Prospective evaluation of dietary and lifestyle pattern indices with risk of colorectal cancer in a cohort of younger women.

BACKGROUND: Although colorectal cancer (CRC) incidence in the USA is declining overall, its incidence is increasing among those younger than 50 years of age. The reasons underlying the increasing trend are largely unknown, although behavioral changes, such as unhealthy diet and lifestyle factors, may be partially responsible. DESIGN: A prospective cohort study included 94 217 women aged 26-45 years at baseline. Validated anthropometric measures and lifestyle information were self-reported biennially. Exposures were four recommendation-based dietary indices-the prime diet quality score and three plant-based dietary indices; and two mechanism-based indices-the empirical dietary and lifestyle index for hyperinsulinemia (EDIH and ELIH). We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) for overall CRC and for early-onset (before age 50) and after age 50 CRC separately. RESULTS: We documented 332 cases of CRC during 24 years of follow-up (2 113 655 person-years), with an average age of 52 ± 7 years at diagnosis. Hyperinsulinemic dietary and lifestyle patterns were associated with a higher risk of CRC. Multivariable-adjusted HRs (95% CIs) comparing participants in the highest versus lowest quartile were: 1.67 for EDIH (95% CI: 1.15-2.44, P-trend = 0.01) and 1.51 for ELIH (95% CI: 1.10-2.08, P-trend = 0.01). Moreover, per 75% increment in rank, ELIH appeared to be a stronger risk factor for early-onset CRC (HR = 1.86, 95% CI: 1.12-3.07) than after age 50 CRC (HR = 1.20, 95% CI: 0.83-1.73, P-heterogeneity = 0.16). The four recommendation-based indices were not significantly associated with overall, early-onset, or after age 50 CRC risk (per 75% increment in rank, HRs ranged from 0.75 to 1.28). CONCLUSION: Dietary and lifestyle patterns contributing to hyperinsulinemia were associated with greater CRC risk in younger women. Moreover, the hyperinsulinemic lifestyle showed a suggestively stronger positive association with early-onset CRC risk, compared with after age 50 CRC. Our findings suggest that dietary and lifestyle interventions to reduce insulinemic potential may be effective for CRC prevention among younger women.

Longitudinal changes in the dietary inflammatory index: an assessment of the inflammatory potential of diet over time in postmenopausal women.

BACKGROUND/OBJECTIVES: The dietary inflammatory index (DII) measured at one time point is associated with risk of several chronic diseases, but disease risk may change with longitudinal changes in DII scores. Data are lacking regarding changes in DII scores over time; therefore, we assessed changes in the DII in the Women's Health Initiative (WHI). SUBJECTS/METHODS: DII scores were calculated using data from repeated food frequency questionnaires in the WHI Observational Study (OS; n=76 671) at baseline and year 3, and the WHI Dietary Modification trial (DM; n=48482) at three time points. Lower DII scores represent more anti-inflammatory diets. We used generalized estimating equations to compare mean changes in DII over time, adjusting for multiple comparisons, and multivariable-adjusted linear regression analyses to determine predictors of DII change. RESULTS: In the OS, mean DII decreased modestly from -1.14 at baseline to -1.50 at year 3. In the DM, DII was -1.32 in year 1, -1.60 in year 3 and -1.48 in year 6 in the intervention arm and was -0.65 in year 1, -0.94 in year 3 and -0.96 in year 6 in the control arm. These changes were modified by body mass index, education and race/ethnicity. A prediction model explained 22% of the variance in the change in DII scores in the OS. CONCLUSIONS: In this prospective investigation of postmenopausal women, reported dietary inflammatory potential decreased modestly over time. Largest reductions were observed in normal-weight, highly educated women. Future research is warranted to examine whether reductions in DII are associated with decreased chronic disease risk.