Heart rate reserve predicts cardiovascular death among physically unfit but otherwise healthy middle-aged men: a 35-year follow-up study

BackgroundHeart rate reserve (HRR) has been reported to be inversely associated with cardiovascular (CV) disease and death. The impact of physical fitness (PF) on this relationship has not, however, been described in detail. We investigated how different levels of PF influenced the association between HRR and CV death during a 35-year follow-up.Methods and resultsHRR and PF were measured in 2014 apparently healthy, middle-aged men during a symptom-limited bicycle exercise test in 1972–75. The men were divided into tertiles (T1-T3) by age-adjusted HRR. Morbidity and mortality data were registered from hospital charts through 2007 and the Norwegian Cause of Death Registry. Adjusted Cox proportional hazard regression models were used to calculate risks. Incidence of CV death was 528 (26%) during median 30 years of follow-up. Men with the lowest HRR had 41% (HR 1.41 [1.14–1.75]) increased risk of CV death compared with the men with the highest. We found a significant interaction between age-adjusted PF and HR...