Trabecular Bone Score Declines During the Menopause Transition: The Study of Women's Health Across the Nation (SWAN)

Abstract

Context: Rapid bone density loss starts during the menopause transition (MT). Whether other components of bone strength deteriorate before the final menstrual period (FMP) remains uncertain.

Objective: To discern whether trabecular bone score (TBS) declines during the MT.

Design: An 18-year longitudinal analysis from the Study of Women's Health Across Nation.

Setting: Community-based cohort.

Participants: A total of 243 black, 164 Japanese, and 298 white, initially pre- or early perimenopausal women, who experienced their FMP.

Main outcome measures: TBS, an indicator of bone strength.

Results: Multivariable mixed effects regressions fitted piecewise linear models to repeated measures of TBS as a function of time before or after the FMP; covariates were age at FMP, race/ethnicity, and body mass index. Prior to 1.5 years before the FMP, in the referent individual (a white woman with age at FMP of 52.2 years and body mass index of 28.0 kg/m2), TBS evidenced no change (slope 0.12% per year, P = 0.2991). TBS loss began 1.5 years before the FMP, declining by 1.16% annually (P < 0.0001). Starting 2 years after the FMP, annual rate of TBS loss lessened to 0.89% (P < 0.0001). In the 5 years before through the 5 years after the FMP, in the referent individual, total TBS decline was 6.3% (P < 0.0001), but black participants' total TBS loss was 4.90% (P = 0.0008, difference in black and white 10-year change). Results for Japanese did not differ from those of white women.

Conclusions: The occurrence of an MT-related decline in TBS supports the thesis that this period is particularly damaging to skeletal integrity.

Keywords: cohort; epidemiology; longitudinal; menopause; trabecular bone score.

Figure 1.

Derivation of the analysis sample for TBS in relation to the FMP. Participants are from the SWAN-TBS. Abbreviations: FBS, final menstrual period; SWAN, Study of Women’s Health Across the Nation; TBS, trabecular bone score.

Figure 2.

LOESS plots of TBS_TH in relation to BMI at baseline, in the Study of Women’s Health Across the Nation Trabecular Bone Score Study (N = 1375). Blue curves illustrate mean values; cross-sectional, 95% confidence intervals are indicated by the red curves. We accounted for the nonlinear relation between BMI and TBS_TH by using BMI splines in our models (see the Data Analysis section). Abbreviations: BMI, body mass index; LOESS, locally estimated scatterplot smoothing; TBS_TH, thickness-corrected trabecular bone score.

Figure 3.

LOESS plots of baseline normalized values of TBS_TH in relation to time before or after the FMP in the analysis sample. Participants are from the Study of Women’s Health Across the Nation Trabecular Bone Score Study. Blue curves illustrate mean values. Cross-sectional, 95% confidence intervals are indicated by the red curves. Number of observations is 6831. To minimize outlier influence, the plot is truncated at the extremes of FMP-time, 8 years before FMP (5th percentile) and 10 years after FMP (95th percentile). The LOESS plot presents a cross-section at each time; thus, it is influenced by the sample composition at each cross-section and by between-women differences. Therefore, the LOESS plot is used only to develop a hypothesis about the functional form of the relation between the exposure (FMP time) and the outcome (TBS_TH). Abbreviations: LOESS, locally estimated scatterplot smoothing; FMP, final menstrual period; TBS_TH, thickness-corrected trabecular bone score.

Figure 4.

Cumulative change in thickness-adjusted trabecular bone score during the 10-year interval spanning 5 years before through 5 years after the final menstrual period as function of body mass index, Study of Women’s Health Across the Nation Trabecular Bone Score Study. The solid black line illustrates the mean value of 10-year change across each of 3 body mass index ranges (<24, 24-31, and >41); dashed lines describe the 95% confidence interval. Model is adjusted for race, age at final menstrual period, and study site (see the Data Analysis section). Abbreviations: LCL, lower confidence limit; UCL, upper confidence limit.