title: Heart rate reserve predicts cardiovascular death among physically unfit but otherwise healthy middle-aged men: a 35-year follow-up study.
abstract: BACKGROUND
  Heart 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.
  
  
  RESULTS
  HRR 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 HRR. After stratifying the men by PF, results were statistically significant only among men with the lowest PF, where the men with lowest HRR had a 70% (HR 1.70 [1.12-2.67]) increased risk of CV death compared with the men with the highest.
  
  
  CONCLUSIONS
  Low HRR was independently associated with increased risk of CV death in apparently healthy, middle-aged men. The predictive impact of HRR on CV death risk was, however, confined to unfit men.
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway engekr@gmail.com.
authors.forename: Kristian
authors.initials: K
authors.lastname: Engeseth
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway.
authors.forename: Christian
authors.initials: C
authors.lastname: Hodnesdal
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway Centre for Clinical Heart Research, Oslo University Hospital, Norway.
authors.forename: Irene
authors.initials: I
authors.lastname: Grundvold
authors.affiliation: Department of Informatics, University of Oslo, Norway.
authors.forename: Knut
authors.initials: K
authors.lastname: Liestøl
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway.
authors.forename: Knut
authors.initials: K
authors.lastname: Gjesdal
authors.affiliation: Faculty of Medicine, University of Oslo, Norway.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Erikssen
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway.
authors.forename: Sverre E
authors.initials: SE
authors.lastname: Kjeldsen
authors.affiliation: Faculty of Medicine, University of Oslo, Norway.
authors.forename: Jan E
authors.initials: JE
authors.lastname: Erikssen
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway.
authors.forename: Johan
authors.initials: J
authors.lastname: Bodegard
authors.affiliation: Department of Cardiology, Oslo University Hospital, Ullevaal, Norway Faculty of Medicine, University of Oslo, Norway.
authors.forename: Per Torger
authors.initials: PT
authors.lastname: Skretteberg
mesh_terms: D000328:Adult; D000367:Age Factors; D001642:Bicycling; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000209:etiology / Q000401:mortality* / Q000503:physiopathology; D016009:Chi-Square Distribution; D005080:Exercise Test / Q000379:methods; D005500:Follow-Up Studies; D006304:Health Status; D006339:Heart Rate; D006801:Humans; D015994:Incidence; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D010809:Physical Fitness; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D013997:Time Factors
keywords: CVD risk prediction; Heart rate reserve; cardiovascular death; coronary heart disease; physical fitness