While sleep duration has traditionally dominated public health discussions, this study shifts the spotlight to sleep regularity including bedtime consistency and circadian rhythm stability as a critical but underappreciated factor in long-term health outcomes.
The researchers used actigraphy a method of objectively measuring movement and sleep to track participants’ sleep over an average period of 6.8 years. The data were then cross-referenced with clinical records to examine associations with disease risk. Results showed that 92 diseases had over 20% of their risk attributable to poor sleep behavior. Notably, people with an irregular bedtime after 12:30 a.m. were found to have a 2.57-fold higher risk of liver cirrhosis. Additionally, low interdaily stability a measure of circadian rhythm consistency increased the risk of gangrene by 2.61 times.
The study also challenges long-standing assumptions about “long sleep” (defined as nine hours or more). While earlier studies based on self-reports linked long sleep to heart disease and stroke, the objective data here showed such an association with only one disease. Misreporting may explain the discrepancy: 21.67% of long sleepers actually slept less than six hours, confusing time spent in bed with actual sleep time.
"Our findings underscore the overlooked importance of sleep regularity," said Prof. Shengfeng Wang, senior author of the study. "It's time we broaden our definition of good sleep beyond just duration."
Reference: imeng Wang, Qiaorui Wen, Siwen Luo, Lijuan Tang, Siyan Zhan, Jia Cao, Shengfeng Wang, Qing Chen. Phenome-wide Analysis of Diseases in Relation to Objectively Measured Sleep Traits and Comparison with Subjective Sleep Traits in 88,461 Adults. Health Data Science, 2025; 5 DOI: 10.34133/hds.0161
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