Efficacy of genotype notification to Japanese smokers on smoking cessation—An intervention study at workplace☆
Introduction
Smoking is well known as a leading cause of many diseases. Globally, an 85% of male lung cancer and 47% of female lung cancer was estimated to be attributable to tobacco smoking [1]. Cigarette smoking is also a primary cause of deaths from other human cancers [2], [3], [4], [5], coronary heart disease, chronic pulmonary disease and stroke [6]. In addition to educating smokers about the harmfulness of tobacco smoking, informing smokers of their genotypes associated with the vulnerability to the harms of smoking might be effective measures to induce them to quit smoking. The effects were hypothesized due to the recognition of disease risk as well as health consciousness elevated with genotype testing. According to Health Belief Model, behavior change (e.g. smoking cessation) is dependent on the people's recognition of themselves to be at risk of severe health consequences resulting from their behavior (e.g. they believe that smoking damages their health) [7]. As explained in Expanded Parallel-Process Model, the more people believe they are susceptible to a serious threat (e.g. high perceived risk or harboring high risk genotype), the more they are motivated to initial the evaluation of the recommended response (e.g. smoking cessation) [8], [9].
To date, there are a few randomized intervention studies to examine the efficacy of genotype notification. A study in the United States evaluated the long-term impact of genetic susceptibility biomarker (CYP2D6 genotype) feedback on smoking behavior change, resulting that the genetic susceptibility feedback did not improve the cessation rate [10], [11]. Another study reported that smokers notified to have GSTM1 genotype had a high cessation rate compared with the control group [12]. Since telephone counseling was provided only for the notified group, the contribution of genotype notification to the higher cessation rate was undetermined. A study in the United Kingdom to examine the psychological impact of GSTM1 genotype testing for smokers were found that those with GSTM1 null type had greater motivation to quit smoking, and that the depression among the genotype notified group was significantly low one week after the notification and not different two months after [13].
In Japan, there were also several reports evaluating the efficacy of genotype notification on smoking cessation [14], [15], [16], [17]. In those studies, genotypes of the genes possibly modifying smoking-related disease risks, L-myc, GSTM1, GSTT1, NQO1, and CYP1A1, were applied. In our previous studies, smoking elevated markedly the risk of lung cancer among those with L-myc SS (odds ratio, OR = 3.19; 95% CI 0.92–11.06) and LS (OR = 2.30; 95% CI 1.05–5.04) genotypes relative to among those with LL genotype (OR = 0.92; 95% CI 0.32–2.68) [18], and for the risk of esophageal cancer, OR = 7.57 (95% CI 1.91–30.03), 6.40 (2.74–14.95), and 1.77 (0.54–5.75), respectively [19]. This L-myc polymorphism is also reported to affect the prognosis of lung cancer [20], [21]. The L-myc polymorphism examined here is a T to A variation located in the second intron of the L-myc gene that produces short (S) and long (L) fragments after digestion by EcoRI, the precise biological influence of which is not yet fully clarified [20], [21]. Among those studies, one at a cancer hospital showed a significantly higher cessation rate in 100 female smokers notified of L-myc genotype (p = 0.024), but not in 145 male smokers, compared with the controls (119 female smokers and 130 male smokers). The insignificant result among the males could be due to the limited effect or due to the small statistical power. This study aimed to re-examine the effects of L-myc genotype notification to smokers on their smoking behavior in a male-dominant workplace with larger number of male subjects, and also to re-evaluate the efficacy of genotype notification on smoking behaviors, which is currently still under controversy worldwide. The participants were enrolled at an annual health checkup, although the situation differed from the previous study whose participants were first-visit outpatients.
Section snippets
Design and participants
Subjects were employees of a bank, who answered to be a smoker for a questionnaire used at annual health checkup at workplace from July to December in 2002. Informed consent of genotype notification was obtained individually from each smoker after handing the participants a booklet named “Smoking and genetic polymorphism: what is the genetic traits to cause tobacco-related diseases. Hi smokers! Can your genes bear tobacco?”. The booklet was made of eight colored pages including information on
Results
Table 1 shows sex and age distributions of the 562 participants (527 males and 35 females). In the intervention group, 89.9% (243 males and 14 females) agreed the genotype testing. There were no differences in sex and age distributions between those who agreed and those who refused.
Table 2 shows the stage of smokers at one year after the enrollment. Those who stated to have quitted smoking were 22 (8.0%) among the 276 controls and 15 (5.8%) among the 257 genotype notified participants. The
Discussion
This study based on the questionnaire found that the cessation rate was 5.8% among the genotype notified participants, and 8.0% in the controls. The rate was not significantly different according to the L-myc genotype. There were no such severe substantial psychological/social problems as to require counseling relating with the genotype notification, although the percentage who stated to “relieved” was significantly low among those with LS or SS relative to those with LL, and that of “anxious”
Conflict of interests
The authors have no conflict of interests to declare.
Acknowledgments
This study was supported in part by a Grant-in-Aid for Cancer Research from the Japanese Ministry of Health, Labour and Welfare.
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This work was performed at the Bank of Tokyo-Mitsubishi UFJ (former Tokai Bank) and Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya, Japan. AH was a former resident, and NH were former staffs of Division of Epidemiology and Prevention, Aichi Cancer Center Research Institute, Nagoya, Japan.