Joint associations of accelero-meter measured physical activity and sedentary time with all-cause mortality: a harmonised meta-analysis in more than 44 000 middle-aged and older individuals

Abstract

Objectives: To examine the joint associations of accelerometer-measured physical activity and sedentary time with all-cause mortality.

Methods: We conducted a harmonised meta-analysis including nine prospective cohort studies from four countries. 44 370 men and women were followed for 4.0 to 14.5 years during which 3451 participants died (7.8% mortality rate). Associations between different combinations of moderate-to-vigorous intensity physical activity (MVPA) and sedentary time were analysed at study level using Cox proportional hazards regression analysis and summarised using random effects meta-analysis.

Results: Across cohorts, the average time spent sedentary ranged from 8.5 hours/day to 10.5 hours/day and 8 min/day to 35 min/day for MVPA. Compared with the referent group (highest physical activity/lowest sedentary time), the risk of death increased with lower levels of MVPA and greater amounts of sedentary time. Among those in the highest third of MVPA, the risk of death was not statistically different from the referent for those in the middle (16%; 95% CI 0.87% to 1.54%) and highest (40%; 95% CI 0.87% to 2.26%) thirds of sedentary time. Those in the lowest third of MVPA had a greater risk of death in all combinations with sedentary time; 65% (95% CI 1.25% to 2.19%), 65% (95% CI 1.24% to 2.21%) and 263% (95% CI 1.93% to 3.57%), respectively.

Conclusion: Higher sedentary time is associated with higher mortality in less active individuals when measured by accelerometry. About 30-40 min of MVPA per day attenuate the association between sedentary time and risk of death, which is lower than previous estimates from self-reported data.

Keywords: accelerometer; death; meta-analysis; sedentary.

Figure 1

The joint association between total physical activity and sedentary time and all-cause mortality. Analyses are adjusted for age, sex when applicable, socioeconomic position, BMI, smoking, presence of prevalent diseases or self-reported poor health, and other putative confounding factors displayed in online supplemental table 1, and additionally excluding deaths within 2 years (n=42 203; 2508 deaths). Data are HRs and 95% CIs. Sedentary time is expressed as percentage of daily wear time. The median amount of total physical activity (CPM), and time (min/day) spent sedentary across tertiles were 138 CPM, 251 CPM and 396 CPM; and 8.5, 9.4 and 10.7 hours/day, respectively (see online supplemental table 2 for additional information). BMI, body mass index; CPM, counts per minute.

Figure 2

The joint association between moderate-to-vigorous-intensity physical activity (MVPA) and sedentary time and all-cause mortality. Analyses are adjusted for age, sex when applicable, socioeconomic position, BMI, smoking, presence of prevalent diseases or self-reported poor health, other putative confounding factors displayed in online supplemental table 1, and additionally excluding deaths within 2 years (n=42 203; 2508 deaths). Data are HRs and 95% CIs. sedentary time and MVPA are expressed as percentage of daily wear time. The median amount of time (min/d) spent sedentary and in mvpA (min/day) across tertiles were 8.5, 9.5 and 10.7 hours/day; and 2.3, 11.2 and 34.3 min/day, respectively (see online supplemental table 2 for additional information). BMI, body mass index.

Figure 3

The joint association between moderate-to-vigorous-intensity physical activity (MVPA) and sedentary time (SED) and all-cause mortality categorised by national (A) and non-national cohorts (B). Data are adjusted for age, sex, BMI, socioeconomic position, smoking, presence of prevalent diseases or self-reported poor health and other putative confounding factors according to online supplemental table 1. Data are HRs and 95% CIs. Sedentary time and MVPA are expressed as percentage of daily wear time. The median amount of time (min/day) spent sedentary and in mvpA (min/day) across tertiles were 7.1, 8.6 and 10.2 hours/day; and 10.6, 27.0 and 52.2, min/day, respectively for the National cohorts (figure 3a) and 8.9, 10.1 and 11.3 hours/day; and 1.4, 9.5 and 29.7 min/day, respectively, for the non-national cohorts (figure 3B) (see online supplemental table 2 for additional information). BMI, body mass index.