Nhanes-derived Normative Values For Exercise Blood Pressure: Where Do The Sex Differences Come From?

The systolic blood pressure (SBP) during moderate-intensity exercise (ExSBP) represents cardiovascular strain during tasks of daily living and is predictive of future cardiovascular disease. Unlike resting SBP, no normative data exist for ExSBP. PURPOSE: Create sex-specific normative data for the ExSBP during moderate-intensity exercise and determine what accounts for sex differences. METHODS: ExSBP during moderate-intensity treadmill walking was measured in 1557 male and 1445 female adults (20-49 years old, free from cardiovascular medication) during the 1999-2004 National Health and Nutrition Examination Survey (NHANES) representing 55,602,979 inhabitants of the USA (Figure A). Following a 2-minute warmup, subjects walked on a treadmill for 3 minutes at a speed and grade intended to elicit 60-80% of their age-estimated maximum heart rate. Blood pressure (automated ausculatory) and heart rate (ECG) were measured a rest and 2.5 minutes into the exercise. Exercise power was calculated based upon speed, grade and body mass. Complex samples analysis and log transformation were applied as recommended by NHANES. RESULTS: On average male adults exhibited ~22 mmHg greater ExSBP than female adults (Figures B and C). Normative values for healthy male and female adults in the USA are presented in Figure C. In addition to having a higher resting SBP (Figure A), ΔExSBP from resting was approximately 50% greater in male than female adults (Male 2.30 ± 0.002, Female 2.14 ± 0.002 Log ΔmmHg, P < 0.001). Simply covarying for differences in absolute power output during the exercise (P < 0.001) eliminated the sex differences in ΔExSBP (Male 1.50 ± 0.001, Female 1.49 ± 0.01 Log ΔmmHg, P = 0.668). CONCLUSIONS: Male adults in the USA exhibit greater SBP during moderate-intensity walking than female adults. Differences in resting pressure and exercise power output account for most of the difference. These normative data provide a point of reference for future studies and interventions.Bobbit Heart Disease Award