On the morning of March 16, the Chinese Sleep Research Association announced the annual theme of World Sleep Day in Beijing, "healthy sleep for all". The "2023 White Paper on Chinese Residents' Sleep" released at the meeting showed that the overall sleep quality of Chinese residents is poor, with an average sleep time of 6.75 hours after midnight and an average number of 1.4 awakenings. This is far from the ideal sleep duration and quality.
In the field of medicine and health, "phenotypic age" , which is often used as a predictor of various diseases and a biomarker for evaluating aging, refers to a person's physiological age, determined by their physical characteristics and functions rather than their actual age.
Research shows that age based biomarkers can be used as reliable indicators for individuals suffering from certain health diseases, such as cardiovascular disease, type II diabetes, nervous system diseases and other chronic disease phenotypes, which can provide more accurate information than actual age or single markers (such as telomere). Although these studies provide some evidence for the relationship between sleep and age-related phenotypic changes, more research is still needed to fully understand this relationship.
A study conducted by the Tsinghua University team You et al. analyzed the sleep patterns of 48,762 American adults and the phenotypic age reflected by multiple biomarkers, and found an interesting inverted U-shaped relationship: 7 hours of sleep per day is the optimal "care product" for the human body, and too little or too much sleep time will accelerate the increase of phenotypic age. In addition, this study cleverly incorporated exercise into the scope of discussion, revealing the subtle but crucial relationship between exercise and sleep.
According to the data from NHANES, the research team investigated the trend of sleep duration and the relationship between sleep duration and phenotypic age. In different annual cycles, most people's sleep duration is 6-9 hours. Moreover, since the 2015-2016 cycle, the proportion of short sleep and very short sleep has shown a downward trend, while the proportion of long sleep has shown an upward trend.
When the researchers used the crude model and Model 1 to evaluate sleep duration as a continuous variable, they found no significant correlation between it and phenotypic age. However, in the fully adjusted model, there was a significant correlation between continuous sleep duration and phenotypic age (Model 2, p=0.031).
Compared with the normal sleep group, short sleep duration was positively correlated with phenotypic age in the crude model and model 1 (crude model, p=0.050; model 1, p<0.001; model 2, p = 0.570). In addition, the researchers also noticed that long sleep duration was also positively correlated with increased phenotypic age (crude model, p<0.001; model 1, p<0.001; model 2, p = 0.010).
The results of this study suggest that there is a positive correlation between healthy sleep quality and improved cognitive health, and that it reduces the risk of decreased longevity.
The researchers used a two-stage linear regression model to calculate the inflection point between sleep duration and log-based phenotypic age as 7 hours (Figure 4). The relationship between sleep duration and phenotypic age is inverted U-shaped, which suggests that: consistent with previous studies ("The optimal sleep duration is not '8 hours'! Nature Subsidiary: Sleeping for less than or more than 7 hours can accelerate the growth of phenotypic age!"), the optimal sleep duration for humans is 7 hours, and sleeping for less or more than 7 hours can accelerate the growth of phenotypic age.
The results of this study also reveal potential health-related factors, such as exercise participation, that may affect the relationship between sleep duration and phenotypic age, and have important implications for clinical practice and public health policy. Subgroup analysis examines the relationship between sleep duration and phenotypic age in different exercise levels groups (Figure 5a).
The results showed that in the group without exercise habits, extremely short sleep and long sleep were positively correlated with phenotypic age. However, in participants who exercised for more than 150 minutes per week, sleep duration was negatively correlated with phenotypic age.
Next, the researchers used the RCS model to further investigate the dose-response relationship between sleep duration and phenotypic age under different exercise activities. As shown in Figure 5b, the group with long sleep duration can benefit from regular exercise, while the group with short sleep duration and high exercise volume cannot benefit from regular exercise. Therefore, regular circadian rhythm and sufficient sleep can play a beneficial role in exercise for the body.
Sleep duration and stability of circadian rhythm have a significant impact on the level of the key hormone serum testosterone. Simply put, when sleep is insufficient or the biological clock is disrupted, the concentration of serum testosterone in the human body may decrease, which in turn affects various metabolic processes and physiological functions in the body. Previous studies have shown that short-term sleep deprivation can disrupt the internal oxidation-reduction balance of the body, reduce the content of circulating metabolites that help maintain health, and may cause epigenetic changes, which can affect the performance of various aspects of the body .
In addition, long-term extreme sleep time patterns (too short or too long) are believed to be associated with accelerated aging, which can be verified through changes at the cellular level, such as the observed shortening of telomere length, which is a biomarker of cellular aging. In summary, maintaining moderate sleep time and good sleep habits are crucial for maintaining normal hormone regulation, antioxidant systems, and slowing the aging process.
Today is World Sleep Day, and scientists have revealed the magic of 7 hours of sleep: it is like a magical code that slows down aging and improves health. Neither too long nor too short, only moderate sleep combined with regular exercise can truly rejuvenate the body. Starting tonight, let's adjust our lifestyle and try to achieve the ideal sleep time of 7 hours every night!
