Physical Activity Across Mid-Life and Mortality Outcomes in Australian Women: A Target Trial Emu

26 Mar 20264 min read0 viewsJournal Feed

GIST

by Binh Nguyen, Katherine B. Owen, Mengyun Luo, Wendy Brown, Gregore I.

Mielke, Philip J. Clare, Ding Ding Background Long-term causal evidence comparing different physical activity patterns and mortality outcomes is needed.

Using observational data to emulate an RCT, this study compared different physical activity patterns over 15 years in relation to mortality from all causes, cardiovascular disease (CVD) and cancer in mid-aged Australian women. Methods and findings A target trial emulation framework was used to emulate an RCT, based on data collected every 3 years (nine surveys between 1996 and 2019) from 11,169 women in the Australian Longitudinal Study on Women’s Health (ALSWH; 1946−51 cohort).

Two emulated interventions were compared against consistent non-adherence (control) to WHO moderate-to-vigorous physical activity (MVPA) recommendations during the 15-year ‘exposure period’: (1) consistent adherence to recommendations (at least 150 min/week) over 15 years (2001−2016; women were 50−55–65−70 years); and (2) starting to meet the recommendations at age 55, 60, or 65 years.

Clinical Editorial

Study design and objective

Aims to evaluate how distinct long-term physical activity patterns relate to mortality from all causes, cardiovascular disease (CVD), and cancer.
Employs a target trial emulation framework using longitudinal observational data to approximate a randomized controlled trial.
Analysis uses nine survey waves from 1996 to 2019 within the Australian Longitudinal Study on Women’s Health (ALSWH), focusing on the 1946–1951 birth cohort and 11,169 participants.

Exposure strategies and comparison

Two MVPA-based interventions were contrasted against persistent non-adherence to WHO guidelines (≥150 minutes per week).
Intervention 1: sustained adherence to recommended MVPA levels across the entire 15-year exposure window (2001–2016), with participants aged roughly 50–70 at follow-up.
Intervention 2: initiation of meeting MVPA recommendations at later life milestones (age 55, 60, or 65), to assess potential delayed uptake effects.
The reference (control) condition was consistent non-adherence over the same period.

Outcomes and data handling

Outcomes included mortality from all causes, CVD, and cancer, ascertained from national death registries for the period between survey 4 and survey 9 (ages approximately 53–58 to 68–73).
Analyses used marginal structural modeling to account for time-varying covariates and potential confounding, under assumptions of conditional exchangeability, positivity, consistency, and no interference.
Self-reported physical activity constituted the primary exposure measure, with acknowledgment of its limitations.

Key findings and interpretation

All-cause mortality: consistent adherence to MVPA recommendations showed a protective signal relative to persistent non-adherence, with a Bayes factor of 5.71 (RR ≈ 0.50; 99.5% CI 0.27–0.94; RD ≈ −5.2%).
CVD mortality: the evidence suggested a potential protective direction (RR ≈ 0.50; 99.5% CI 0.19–1.30; RD ≈ −2.1%), but results were characterized by greater statistical uncertainty (BF ≈ 2.05; wide interval crossing unity).
Cancer mortality: suggested protective direction (RR ≈ 0.35; 99.5% CI 0.10–1.17; RD ≈ −3.3%), yet with notable uncertainty (BF ≈ 2.26; CI spanning unity).
Initiation of MVPA in mid-life (at 55, 60, or 65) yielded less certain effects across mortality outcomes.

Context and limitations

The authors emphasize uncertainty around several estimates, particularly for CVD and cancer mortality, due to wide confidence intervals and Bayes factors not decisively favoring effects.
A primary limitation is reliance on self-reported physical activity, which may introduce measurement error.
Generalizability may be limited to mid-aged Australian women within the ALSWH cohort, and findings may not extend to all populations.