Physical activity, sedentary behavior, and cause-specific mortality in black and white adults in the Southern Community Cohort Study

Abstract

There is limited evidence demonstrating the benefits of physical activity with regard to mortality risk or the harms associated with sedentary behavior in black adults, so we examined the relationships between these health behaviors and cause-specific mortality in a prospective study that had a large proportion of black adults. Participants (40-79 years of age) enrolled in the Southern Community Cohort Study between 2002 and 2009 (n = 63,308) were prospectively followed over 6.4 years, and 3,613 and 1,394 deaths occurred in blacks and whites, respectively. Black adults who reported the highest overall physical activity level (≥32.3 metabolic equivalent-hours/day vs. <9.7 metabolic equivalent-hours/day) had lower risks of death from all causes (hazard ratio (HR) = 0.76. 95% confidence interval (CI): 0.69, 0.85), cardiovascular disease (HR = 0.81, 95% CI: 0.67, 0.98), and cancer (HR = 0.76, 95% CI: 0.62, 0.94). In whites, a higher physical activity level was associated with a lower risk of death from all causes (HR = 0.76, 95% CI: 0.64, 0.90) and cardiovascular disease (HR = 0.69, 95% CI: 0.49, 0.99) but not cancer (HR = 0.95, 95% CI: 0.67, 1.34). Spending more time being sedentary (>12 hours/day vs. <5.76 hours/day) was associated with a 20%-25% increased risk of all-cause mortality in blacks and whites. Blacks who reported the most time spent being sedentary (≥10.5 hours/day) and lowest level of physical activity (<12.6 metabolic equivalent-hours/day) had a greater risk of death (HR = 1.47, 95% CI: 1.25, 1.71). Our study provides evidence that suggests that health promotion efforts to increase physical activity level and decrease sedentary time could help reduce mortality risk in black adults.

Keywords: blacks; cancer; exercise; prevention; sedentary behavior.

Figure 1.

Association between slow and fast walking (metabolic equivalent (MET)-hours/day) and all-cause mortality in blacks and whites, Southern Community Cohort Study, 2002–2011. A) Slow walking in blacks (P_trend = 0.47); B) fast walking in blacks (P_trend < 0.01); C) slow walking in whites (P_trend = 0.26); and D) fast walking in whites (P_trend = 0.30). The model was adjusted for sex, source of enrollment (community health center or general population), educational level (<9 years, 9–11 years, high school, some college, or beyond college), household income (<$15,000, $15,000–$24,999, $25,000–$49,999, or ≥$50,000), cigarette smoking (never; former, <1 pack/day; former, ≥1 pack/day; current, <1 pack/day; or current, ≥1 pack/day), body mass index (weight (kg)/height (m)²; <18.5, 18.5–24.9, 25–29.9, 30.0–34.9, or ≥35.0), sleep duration (<7, 7–8, or ≥9 hours/day), diabetes (yes or no), employment status (yes or no), sedentary behavior (hours/day), and other types of physical activity (MET-hours/day). Examples of slow walking included “moving around, walking at work, walking the dog, or for light exercise.” Examples of fast walking included “climbing stairs, walking fast to go places, or for exercise.” Bars, 95% confidence intervals.

Figure 2.

Association between sedentary behavior (hours/day) and cardiovascular mortality in men and women by race, Southern Community Cohort Study, 2002–2011. A) Black men (P_trend = 0.30); B) white men (P_trend < 0.01); C) black women (P_trend = 0.12); and D) white women (P_trend = 0.32). The model was adjusted for sex, source of enrollment (community health center or general population), educational level (<9 years, 9–11 years, high school, some college, or beyond college), household income (<$15,000, $15,000–$24,999, $25,000–$49,999, or ≥$50,000), cigarette smoking (never; former, <1 pack/day; former, ≥1 pack/day; current, <1 pack/day; or current, ≥1 pack/day), body mass index (weight (kg)/height (m)²; <18.5, 18.5–24.9, 25–29.9, 30.0–34.9, or ≥35.0), sleep duration (<7, 7–8, or ≥9 hours/day), diabetes (yes or no), employment status (yes or no), and overall physical activity (quartiles). Bars, 95% confidence intervals.

Figure 3.

Association between television viewing (hours/day) and all-cause mortality in men and women by race, Southern Community Cohort Study, 2002–2011. A) Black men (P_trend < 0.01); B) white men (P_trend = 0.40); C) black women (P_trend < 0.01); and D) white women (P_trend < 0.01). The model was adjusted for sex, source of enrollment (community health center or general population), educational level (<9 years, 9–11 years, high school, some college, or beyond college), household income (<$15,000, $15,000–$24,999, $25,000–$49,999, or ≥$50,000), cigarette smoking (never; former, <1 pack/day; former, ≥1 pack/day; current, <1 pack/day; or current, ≥1 pack/day), body mass index (weight (kg)/height (m)²; <18.5, 18.5–24.9, 25–29.9, 30.0–34.9, or ≥35.0), sleep duration (<7, 7–8, or ≥9 hours/day), diabetes (yes or no), overall physical activity (continuous), and other types of sedentary behavior (continuous). Bars, 95% confidence intervals.

Figure 4.

Joint effects of physical activity and sedentary behavior on all-cause mortality risk in black participants, Southern Community Cohort Study, 2002–2011. Tertiles of sedentary behavior are shown. Open circle, <6.5 hours/day; gray circles, 6.5–1.4 hours/day; and black circles, ≥10.5 hours/day. The model was adjusted for sex, source of enrollment (community health center or general population), educational level (<9 years, 9–11 years, high school, some college, or beyond college), household income (<$15,000, $15,000–$24,999, $25,000–$49,999, or ≥$50,000), cigarette smoking (never; former, <1 pack/day; former, ≥1 pack/day; current, <1 pack/day; or current, ≥1 pack/day), body mass index (weight (kg)/height (m)²; <18.5, 18.5–24.9, 25–29.9, 30.0–34.9, or ≥35.0), sleep duration (<7, 7–8, or ≥9 hours/day), diabetes (yes or no), and employment status (yes or no). MET, metabolic equivalent. Bars, 95% confidence intervals.