Deconstructing sex differences in C-reactive protein trends over time.

Objectives: Heightened inflammatory state, as measured by circulating C-reactive protein (CRP) levels, can promote inflammation-mediated disease risk. It is important to account for population fluctuation and sex variation in serum CRP concentrations on overall time trends.

Methods: Using the National Health and Nutrition Examination Survey data, we specify linear and algebraic decomposition models separately by sex to identify the drivers of the changing trends in the distribution of CRP values in the population.

Results: We found a nonsignificant overall increase in CRP, but a significant decrease among women and increase among men, over a 10-year period. We then used linear and algebraic decomposition techniques to identify the sources of change in CRP over time, separately for women and men. CRP increased among men mainly because lifestyle/health characteristics worsened over time, and because the size of socioeconomic/demographic groups with higher CRP increased and the size of groups with lower CRP decreased. The downward shift in CRP among women occurred because the typical woman across all cohorts had lower CRP levels.

Conclusions: We identified two fundamentally different processes of change driving the decline and rise in CRP values among women and men, respectively.