Editor—It is well known that smoking is inversely correlated with education level; the highest percentage of smokers is found among those people who have not completed high school. This inverse correlation of smoking and education has been true for many years. It is referred to in the 15th edition (1977-9) of the Encyclopedia Britannica. Clearly, this casts suspicion on the data entry and the programming used by Enstrom and Kabat to perform their analysis,1 because they find that the highest frequency of smoking is associated with the highest level of education.
From their table 2 (male never smokers) and table 3 (female never smokers) sorted by smoking status of spouse, they show that the heaviest smokers (≥ 40 cigarettes/day) are more likely to have completed high school than are non-smokers. Further, among smokers, they show that for those smoking a higher number of cigarettes the likelihood of completing high school is greater.
Because the “never smoked/formerly smoked” group does not show the expected higher proportion of high school graduates, this implies that there were a sizeable number of smokers included among the non-smokers; that would account for the spouses of “non-smokers” not exhibiting a lower rate of heart disease.
Competing interests: None declared.
References
- 1.Enstrom JE, Kabat, GC. Environmental tobacco smoke and tobacco related mortality in a prospective study of Californians, 1960-98. BMJ 2003;326: 1057. (17 May.) [DOI] [PMC free article] [PubMed] [Google Scholar]