Cigarette smoking, tar yields, and non-fatal myocardial infarction: 14000 cases and 32000 controls in the United KingdomBMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.7003.471 (Published 19 August 1995) Cite this as: BMJ 1995;311:471
- S Parish, senior research fellowa,
- R Collins, British Heart Foundation senior research fellowa,
- R Peto, professor of medical statistics and epidemiologya,
- L Youngman, senior research fellowa,
- J Barton, senior administratora,
- K Jayne, senior administrator,
- R Clarke, research fellowa,
- P Appleby, research fellowa,
- V Lyon, research fellowa,
- S Cederholm-Williams, directorb,
- J Marshall, research fellowb,
- P Sleight, professor emeritus of cardiovascular medicinea,
- For the International Studies of Infarct Survival (ISIS) Collaborators
- aISIS, BHF/ICRF/MRC Clinical Trial Service Unit and Epidemiological Studies Unit, Nuffield Department of Clinical Medicine, Radcliffe Infirmary, Oxford OX2 6HE and Cardiac Department, John Radcliffe Hospital, Oxford OX3 9DU
- bOxford Bio-Research Laboratory, Magdalen Science Park, Oxford OX4 4GA
- Correspondence to: Dr Parish.
- Accepted 19 August 1995
Objectives: To assess the effects of cigarette smoking on the incidence of non-fatal myocardial infarction, and to compare tar in different types of manufactured cigarettes.
Methods: In the early 1990s responses to a postal questionnaire were obtained from 13926 survivors of myocardial infarction (cases) recently discharged from hospitals in the United Kingdom and 32389 of their relatives (controls). Blood had been obtained from cases soon after admission for the index myocardial infarction and was also sought from the controls. 4923 cases and 6880 controls were current smokers of manufactured cigarettes with known tar yields. Almost all tar yields were 7-9 or 12-15 mg/cigarette (mean 7.5 mg for low tar (<10 mg) and 13.3 for medium tar (>/=10 mg)). The cited risk ratios were standardised for age and sex and compared myocardial infarction rates in current cigarette smokers with those in non-smokers who had not smoked cigarettes regularly in the past 10 years.
Results: At ages 30-49 the rates of myocardial infarction in smokers were about five times those in non-smokers (as defined); at ages 50-59 they were three times those in non-smokers, and even at ages 60-79 they were twice as great as in non-smokers (risk ratio 6.3, 4.7, 3.1, 2.5, and 1.9 at 30-39, 40-49, 50-59, 60-69, 70-79 respectively; each 2P<0.00001). After standardisation for age, sex, and amount smoked, the rate of non-fatal myocardial infarction was 10.4% (SD 5.4) higher in medium tar than in low tar cigarette smokers (2P=0.06). This percentage was not significantly greater at ages 30-59 (16.6% (7.1)) than at 60-79 (1.0% (8.5)). In both age ranges the difference in risk between cigarette smokers and non-smokers was much larger than the difference between one type of cigarette and another (risk ratio 3.39 and 3.95 at ages 30-59 for smokers of similar numbers of low and of medium tar cigarettes, and risk ratio 2.35 and 2.37 at ages 60-79). Most possible confounding factors that could be tested for were similar in low and medium tar users, with no significant differences in blood lipid or albumin concentrations.
Conclusion: The present study indicates that the imminent change of tar yields in the European Union to comply with an upper limit of 12 mg/cigarette will not increase (and may somewhat decrease) the incidence of myocardial infarction, unless they indirectly help perpetuate tobacco use. Even low tar cigarettes still greatly increase rates of myocardial infarction, however, especially among people in their 30s, 40s, and 50s, and far more risk is avoided by not smoking than by changing from one type of cigarette to another.
Funding The ISIS trials and epidemiological studies were supported by the manufacturers of the study drugs19 20 and by the British Heart Foundation, Imperial Cancer Research Fund, Medical Research Council, and Tobacco Products Research Trust of the Independent Scientific Committee on Smoking and Health, Department of Health.
Conflict of interest None.
- Accepted 19 August 1995