Coronary risk factors and exercise test performance in asymptomatic hypercholesterolemic men: Application of proportional hazards analysis

David J. Gordon, Jeffrey L. Probstfield, Carl Rubenstein, W. Fraser Bremner, Arthur S. Leon, John M. Karon, Jane Third, Hope Bryan, Leonard Schwartz, William Insull, L. Thomas Shefield

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

The association of established coronary risk factors with submaximal graded treadmill exercise test performance was examined in 6,850 asymptomatic, white 347-59-year-old hypercholesterolemic men screened between 1973 and 1976 at 12 North American Lipid Research Clinics for participation in their Coronary Primary Prevention Trial. The prevalence of ischemic electrocardiographic responses (ij mm S-T segment depression) was 8.6%. The Cox proportional hazards method was adapted so as to take into account the level of exercise at which ischemic responses occurred and to which subjects without ischemic responses were exposed. The results were compared with those obtained by standard logistic regression. In both models, age, blood pressure, plasma cholesterol, and (inversely) plasma high-density lipoprotein cholesterol and alcohol consumption were significant independent predictors of an ischemic response to exercise. Surprisingly, ischemic responses were less frequent in smokers than in nonsmokers. However, when the proportional hazards method was used, cigarette smoking was weakly but significantly (p < 0.01) predictive of an ischemic response on the treadmill. Results from this model differed from those of the logistic model because the former takes into account the reduced exercise capacity of smokers, which renders them less likely to reach workloads sufficient to induce myocardial ischemia. The proportional hazards model similarly demonstrated a possible beneficial effect of habitual physical activity which was not apparent in the logistic model. Quetelet index and plasma triglyceride were only weakly associated with the probability of an ischemic response, and did not contribute significantly to either model.

Original languageEnglish (US)
Pages (from-to)210-224
Number of pages15
JournalAmerican journal of epidemiology
Volume120
Issue number2
DOIs
StatePublished - Aug 1984

Bibliographical note

Funding Information:
Received for publication June 29, 1983, and in final form December 27, 1983. Abbreviations: HR, heart rate; PMHR, predicted maximal heart rate. 1Lipid Metabolism-Atherogenesis Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20205 (address for reprint requests). 2The Methodist Hospital, Baylor College of Medicine, Houston, TX. 3Oklahoma Medical Research Foundation, Oklahoma City, OK. * Clinical Research Center and Lipid Research Clinic, University of Cincinnati College of Medicine, Cincinnati, OH. 6 Laboratory of Physiological Hygiene, University of Minnesota, Minneapolis, MN. 6 Department of Biostatistics, University of North Carolina, Chapel Hill, NC. 7St. Michael's Hospital, Toronto, ON, Canada. 8Central Electrocardiographic Laboratory, University of Alabama, Birmingham, AL. Supported by National Heart, Lung, and Blood Institute Contracts: N01-HV1-2156-L, N01-HV1-2158-L, N01-HV1-2157-L, N01-HV1-2160-L, N01-HV1-2161-L, N01-HV1-2243-L, N01-HV2-2914-L, N01-HV2-2915-L, N01-HV1-2159-L, Y01-HV3-0010-L, N01-HV2-2932-L, N01-HV3-2961-L, N01-HV2-2913-L, N01-HV2-2917-L and N01-HV6-2941-L. The authors gratefully acknowledge the important contributions of the Lipid Research Clinics Intervention and Directors Committees (listed below) and of others, too numerous to list here, who have worked in the program's centers and support facil- ities and without whom a study as ambitious as the Coronary Primary Prevention Trial could not have been undertaken. The authors also wish to thank Dr. Lars-Goran Ekelund for his constructive suggestions for this manuscript.

Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.

Keywords

  • Coronary disease
  • Exercise test
  • Hypercholesterolemia
  • Lipids
  • Mathematical models

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