Cardiorespiratory fitness offsets aggravating effect of inflammation on sudden cardiac death

Cardiorespiratory fitness (CRF) and inflammation are both independently linked to sudden cardiac death (SCD) in middle-aged men, reports a recent study. However, better CRF seems to offset the impact of inflammation on SCD risk.

The study included 1,749 men aged 42–61 years who did not have a history of coronary heart disease. Inflammation was quantified as high-sensitivity C-reactive protein (hsCRP), levels of which were measured using an immunometric assay. Meanwhile, CRF was measured through a respiratory gas exchange analyser during exercise testing.

Over a median follow-up of 28.9 years, a total of 148 SCD events occurred. Multivariable-adjusted Cox proportional hazards analysis found that high vs normal hsCRP (>3 vs ≤3 mg/L) increased the risk of SCD by 65 percent (hazard ratio [HR], 1.65, 95 percent confidence interval [CI], 1.11–2.45). Further adjustments for CRF did not meaningfully change this interaction (HR, 1.62, 95 percent CI, 1.09–2.40).

In contrast, high vs low CRF (according to the median value of 9.0 metabolic equivalents) suppressed SCD risk by nearly 40 percent (HR, 0.61, 95 percent CI, 0.42–0.89). Adjusting for hsCRP likewise did not substantially alter the findings (HR, 0.64, 95 percent CI, 0.44–0.93).

Of note, Kaplan-Meier analysis found that SCD risk was highest in men with high hsCRP and low CRF. Meanwhile, those with normal hsCRP but high CRF saw significantly lower SCD risk.

“There is … an interplay between hsCRP, CRF, and SCD risk,” the researchers said. “High fitness levels appear to offset the increased SCD risk related to high levels of hsCRP.”