Softening of monthly cigarette use in youth and the need to harden measures in surveillance

Introduction

A key indicator of starting cigarette use in young people is how many have smoked at least once during the previous 30 days (Starr et al., 2005). Monthly smoking by youth is widely employed to monitor “current” cigarette use. For example, a current national report on current cigarette use among middle and high school students in the United States uses monthly smoking (≥ 1 cigarette in the past 30 days) to measure current cigarette smoking and provides no further analysis of frequency or intensity of smoking, even though such measures were available (Centers for Disease Control and Prevention, 2013).

We explored changes over four decades in heavier levels of cigarette use associated with monthly use. Michael Russell in 1971 argued that “..., it requires no more than three or four casual cigarettes during adolescence virtually to ensure that a person will eventually become a regular dependent user”(Russell, 1971, p.3). But growing attention focuses on smokers who develop stable patterns of non-daily smoking (Hassmiller et al., 2003, Shiffman et al., 2012). One study followed non-daily smokers for 13 years (to age 21), finding that 26% continued to be non-daily smokers, 17% became daily smokers, and 57% no longer smoked (Kvaavik et al., 2014). Others have drawn attention to occasional smoking (e.g., Schane et al., 2009), but we wanted to explore systematic changes in relation to monthly smoking and ever smoking. If over the years monthly smoking was becoming more associated with heavier, daily smoking, this would be a “hardening” of smoking as an addiction; if monthly smoking was becoming more associated with lighter and non-daily smoking, this would be a “softening” of smoking as an addictive activity.

Methods

We analyzed public results from Monitoring The Future (MTF), which provides high quality, representative, yearly national estimates of cigarette use by 12th grade high school students (public and private) for 39 years in the Continental U.S. (Johnston et al., 2014). Use of this public, secondary source data is subject to Institutional Review Board exemption. In addition to measuring cigarette smoking in the past 30 days, it also measures “daily” smoking and smoking at least a half-a-pack of cigarettes per day (i.e., typically 10 + cigarettes per day), using answers to the question, “How frequently have you smoked cigarettes during the past 30 days?” with response options of “Not at all,” “Less than one cigarette per day,” “One to five cigarettes per day,” “About one-half pack per day,” “About one pack per day,” “About one and one-half packs per day,” and “Two or more packs per day.” This study is limited by the use of self-report measures and does not represent youth of school age who are not in school. We plot results and provide linear regression lines (with R²).

Results

For 12th grade students lifetime smoking and monthly smoking have dropped considerably from 1975 to 2013: by 48% or 35.5 percentage points for lifetime smoking and 56% or 20.4 percentage points for monthly smoking (see Fig. 1).

Fig. 2 shows the percentage of monthly smokers a) who are daily smokers and b) who are smokers of half-a-pack + per day, and c) the percentage of daily smokers who smoke a half-a-pack + per day. While lifetime and monthly smoking have dropped, daily smoking and heavier daily smoking have also dropped. The percentage of monthly smokers who smoked daily decreased by 29% (21.2 percentage points) and monthly smokers who smoked 10 + cigarettes/day dropped by 57% (28 percentage points). The percentage of daily smokers who smoked 10 + cigarettes/day decreased by 40% (26.5 percentage points); in 1975 a majority (two-thirds) of daily smokers reported half-a-pack + per day and in 2013 a minority (4 in 10) did so. Linear regression lines are reliable (Ps < .001, 2-tailed).

Discussion

These results indicate softening rather than hardening of “current smoking” and have important implications for tobacco surveillance and for tobacco research, in relation to a) increased likelihood of quitting smoking, b) health effects of cigarette smoking, and c) similar and interacting issues related to measuring the use of all tobacco/nicotine products.

Conflict of interest statement

No competing interest.