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.