Low-Fat Dietary Pattern Intervention and Health-Related Quality of Life: The Women's Health Initiative Randomized Controlled Dietary Modification Trial

Abstract

Background: Intensive dietary intervention programs may lead to benefits in vitality and other components of health quality. The Women's Health Initiative Dietary Modification (DM) intervention includes a large randomized controlled trial of an intensive intervention.

Objective: To evaluate whether the intervention is associated with improved health-related quality of life (HRQoL) subscales, overall self-reported health, depression symptoms, cognitive functioning, and sleep quality.

Design: This randomized controlled trial was analyzed as intent to treat.

Participants: Between 1993 and 1998, 48,835 women aged 50 to 79 years were recruited by 40 clinical centers across the United States. Eligibility included having fat intake at baseline ≥32% of total calories, and excluded women with any prior colorectal or breast cancer, recent other cancers, type 1 diabetes, or medical conditions with predicted survival <3 years.

Intervention: Goals were to reduce calories from fat to 20%, increase vegetables and fruit to 5+ servings, and increase grain servings to 6+ servings a day. During the first year, 18 group sessions were held, with quarterly sessions thereafter.

Main outcome measures: The RAND 36-Item Health Survey was used to assess HRQoL at baseline, Year 1, and close-out (about 8 years postrandomization), and estimate differential HRQoL subscale change scores.

Statistical analyses performed: Mean change in HRQoL scores (Year 1 minus baseline) were compared by randomization group using linear models.

Results: At 1 year, there was a differential change between intervention and comparison group of 1.7 units (95% CI 1.5, 2.0) in general health associated with the intervention. DM intervention improved physical functioning by 2.0 units (95% CI 1.7, 2.3), vitality by 1.9 units (95% CI 1.6, 2.2), and global quality of life by 0.09 units (95% CI 0.07, 0.12). With the exception of global quality of life, these effects were significantly modified by body mass index at baseline.

Conclusions: DM intervention was associated with small, but significant improvements in three HRQoL subscales: general health, physical functioning, and vitality at 1 year follow-up, with the largest improvements seen in the women with the greatest baseline body mass index.

Trial registration: ClinicalTrials.gov NCT00000611.

Keywords: Body mass index; Dietary intervention; Health-related-quality of life; Postmenopausal; Randomized controlled trial.

Copyright © 2016 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Histograms of change scores (year 1 minus baseline) for select quality of life scores by randomization assignment in the Women’s Health Initiative Dietary Modification Trial.

Figure 2. close–out (minus baseline), and the corresponding Effect Size for Health Related Quality of Life Scores in the Women’s Health Initiative Dietary Modification Trial

a Effect size is the estimated mean difference at year 1 or close–out, divided by the respective root–mean–square error. For all measures, the sign of the effect size has been flipped (if necessary) so that adverse effects (favors comparison) extend to the right and favorable effects (favors intervention) extend to the left.