Table 3. Risk of Incident Stroke by Tertiles of Mean Sedentary Bout Duration and Bouted and Unbouted MVPA.
| Model | Hazard ratio (95% CI) | P value for trenda | ||
|---|---|---|---|---|
| Tertile 1 | Tertile 2 | Tertile 3 | ||
| Mean sedentary bout duration b | ||||
| Stroke, No./total No. | 62/2535 | 86/2536 | 138/2536 | NA |
| Unadjusted | 1 [Reference] | 1.23 (0.88-1.71) | 1.85 (1.36-2.52) | <.001 |
| Model 1c | 1 [Reference] | 1.22 (0.88-1.69) | 1.73 (1.26-2.37) | <.001 |
| Model 2d | 1 [Reference] | 1.20 (0.86-1.67) | 1.64 (1.19-2.25) | .001 |
| Model 3e | 1 [Reference] | 1.16 (0.83-1.62) | 1.53 (1.10-2.12) | .008 |
| Unbouted MVPA f | ||||
| Stroke, No./total No. | 144/2527 | 87/2542 | 55/2538 | NA |
| Unadjusted | 1 [Reference] | 0.65 (0.50-0.85) | 0.48 (0.35-0.67) | <.001 |
| Model 1c | 1 [Reference] | 0.66 (0.50-0.87) | 0.48 (0.34-0.68) | <.001 |
| Model 2d | 1 [Reference] | 0.69 (0.52-0.91) | 0.53 (0.38-0.76) | <.001 |
| Model 3e | 1 [Reference] | 0.74 (0.55-1.00) | 0.62 (0.41-0.94) | .02 |
| Bouted MVPA g | ||||
| Stroke, No./total No. | 208/4762 | 44/1425 | 34/1420 | NA |
| Unadjusted | 1 [Reference] | 0.73 (0.53-1.01) | 0.59 (0.41-0.85) | .002 |
| Model 1c | 1 [Reference] | 0.76 (0.54-1.05) | 0.64 (0.44-0.93) | .009 |
| Model 2d | 1 [Reference] | 0.81 (0.58-1.13) | 0.69 (0.47-1.01) | .04 |
| Model 3e | 1 [Reference] | 0.87 (0.62-1.22) | 0.78 (0.53-1.15) | .17 |
Abbreviations: MVPA, moderate- to vigorous-intensity physical activity; NA, not applicable.
P value from linear trend test when tertiles were treated as an ordinal variable in the Cox proportional hazards regression model.
Cutoff points for mean sedentary bout duration were less than 8.3 minutes/bout for tertile 1, at least 8.3 to less than 11.2 minutes/bout for tertile 2, and at least 11.2 minutes/bout for tertile 3.
Model 1 was adjusted for age, sex, race, region of residence (expressed as interaction with follow-up time), educational level, and season in which the accelerometer was worn.
Model 2 was adjusted for all covariates in model 1 plus current smoking, alcohol consumption, atrial fibrillation, left ventricular hypertrophy, and history of coronary heart disease.
Model 3 was adjusted for all covariates in model 2 plus MVPA (for sedentary time and light-intensity physical activity) or sedentary time (for MVPA).
Cutoff points for unbouted MVPA were less than 2.0 minutes/day for tertile 1, at least 2.0 to less than 7.8 minutes/day for tertile 2, and at least 7.8 minutes/day for tertile 3.
Cutoff points for bouted MVPA were 0 minutes/day for tertile 1, more than 0 to less than 10.1 minutes/day for tertile 2, and at least 10.1 minutes/day for tertile 3.