Key points Ask Are physical activity of varying intensity and duration and time spent in sedentary behavior associated with the risk of incident stroke in middle-aged and older US adults? Findings In this cohort study of 7,607 adults, greater accumulation of light-intensity and moderate-to-vigorous-intensity physical activity was associated with a reduced risk of stroke. Spending more sedentary time and longer periods of sedentary time were associated with an increased risk of stroke. Meaning The findings of this study suggest that more time spent in physical activity, especially at moderate intensities, and less sedentary time, particularly over longer periods, may help reduce the risk of stroke. |
Importance
The amount and intensity of physical activity required to prevent stroke have not yet been fully determined due to previous reliance on self-report measures. Furthermore, the association between objectively measured time spent sedentary as an independent risk factor for stroke is unknown.
Aim
To investigate the associations of accelerometer-measured sedentary time and physical activity of varying intensity and duration with the risk of incident stroke.
Design, environment and participants
This cohort study involved participants who enrolled in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study from February 5, 2003 to October 30, 2007.
Accelerometer data were collected from 7,607 black and white adults aged 45 years and older in the contiguous US between May 12, 2009 and January 5, 2013. Data on other races and ethnicities were not collected for scientific reasons and clinics. By design, Black adults and residents of the Southeastern US were oversampled. Data were analyzed from May 5, 2020, to November 11, 2021.
Exhibitions
Sedentary time, light-intensity physical activity (LIPA), and moderate-to-vigorous-intensity physical activity (MVPA) were measured using a hip-mounted accelerometer worn for 7 consecutive days and stratified by tertile for analyses.
Main results and measures
Incident stroke.
Results
Among 7607 participants , the mean (SD) age was 63.4 (8.5) years; 4145 participants (54.5%) were women, 2407 (31.6%) were black, and 5200 (68.4%) were white. A total of 2523 participants (33.2%) resided in the stroke belt and 1638 (21.5%) resided in the stroke buckle.
During a mean (SD) of 7.4 (2.5) years of follow-up, 286 cases of incident strokes occurred (244 ischemic [85.3%]).
Fully adjusted hazard ratios (HRs) for incident stroke in the highest tertile compared with the lowest tertile were 0.74 (95% CI, 0.53-1.04; P = 0.08 ) for LIPA and 0.57 (95% CI, 0.38-0.84; P = .004) for MVPA.
Greater sedentary time was associated with a 44% increased risk of incident stroke (HR, 1.44; 95% CI, 0.99-2.07; P = .04). When comparing the highest with the lowest tertile, mean duration of sedentary bout was associated with a significantly increased risk of incident stroke (HR, 1.53; 95% CI, 1.10-2.12; P = 0.008).
After adjustment for sedentary time, the highest tertile of non-bout MVPA (shorter bouts [1-9 minutes]) was associated with a significantly lower risk of incident stroke compared to the lowest tertile (HR, 0. 62; 95% CI, 0.41-0.94; p = 0.02); however, bout-based MVPA (longer sets [at least 10 minutes]) was not (HR, 0.78; 95% CI, 0.53-1.15; P = 0.17).
When expressed as continuous variables , sedentary time was positively associated with the risk of incident stroke (HR per 1 hour/day increase in sedentary time: 1.14; 95% CI, 1.02-1.28 ; P = 0.02), and LIPA was negatively associated with the risk of incident stroke (HR per 1-hour/day increase in LIPA: 0.86; 95% CI, 0.77-0.97; P = 0.02).
Figure: Dose-response association of physical activity and sedentary time with risk of stroke. Models were adjusted for age, race, sex, region of residence, educational level, season of accelerometer use, current smoking, alcohol consumption, atrial fibrillation, left ventricular hypertrophy, history of coronary heart disease, and moderate to moderate intensity. vigorous physical activity for models testing sedentary time and light intensity physical activity or sedentary time for models testing moderate to vigorous intensity physical activity. Dark blue lines represent hazard ratios and shaded areas represent 95% CIs. A, Data were fitted using a nonlinear model (P= .15 for nonlinear association). The cubic polynomials were fitted with constraints placed on the resulting curve to ensure a smooth appearance using 3 nodes placed at the 5th, 20th, and 70th percentiles. The referent was the approximate median of the lowest tertile (0 minutes/day). B, Data were fitted using a linear model (P = 0.01). The reference was the approximate median of the lowest tertile (2.0 hours/day). C, Data were fitted using a linear model (P = 0.01). The reference was the approximate median of the lowest tertile (11.0 hours/16-hour day).
Conclusions and relevance
In this cohort study, objectively measured LIPA, MVPA, and sedentary time were significantly and independently associated with the risk of incident stroke. Longer duration of sedentary period was also independently associated with increased risk of incident stroke.
These findings suggest that replacing sedentary time with light intensity physical activity (LIPA), or even very short bouts of moderate to vigorous intensity physical activity (MVPA), may reduce the risk of stroke, supporting the concept of moving more and sitting less as a beneficial stroke risk reduction strategy among adults.
