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Cigarette smoking remains, as it has been for decades, the number one public health enemy. In 1964, then-Surgeon General Luther Terry issued his now-famous report on the health risks conferred by cigarette smoking. Since then, many smokers have quit the habit, but others have unfortunately picked it up, in spite of many warnings by the public health establishment.
One concern has been that the message(s) about the health risks are not effectively reaching the appropriate target audiences. In particular, differences between white and African-American populations with respect to smoking behavior need to be better elucidated.
For example, it is known that incidence rates for lung cancer differ between black and white Americans, being higher for black males but lower for black females compared to their white counterparts. Thus such inter-racial differences was a major focus of an investigation by Dr. Theodore R. Holford of the Yale School of Public Health and colleagues, recently published in the journal Nicotine & Tobacco Research.
The investigators used data from the U.S. National Interview Surveys conducted from 1965 through 2012. They examined reported smoking behavior by whites and blacks born between 1890 and 1990, dividing these people into 10-year cohorts. Data they collected included age of smoking, number of cigarettes smoked, length of smoking, and age at which people quit. They used these data to construct yearly estimates of smoking initiation, cessation and intensity by age for each 10-year cohort of both white and black, male and female Americans.
For both white and black men, smoking initiation peaks in the late teens, and after the late 1950s and early 60s begins to decline. For women, since smoking was not considered acceptable, those born before 1910 had low rates of initiation — though they were slightly higher for black women. After about 1940, initiation rates were greater for white women than for blacks. The probability of initiation declines most precipitously after 1980 — but much more rapidly in black women than in whites.
As one might expect, the probability that a smoker would quit increased as he or she aged. Still, for both genders, blacks were less likely to quit than were whites. And all were more likely to quit after the early 1960s — i.e. after the Surgeon-General's report on smoking.
Because of the differences in smoking initiation and cessation, there were also racial and gender differences in smoking prevalence. Initially, the prevalence is greater in white men compared to blacks — about 75 percent of white men in their 20s smoked in the 1940 survey, compared to less than 70 percent of black men. But then by 1960 black men outstripped white with respect to smoking rates. For women born between 1930 and 1950, smoking prevalence was higher for whites at younger ages, but lower for older ages. At any age, smoking prevalence for women of both races was much lower at the peak (reached around 1960) than for men, never rising above 50 percent, and dropping in both after the mid-1960s.
Smoking intensity, defined as the number of cigarettes smoked per day, was much higher in whites than black across all age groups and years. That number peaked at about 27 for white men, and 20 for white women. Their black counterparts peaked at about 18 and 13 for men and women respectively. The duration of smoking is higher for white men initially, but at older ages is greater for blacks. For women, it is typically greater for whites than blacks.
When the data were expressed as pack-years — a person who smoked one pack per day for 30 years would have a 30 pack-year exposure — the differences seen for men at older ages were no longer apparent. Both white men and women had higher exposures when the pack-year metric was employed than their black counterparts.
At age 65, when many of the deleterious effects of smoking might be manifested, the differences between these metrics were substantial. When the pack-year metric was used, both white men and women had considerably greater smoking intensity than did black men and women. But when the mean cumulative years of smoking was used, the data were decidedly different, with black men having a greater exposure than white men at virtually every time point between 1975 and 2010. For women, initially whites had greater exposure than blacks, but by 1995 these were nearly the same.
The authors point out that pack-years and mean smoking duration are the most frequently used measures of smoking history. Because, they say, "smoking intensity improves estimates of risk, pack-years is not the optimal way to include this information." They also point out that the U.S. Preventive Services Task Force uses 30 pack-years as a criterion for lung cancer screening.
In addition, they note that black men, although they have a higher risk of lung cancer than white men, have a lower smoking history if pack-years are used as the metric. Thus cumulative smoking exposure may be a more accurate assessment of risk. Further, they state that although smoking exposure may be more accurate in predicting, risk, it's still not clear why the risk is greater in black men. They suggest that racial differences in rates of absorption and/or metabolism of the toxic components of cigarette smoke may be responsible.
