Interplay Between Fitness, Systolic Blood Pressure and Sudden Cardiac Death (from a Cohort Study)

Modifiable risk factors, such as blood pressure and cardiorespiratory fitness (CRF) play a role in the genesis of sudden cardiac death (SCD). However, data on their joint contributions to SCD risk are scarce. We aimed to evaluate the interplay between systolic blood pressure (SBP), CRF, and SCD risk in a cohort of men. Resting SBP was measured using a random-zero sphygmomanometer and CRF was assessed using a respiratory gas exchange analyzer during clinical exercise testing at baseline in 2,291 men aged 42 to 61 years. SBP was classified as normal and high (<140 and ≥140 mm Hg, respectively) and CRF as low, medium, and high. Cox regression analysis was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for SCD. A total of 262 SCDs occurred during a median follow-up of 28.2 years. Comparing high versus normal SBP, the multivariable-adjusted HR (95% CI) for SCD was 1.35 (1.03 to 1.76). Comparing low versus high CRF levels, the corresponding adjusted HR (95% CI) for SCD was 1.81 (1.23 to 2.65). The HRs remained similar when SBP was further adjusted for CRF and CRF was further adjusted for SBP. Men with high SBP and low CRF compared with normal SBP and medium-high CRF, had an increased risk of SCD (HR 2.67, 95% CI 1.76 to 4.05), with no significant evidence of an association between men with high SBP and medium-high CRF and SCD risk (HR 1.38, 95% CI 0.84 to 2.26). There was modest evidence of an additive interaction between SBP and CRF in relation to SCD. In conclusion, there exists an interplay between SBP, CRF, and SCD risk in middle-aged and older men. Medium to high CRF levels may mitigate the increased risk of SCD in subjects with high SBP.