Accelerometer measured physical activity and the incidence of cardiovascular disease: Evidence from the UK Biobank cohort study

Author summary Why was this study done? There is an inverse association between self-reported physical activity (PA) and occurrence of cardiovascular disease (CVD). However, there is uncertainty about the strength of this association as self-reported questionnaires are subject to differential measurement error. Accelerometers are small lightweight motion sensors that are typically worn on the wrist. They more reliably measure PA status and thus could improve understanding of associations with CVD. What did the researchers do and find? We used data from 90,211 UK Biobank participants without prior CVD who agreed to wear an accelerometer to measure their PA status over 7 days. Higher levels of PA were associated with lower risk for CVD that was similar across total, moderate- and vigorous-intensity PA. What do these findings mean? Our findings suggest that individuals who engage in higher levels of PA have lower risk for CVD throughout the range of PA measured. The lowest risk for CVD in the UK Biobank cohort is seen at the highest level of PA, whether total, moderate-intensity, or vigorous-intensity. Background Higher levels of physical activity (PA) are associated with a lower risk of cardiovascular disease (CVD). However, uncertainty exists on whether the inverse relationship between PA and incidence of CVD is greater at the highest levels of PA. Past studies have mostly relied on self-reported evidence from questionnaire-based PA, which is crude and cannot capture all PA undertaken. We investigated the association between accelerometer-measured moderate, vigorous, and total PA and incident CVD. Methods and findings We obtained accelerometer-measured moderate-intensity and vigorous-intensity physical activities and total volume of PA, over a 7-day period in 2013-2015, for 90,211 participants without prior or concurrent CVD in the UK Biobank cohort. Participants in the lowest category of total PA smoked more, had higher body mass index and C-reactive protein, and were diagnosed with hypertension. PA was associated with 3,617 incident CVD cases during 440,004 person-years of follow-up (median (interquartile range [IQR]): 5.2 (1.2) years) using Cox regression models. We found a linear dose-response relationship for PA, whether measured as moderate-intensity, vigorous-intensity, or as total volume, with risk of incident of CVD. Hazard ratios (HRs) and 95% confidence intervals for increasing quarters of the PA distribution relative to the lowest fourth were for moderate-intensity PA: 0.71 (0.65, 0.77), 0.59 (0.54, 0.65), and 0.46 (0.41, 0.51); for vigorous-intensity PA: 0.70 (0.64, 0.77), 0.54 (0.49,0.59), and 0.41 (0.37,0.46); and for total volume of PA: 0.73 (0.67, 0.79), 0.63 (0.57, 0.69), and 0.47 (0.43, 0.52). We took account of potential confounders but unmeasured confounding remains a possibility, and while removal of early deaths did not affect the estimated HRs, we cannot completely dismiss the likelihood that reverse causality has contributed to the findings. Another possible limitation of this work is the quantification of PA intensity-levels based on methods validated in relatively small studies. Conclusions In this study, we found no evidence of a threshold for the inverse association between objectively measured moderate, vigorous, and total PA with CVD. Our findings suggest that PA is not only associated with lower risk for of CVD, but the greatest benefit is seen for those who are active at the highest level.

Automated summary

The study found that higher levels of physical activity are associated with a lower risk of cardiovascular disease, regardless of total, moderate-intensity, or vigorous-intensity physical activity. The greatest benefit is seen for individuals who are active at the highest level, suggesting no threshold for the inverse association between objectively measured physical activity and CVD.