Healthy diet attenuates the association between prolonged sitting and mortality risk among cancer survivors

Prolonged sitting is an independent risk for mortality among cancer survivors, but whether higher dietary quality (DQ) may attenuate the detrimental effects of prolonged sitting is unknown. Therefore, this study aimed to examine the associations of prolonged sitting and DQ with mortality among cancer survivors. This study analyzed 2734 adult cancer survivors from the National Health and Nutrition Examination Survey from 2007 to 2018. Survey-weighted Cox proportional hazard models were used to evaluate the independent and combined associations of sitting time and DQ with mortality among cancer survivors. Prolonged sitting time was associated with higher all-cause and noncancer mortality risks, whereas qualified dietary quality (HEI-2015 ≥ 60) was associated with lower risks of all-cause, cancer, and noncancer mortality. In joint analyses, compared with individuals who had qualified DQ and sitting time less than 8 h/ d, those with unqualified DQ and sitting ≥ 8 h/d had significantly higher mortality risks. The corresponding hazard ratios (HRs) were 2.141 (95% CI: 1.536–2.985) for all-cause mortality, 2.534 (95% CI: 1.442–4.454) for cancer mortality, and 2.028 (95% CI: 1.368–3.008) for noncancer mortality. In contrast, among survivors with qualified DQ, prolonged daily sitting (≥ 8 h/d) was not significantly associated with increased mortality. The HRs were 1.507 (95% CI: 0.939–2.417) for all-cause mortality, 2.051 (95% CI: 0.893–4.709) for cancer mortality, and 1.293 (95% CI: 0.732–2.284) for noncancer mortality. Qualified dietary quality (HEI ≥ 60) might attenuate the increased risk of mortality associated with prolonged sitting time among cancer survivors.