Objective

To examine whether changes in diet quality predict changes in central adiposity among postmenopausal women.

Methods

At baseline and 3-year follow-up, Women's Health Initiative Observational Study participants completed food frequency questionnaires, and waist circumference was measured (WC, n = 67,175). In a subset, trunk fat was measured via dual-energy X-ray absorptiometry (DXA, n = 4,254). Using multivariable linear regression, 3-year changes in dietary patterns (Healthy Eating Index-2010, Alternate Healthy Eating Index-2010, Alternate Mediterranean Diet, and Dietary Approaches to Stop Hypertension) were examined as predictors of concurrent changes in WC and, secondarily, DXA.

Results

Mean (SD) age and 3-year changes in weight and WC were 63 (7) years, 0.52 (4.26) kg, and 0.94 (6.65) cm. A 10% increase in any dietary pattern score, representing improved diet quality, was associated with 0.07 to 0.43 cm smaller increase in WC over 3 years (all P < 0.05). After adjusting for weight change, associations attenuated to 0.02 to 0.10 cm but remained statistically significant for all patterns except Alternate Mediterranean Diet. Results were similar for DXA trunk fat.

Conclusions

Three-year improvements in diet quality are modestly protective against gain in WC and partially explained by lesser weight gain. Achieving and maintaining a healthful diet after menopause may protect against gains in central adiposity.

Background

Achieving a healthy weight is recommended for all breast cancer survivors. Previous research on postdiagnosis weight change and mortality had conflicting results.

Methods

We examined whether change in body weight in the 18 months following diagnosis is associated with overall and breast cancer-specific mortality in a cohort of n = 12,590 stage I-III breast cancer patients at Kaiser Permanente using multivariable-adjusted Cox regression models. Follow-up was from the date of the postdiagnosis weight at 18 months until death or June 2015 [median follow-up (range): 3 (0-9) years]. We divided follow-up into earlier (18-54 months) and later (>54 months) postdiagnosis periods.

Results

Mean (SD) age-at-diagnosis was 59 (11) years. A total of 980 women died, 503 from breast cancer. Most women maintained weight within 5% of diagnosis body weight; weight loss and gain were equally common at 19% each. Compared with weight maintenance, large losses (≥10%) were associated with worse survival, with HRs and 95% confidence intervals (CI) for all-cause death of 2.63 (2.12-3.26) earlier and 1.60 (1.14-2.25) later in follow-up. Modest losses (>5%-<10%) were associated with worse survival earlier [1.39 (1.11-1.74)] but not later in follow-up [0.77 (0.54-1.11)]. Weight gain was not related to survival. Results were similar for breast cancer-specific death.

Conclusion

Large postdiagnosis weight loss is associated with worse survival in both earlier and later postdiagnosis periods, independent of treatment and prognostic factors.

Impact

Weight loss and gain are equally common after breast cancer, and weight loss is a consistent marker of mortality risk. Cancer Epidemiol Biomarkers Prev; 26(1); 44-50. ©2016 AACR SEE ALL THE ARTICLES IN THIS CEBP FOCUS SECTION, "THE OBESITY PARADOX IN CANCER EVIDENCE AND NEW DIRECTIONS".

Background

There is widespread concern about the use of body mass index (BMI) to define obesity status in postmenopausal women because it may not accurately represent an individual's true obesity status. The objective of the present study is to examine and adjust for exposure misclassification bias from using an indirect measure of obesity (BMI) compared with a direct measure of obesity (percent body fat).

Methods

We used data from postmenopausal non-Hispanic black and non-Hispanic white women in the Women's Health Initiative (n=126,459). Within the Women's Health Initiative, a sample of 11,018 women were invited to participate in a sub-study involving dual-energy x-ray absorptiometry scans. We examined indices of validity comparing BMI-defined obesity (≥30 kg/m), with obesity defined by percent body fat. We then used probabilistic bias analysis models stratified by age and race to explore the effect of exposure misclassification on the obesity-mortality relationship.

Results

Validation analyses highlight that using a BMI cutpoint of 30 kg/m to define obesity in postmenopausal women is associated with poor validity. There were notable differences in sensitivity by age and race. Results from the stratified bias analysis demonstrated that failing to adjust for exposure misclassification bias results in attenuated estimates of the obesity-mortality relationship. For example, in non-Hispanic white women 50-59 years of age, the conventional risk difference was 0.017 (95% confidence interval = 0.01, 0.023) and the bias-adjusted risk difference was 0.035 (95% simulation interval = 0.028, 0.043).

Conclusions

These results demonstrate the importance of using quantitative bias analysis techniques to account for nondifferential exposure misclassification of BMI-defined obesity. See video abstract at, http://links.lww.com/EDE/B385.