Baseline Body Mass Index Category and Incident Treated Hypertension in Australian Men: A Linked Prospective Cohort Study Using PBS/MBS Data

Figures

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  Figure 1. Kaplan–Meier hypertension‐free survival by baseline body mass index category, primary adult cohort (men aged ≥ 18 years, n = 12,742). Time since baseline in years is plotted on the horizontal axis and the probability of remaining free of treated hypertension is plotted on the vertical axis. Numbers at risk are shown beneath the plot.

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  Figure 2. Forest plot of hazard ratios for body mass index category across progressively adjusted Cox proportional hazards models. The reference category is normal weight. Hazard ratios are plotted on a logarithmic scale; horizontal lines denote 95% confidence intervals. Abbreviations: CI, confidence interval; HR, hazard ratio.

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  Figure 3. Scaled Schoenfeld residual plots for body mass index category with locally weighted regression smoothers (men aged ≥ 18 years, fully adjusted model). Time since baseline in years is plotted on the horizontal axis and the scaled Schoenfeld residual β(t) is plotted on the vertical axis for each pairwise contrast (underweight, overweight, and obese, each vs. normal weight). The smoothed regression curve lies approximately on the β(t) = 0 reference line across the follow‐up window for all three contrasts, with 95% confidence bands spanning the reference line, supporting the proportional hazards assumption.

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  Figure 4. Discrimination of nested risk models for incident treated hypertension. Harrell's C‐index is shown with 500‐replicate bootstrap percentile 95% confidence intervals. Body mass index category alone yields C = 0.605; adding age yields C = 0.672, adding diabetes treatment status yields C = 0.700, and the fully adjusted model yields C = 0.754. All between‐model differences exceed the pre‐specified threshold of 0.01, with confidence intervals excluding zero. Abbreviation: CI, confidence interval.

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  Figure 5. Calibration of the body mass index plus age model and the fully adjusted model at 5 years, partitioned by decile of predicted risk. The mean predicted 5‐year risk of treated hypertension in each decile is plotted on the horizontal axis against the observed Kaplan–Meier 5‐year risk in the same decile on the vertical axis, with Greenwood‐based 95% confidence intervals on observed risk. The diagonal line denotes perfect calibration.

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  Figure 6. Decision curve analysis for 5‐year incident treated hypertension with 150‐replicate bootstrap percentile 95% confidence ribbons. The threshold probability for triggering enhanced hypertension surveillance is plotted on the horizontal axis and net benefit is plotted on the vertical axis. The body mass index plus age model, the clinical model, and the fully adjusted model are compared against the treat‐all and treat‐none reference strategies. The fully adjusted model shows positive net benefit with confidence ribbons excluding zero between approximately 3% and 25%.