“Move more, sit less” is a feasible and impactful guideline for improving cancer survival

To date, there is consistent and compelling evidence that highest vs lowest levels of physical activity (PA) are associated with a 30%-45% reduction in mortality for breast, colon, and prostate cancer patients (1,2). Although research in recent years has gained considerable momentum, several critical gaps in knowledge remain (3). Notably, limited epidemiological data are available to confirm survival advantages for other cancer types or to conclude that PA improves disease-free survival, treatment efficacy, treatment completion rates, or common treatment-related side effects including cardiotoxicity, chemotherapy-induced peripheral neuropathy, cancer-related cognitive impairment, nausea, or pain (1,2,4-6). Additional questions regarding underlying biological mechanisms linking PA with improved survival and the frequency, intensity, duration, and type of PA needed to optimize cancer outcomes remain unanswered (7). An important limitation of the current body of evidence includes reliance on self-report PA data collected at one timepoint, which could be prone to measurement error, misclassification, and bias (8,9). For example, if self-report PA only represents an exposure window in the peridiagnosis period, a reverse causation bias could ensue if participants with more symptomatic disease also decreased their usual PA (8,9). Conversely, for some patients, a cancer diagnosis is a teachable moment, and thus, PA collected at study enrollment may not accurately reflect increases in PA that occur after treatment completion and throughout follow-up (8,9). Indeed, recent evidence from a study of breast cancer survivors before, during, and after treatment showed the prevalence of patients meeting the PA guidelines drastically decreased during chemotherapy but returned to prediagnosis levels approximately 2 years after treatment completion (10). Although highly feasible, reliance on self-report PA questionnaires may introduce bias caused by systematic underor overreporting according to PA type or intensity (11,12). For example, in older adults, only 10%-20% of the variability in device-measured activity can be attributed to self-report activity (13,14). This may be partly owing to the fact that the current PA guidelines emphasize moderate-to-vigorous intensity recreational PA (MVPA) (4), thus many questionnaires may not capture other domains and intensities of activity or sedentary behavior. As the body of literature informing our understanding of the associations of PA and sedentary behavior with cancer survival continues to progress, experts have cautioned the scientific community to consider several methodological issues when designing new studies (2), namely, that the existing body of observational research would greatly benefit from the addition of objective assessments of sedentary time and all domains and intensities of PA at multiple timepoints throughout cancer survivorship (2). In this issue of the Journal, Salerno et al. (15) answers this call by leveraging accelerometry-derived data from a representative sample of cancer survivors in the United States to examine associations of sedentary behavior, light-intensity PA, MVPA, and total PA with all-cause mortality. The study population included 480 adults enrolled in the 2003-2004 and 2005-2006 cycles of the National Health and Nutrition Examination Survey. Participants self-reported age at diagnosis for up to 4 primary cancers, agreed to wear an Actigraph accelerometer on the nondominant hip during all waking hours for a 7-day period, and were followed for subsequent mortality for an average of 12 years through 2015 (15). To be considered in the analyses, accelerometer wear time needed to include at least 10 hours of monitoring per day for at least 1 day (15). Sedentary time was quantified as hours per day spent below 100 counts per minute (cpm); lightintensity PA was quantified as hours per day between 100 and 759 cpm; MVPA was quantified as hours per day spent at or above 760 cpm; and total PA was quantified as hours per day spent at or above 100 cpm (15). In multivariable analyses, each exposure of interest was modeled as a categorical variable according to quartiles of activity and as a continuous variable according to 1-hour increments of activity. Results of multivariable analyses revealed that highest vs lowest quartiles of total PA and MVPA were associated with a striking 67% and 69% reduction in all-cause mortality, respectively (15). Interestingly, the highest vs lowest quartile of light-intensity PA was also associated with a 63% reduction in mortality—and the association between light-intensity PA and mortality was robust to adjustment for MVPA (15). Salerno et al. (15) also reported a 32% and 37% reduction in mortality for every 1-hour increase in total and MVPA, respectively, and a remarkable 49% decrease in mortality for every 1-hour increase in light-intensity PA. Again, the association of light-intensity PA with decreased mortality