 7 hours to sleep, speed and lapse time worsened at the beginning of the week and then stayed at the same lower rate for the remainder of the week. For those who had 9 hours in bed each night, speed and lapse time remained the same over the course of the study.

During the last 3 nights of the study, participants were given the opportunity to recover—all were allowed 8 hours of time in bed a night. Once again, their reactions were measured. Participants from the 5 and 7 hour groups didn’t show any real recovery; their performance stayed the same as it was at the end of the 7 nights of restricted sleep!  The 3 hour group showed some improvement, but their performance on the tests ended up being about the same as that of the 5 and 7 hour groups. None of the groups were able to perform as well on the tests as they had before the sleep restriction began—even after 3 nights of 8 hours in bed! These findings suggest that the effects of sleep deprivation last longer than people would expect.

A 2006 study sponsored by the National Center on Sleep Disorders Research and the National Highway Traffic Safety Administration reported that too little sleep impairs a driver’s ability to focus on the road, leading to crashes and car accidents.[10] Not getting enough sleep slows reaction time, decreasing a person’s ability to avoid collisions. Sleepiness also decreases attention, causes delayed response, and decreases the accuracy of short term memory.

According to a report by the National Highway Traffic Safety Administration, 832 deaths and 30,000 driving-related injuries in 2009 were caused by crashes involving a drowsy driver.[11] These statistics vastly underestimate the problem—many more people are killed or injured by tired drivers than are reported. More than a quarter of drivers surveyed admitted to feeling in the past month “so sleepy that they had a hard time keeping their eyes open.”[12]

Sleep Deprivation is Connected to Changes in Mood and Mental Health

A University of Pennsylvania study found that getting only 4.5 hours of sleep a night had a significant effect on participants’ mood.[13] When participants were allowed only 4.5 hours of sleep a night for one week, they reported feeling more stressed, angry, sad, and mentally exhausted. After returning to a regular sleep schedule, participants reported a dramatic improvement in mood.

A 2010 study conducted at University of Sydney in Australia found a relationship between sleep deprivation and psychological distress in young adults ages 17 to 24.[14] Young adults who sleep less than recommended are more likely to feel distressed and have “low mood,” which includes symptoms of depression, hopelessness, and anxiety and can lead to more serious mental disorders. As with weight gain, it is hard to know if lack of sleep causes mood problems or if it is the mood problems themselves that prevent people from sleeping well.

Poor Sleep and Alzheimer’s Disease

A study published in 2013 concluded that there is a link between poor sleep and the presence of a molecule that leads to the formation of plaque in the brain, which is associated with Alzheimer disease.[15] Previous studies have shown that sleep problems, including unintentional napping and insomnia, are common in patients who already have Alzheimer disease.[16]

Researchers were curious if poor sleep patterns were present in the earliest stages of Alzheimer’s prior to any obvious symptoms of the disease.  They hypothesized that the presence of the molecule ß-amyloid (Aß) negatively affects sleep patterns and that poor sleep may make people more likely to develop ß-amyloid. The study included 142 cognitively normal participants ages 45 to 75. Researchers observed the participant’s sleep and wake cycles while also measuring Aß42 levels in their cerebrospinal fluid, an indicator of ß-amyloid. The results showed that the 32 men and women with ß -amyloid had worse sleep quality than those without ß-amyloid.  The researchers were not able to conclude whether poor sleep leads to ß-amyloid formation. More research is needed to fully understand the relationship between poor sleep or lack of sleep and Alzheimer’s disease.

Disrupted Sleep and Tumor Growth

A study done on mice, published in 2014, suggests that disrupted sleep makes cancerous tumors grow bigger and faster. The researchers looked at 2 groups of mice: One group of mice was allowed to sleep normally without being disturbed and the other group had their sleep disrupted by running a brush through the cage every 2 minutes to wake them up. After one week both groups of mice were injected with tumor cells. They found that both groups of mice got cancer but the mice with disrupted sleep had tumors that were twice as big and grew faster than the tumors in the mice that slept normally.

The researchers thought that disrupted sleep may lead to bigger and faster-growing tumors by over-stimulating a biological response that is similar to the immune response. When they genetically engineered mice to not have an over-stimulated biological response their tumors were the same size as the tumors in mice that slept normally. More research is needed to find out whether sleep disruption affects tumors in humans.[17]

Bottom Line

  • Although most adults deny it, adults require 7 to 9 hours of sleep a night to function at their best, so put “sleep” on your to-do list!
  • Getting a full night’s sleep most nights is essential to your health.  It helps you control your weight and keep your mind focused.
  • Sleep deprivation can have devastating short-term effects, like making you more prone injury and death from accidents, and is linked to a range of other health problems that can shorten your life, such as obesity and depression.
  • There are simple, proven ways to help you get to sleep faster, sleep longer, and wake up feeling more refreshed.  Sleeping pills are not included in that list.

All articles are reviewed and approved by Dr. Diana Zuckerman and other senior staff.

  1. “CDC Features.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 24 Apr. 2017, Accessed 17 Aug. 2017.
  2. Broussard J, Ehrmann D, Van Cauter E, Tasali E, Brady M. Impaired insulin signaling in human adipocytes after experimental sleep restriction: a randomized, crossover study. Annals of Internal Medicine. 2012:157(8):549-557.
  3. Markwald R, Melanson E, Smith M, et al. Impact of insufficient sleep on total daily energy expenditure, food intake and weight gain. Proceedings of the National Academy of Sciences of the United States of America. 2012;110(14):5695-5700.
  4. Patel S, Atul M, White P, Gottlieb D, Hu F. Association between reduced sleep and weight gain in women. American Journal of Epidemiology.2006:164(10):947-954.
  5.] People with sleep apnea stop breathing during sleep for at least 10 seconds at a time.[end
  6. Peppard PE, Young T, Palta M, Dempsey J, Skatrud J. Longitudinal study of moderate weight change and sleep-disordered breathing. JAMA. 2000 Dec 20;284(23):3015-21.
  7. Peterson M, Kristensen E, Berg S, Giraldi A, Midgren B. Sexual function in female patients with obstructive sleep apnea. Journal of Sexual Medicine. 2011:8(9):2560-2568.
  8. Budweiser S, Enderlein S, Jorres RA, et al. Sleep apnea is an independent correlate of erectile and sexual dysfunction. Journal of Sexual Medicine. 2009:6(11):3147-3157.
  9. Belenky G, Wesensten NJ, Thorne Dr, et al. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose response study. J Sleep Res. 2003:12(1):1-12.
  10. Drowsy driving and automobile crashes. National Highway Traffic Safety Administration. 2006.
  11. Traffic Safety Facts, Drowsy Driving. National Highway Traffic Safety Administration  (March 2011).
  12. The Prevalence and Impact of Drowsy Driving. AAA Foundation for Traffic Safety (November 2010).
  13. Dinges, D. et al., Cumulative sleepiness, mood disturbance, and psychomotor vigilance decrements during a week of sleep restricted to 4 – 5 hours per night, sleep. 1997 Apr; 20 (4): 267–277
  14. Glozier N, Martiniuk A, Patton G, et al. Short sleep duration in prevalent and persistent psychological distress in young adults: the drive study. SLEEP. 2010:33(09).
  16. McCurry, SM, Logsdon RG, Teri L, et al. Characteristics of sleep disturbance in community-dwelling Alzheimer’s disease patients. J Geruatr Psychiatry Neurol. 1999;12(2):53-59
  17. Hakim F, et al. Fragmented sleep accelerates tumor growth and progression through recruitment of tumor-associated macrophages and TLR4 signaling. Cancer research. 2014;74(5):1329-1337