S. Parish et al., CIGARETTE-SMOKING, TAR YIELDS, AND NONFATAL MYOCARDIAL-INFARCTION - 14000 CASES AND 32000 CONTROLS IN THE UNITED-KINGDOM, BMJ. British medical journal, 311(7003), 1995, pp. 471-477
Objectives-To assess the effects of cigarette smoking on the incidence
of non-fatal myocardial infarction, and to compare tar in different t
ypes of manufactured cigarettes. Methods-In the early 1990s responses
to a postal questionnaire were obtained from 13 926 survivors of myoca
rdial infarction (cases) recently discharged from hospitals in the Uni
ted Kingdom and 32 389 of their relatives (controls). Blood had been o
btained from cases soon after admission for the index myocardial infar
ction and was also sought from the controls. 4923 cases and 6880 contr
ols were current smokers of manufactured cigarettes with known tar yie
lds. 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 (greater than or equal t
o 10 mg)). The cited risk ratios were standardised for age and sex and
compared myocardial infarction rates in current cigarette smokers wit
h those in non-smokers who had not smoked cigarettes regularly in the
past 10 years. Results-At ages 30-49 the rates of myocardial infarctio
n 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 respectiv
ely; 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). Thi
s 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 di
fference between one type of cigarette and another (risk ratio 3.39 an
d 3.95 at ages 30-59 for smokers of similar numbers of low and of medi
um tar cigarettes, and risk ratio 2.35 and 2.37 at ages 60-79). Most p
ossible confounding factors that could be tested for were similar in l
ow and medium tar users, with no significant differences in blood lipi
d or albumin concentrations. Conclusion-The present study indicates th
at the imminent change of tar yields in the European Union to comply w
ith an upper limit of 12 mg/cigarette will not increase (and may somew
hat decrease) the incidence of myocardial infarction, unless they indi
rectly help perpetuate tobacco use. Even low tar cigarettes still grea
tly increase rates of myocardial infarction, however, especially among
people in their 30s, 40s, and 50s, and far more risk is avoided by no
t smoking than by changing from one type of cigarette to another.