Intro

Healthcare and research has continually uplifted the habit of sleeping, but it can sometimes be disadvantageous, especially when one sleeps too long. Based on the studies used in this article, oversleeping is defined as adults sleeping for an average of at least 9-10 hours a day. 

Physical Consequences

Although it’s been long supported by research that obesity and diabetes are linked to sleep deprivation, the same also goes for an excessive amount of rest. According to a nationally representative survey that analyzed sleeping habits of French adults, statistical analysis reported a strong correlation between longer amounts of sleep and increased risk of diabetes/obesity. Research regarding the reasons as to why this association exists is not as strong, but a more recent study seeks to examine the possible mechanisms that may explain the connection. 

From the recent study mentioned above, we see an image that illustrates some of the potential means by which excessive sleep can result in T2DM, or Type II diabetes mellitus, as well as obesity. For example, one possible pathway that is shown in the visual is that long sleep duration may lead to less physical activity, which can then lead to an increase in food intake. This thus can result in obesity or Type II diabetes mellitus.

Note: Type II diabetes mellitus is also known as adult-onset diabetes or just Type II diabetes. 

Figure 2. Tan, et al., “Association between long sleep duration and increased risk of obesity and type 2 diabetes: A review of possible mechanisms,” https://www.sciencedirect.com/science/article/pii/S1087079217300916#fig1, Date Accessed: 08/15/2022

Another image, shown above, presented by the same study more closely analyzes the effect of light exposure and circadian rhythms upon the likelihood of developing T2DM or obesity. When looking at the diagram above, we see that there is a smaller white range representing long-duration (LS) sleepers for natural light exposure, as well as a bigger white range for artificial light exposure. This aligns with the flowchart below, which demonstrates how reduced daytime exposure to sunlight and increased artificial light exposure would eventually result in increased risk of obesity/Type II diabetes. 

Note: LS represents those who are long-duration sleepers and NS represents those who are normal-duration sleepers. 

Psychological Consequences 

Not only does the tendency to sleep for an immoderate time result in physical detrimental consequences but also psychological ones as well. Based on a meta-analysis that involved over 20,000 participants for long sleep duration, the relative risk (with a 95% confidence interval) discovered for depression was 1.42. A relative risk determines how likely the risk is going to occur for a specific group compared to that same event happening for another group. As such, it’s 42% more likely for those who sleep a longer amount of time to develop depression, compared to the rest of the population.

Dong, et al., “Association between sleep duration and depression in US adults: A cross-sectional study,” https://www.sciencedirect.com/science/article/pii/S016503272101034X#tbl0002, Date Accessed: 08/15/2022

The figure above uses the reference number of hours (7-9) to portray the association between sleep duration and depression according to a multiple regression model. The resulting plot shows a negative correlation between sleep duration and depression BEFORE 8 hours and then a positive one AFTER 8 hours. For a negative correlation, this means that the less that you sleep (less than 8 hours), the stronger the association is with developing depression. For a positive correlation, this means that the more that you sleep (more than 8 hours), the greater the connection is with developing depression.

Note: OR stands for odds ratio, quantifying the strength of the association between sleep duration and depression.

Fatal Consequences

While there needs to be more research, a study that did quantitative analyses proved that there is an increased risk of mortality for long sleepers. Plausible links could include long sleepers having a shorter photoperiod (ratio of daylight to darkness), as well as changes in cytokine (important proteins) levels, which could all influence risk of mortality. Nevertheless, there is not enough evidence yet to conclude that long sleep duration is directly related to an increased risk of mortality.

Conclusion

It is evident that there still needs to be more work done to better examine the possible factors that could influence the probability of these physical, psychological, and fatal implications occurring. However, studies have demonstrated that there is some connection between long sleep and these negative effects. Overall, sleep is a tool for your body to get rest; nonetheless, balance is key.