Dietary intervention favorably influences physical functioning: the Women's Health Initiative randomized Dietary Modification trial.

BACKGROUND: In the Women's Health Initiative Dietary Modification (WHI DM) randomized trial, the dietary intervention reduced breast cancer mortality by 21% (P = 0.02) and increased physical activity as well.

OBJECTIVE: Therefore, the aim was to examine whether these lifestyle changes attenuated age-related physical functioning decline.

DESIGN: In a randomized trial, the influence of 8-years of a low-fat dietary pattern intervention was examined through 20 years cumulative follow-up.

PARTICIPANTS: /setting; From 1993-1998, 48,835 postmenopausal women, ages 50-79 years with no prior breast cancer and negative baseline mammogram were randomized at 40 US clinical centers to dietary intervention or usual diet comparison groups (40/60). The intervention significantly reduced fat intake and increased vegetable, fruit, and grain intake.

MAIN OUTCOME MEASURES: In post hoc analyses, physical functioning, assessed using the RAND 36-Item Short Form Health Survey (SF-36), evaluated quality or limitations of 10 hierarchical physical activities. Longitudinal physical functioning, reported against a disability threshold (when assistance in daily activities is required) was the primary study outcome.

STATISTICAL ANALYSES PERFORMED: Semiparametric linear mixed effect models (LME) were used to contrast physical functioning trajectories by randomization groups.

RESULTS: Physical functioning score, assessed 495,317 times with 11.0 (median) assessments per participant, was significantly higher in the intervention versus comparison groups through 12-years cumulative follow-up (P = 0.001), representing a reduction in age-related functional decline. The intervention effect subsequently attenuated and did not delay time to the disability threshold. Among women in the dietary intervention versus comparison groups, aged 50-59 years, who were physically inactive at entry, a persistent, statistically significant, favorable influence on physical functioning with associated delay in crossing the disability threshold by approximately a year was seen (P-interaction = 0.007).

CONCLUSIONS: In the WHI DM randomized trial, a dietary intervention which significantly reduced breast cancer mortality also significantly reduced age-related functional decline through 12 years, which was attenuated with longer follow-up.