| To investigate the associations of weight cycling and non-insulin dependent diabetes mellitus (NIDDM) with the risk of invasive postmenopausal breast cancer, a nested case-control study was conducted using Kaiser Permanente Southern California (KPSC) outpatient medical records. A total of 24,901 weight measurements spanning two-decade study periods were abstracted from outpatient medical records for 291 cases and 339 controls. For multivariable analysis, the Quetelet's Body Mass Index (BMI) was used to have a height-independent measure. Simple linear regressions were run for each participant with BMI as the independent variable with number of days from the beginning of the study period as the dependent variable. The magnitude of BMI cycling for each participant was estimated by the root-mean-square error from the linear regression, persistent BMI gains-or-losses were computed from the slope and the intercept served as an estimate of the initial BMI at the beginning of the study period. The study found that for women whose gained BMI over the study period , the highest quartile of BMI cycling magnitude was associated with reduced risk for postmenopausal breast cancer when compared to the lower three quartiles (adjusted OR=0.43, 95% CI: 0.26-0.72) and for these same gainers NIDDM was associated with increased risk of postmenopausal breast cancer, after taking into account the effect modification for a diagnosis of NIDDM with gaining BMI versus losing BMI (adjusted OR=3.12, 95% CI: 1.59-6.10). However, neither of these associations was seen for women who lost BMI. These findings potentially provide new directions for non-invasive interventions to reduce risk of invasive postmenopausal breast cancer. |
