Diurnal Patterns of Accelerometer-Measured Physical Activity and Sleep in Relation to Cancer Risk: Findings From a Nationally Representative Study.

Physical activity (PA) and sleep are modifiable lifestyle factors, yet their circadian patterns in relation to cancer risk remain unclear. This study investigated their independent and joint associations with cancer risk. We analyzed data from 9038 adults aged ≥ 20 years in the 2011-2014 National Health and Nutrition Examination Survey. Circadian patterns of PA and sleep were derived from accelerometer data using k-means clustering. Weighted logistic regression assessed their independent and joint associations with cancer risk. Diurnal patterns were identified as early-morning (n = 2981), midday (n = 3497), and late-afternoon (n = 2560) for PA, and as morning lark (n = 4851), night owl (n = 2949), and irregular (n = 1238) for sleep. After adjusting for confounders, the early-morning PA pattern was associated with a 26% lower cancer risk compared with the midday PA pattern (OR = 0.74, 95% CI: 0.61-0.90), while the combined early-morning PA and morning lark sleep pattern conferred an even stronger protective effect compared with the midday PA and morning lark sleep joint pattern, corresponding to a 31% reduction (OR = 0.69, 95% CI: 0.49-0.96). Stratified analyses indicated that the inverse association of the early-morning PA pattern with cancer risk was stronger in females. No significant associations were observed between diurnal patterns of sleep and the risk of cancer. This study demonstrates that an early-morning PA pattern is associated with reduced cancer risk, with synergistically enhanced effects when combined with a morning lark sleep chronotype.