Abstract
IMPORTANCE: There has been an increasing trend of using noncigarette products, including waterpipe tobacco (WTP), worldwide. While cigarette smoking is a well-established risk factor for numerous cancers, little is known about the association between WTP smoking and cancer mortality. OBJECTIVE: To assess the association between WTP smoking and risk of cancer mortality in Vietnam. DESIGN, SETTING, AND PARTICIPANTS: This cohort study was based on data from the Hanoi Prospective Cohort Study, an ongoing study with a median (range) follow-up of 11.0 (0.1-11.6) years for participants aged 15 years or older in Northern Vietnam from 2007 through 2019. Data were analyzed from June 1 to September 1, 2023. EXPOSURES: Tobacco smoking and WTP smoking statuses. MAIN OUTCOMES AND MEASURES: Overall and site-specific cancer mortality. Cox proportional regression models were used to calculate the hazard ratio (HR) and 95% CIs for the associations between WTP smoking alone, cigarette smoking alone, and dual WTP and cigarette smoking and the risk of cancer death. RESULTS: A total of 554 cancer deaths were identified among the 39 401 study participants (mean [SD] age, 40.4 [18.8] years; 20 616 females [52.3%]). In multivariable models, compared with never smokers, ever smokers had a significantly increased risk of cancer mortality (HR, 1.87; 95% CI, 1.48-2.35). Exclusive WTP smokers had the highest risk of cancer mortality compared with never smokers (HR, 2.66; 95% CI, 2.07-3.43). Risk of cancer mortality was higher for dual smokers of WTP and cigarettes (HR, 2.06; 95% CI, 1.53-2.76) than for exclusive cigarette smokers (HR, 1.86; 95% CI, 1.41-2.45). As most smokers (95.6% [8897 of 9312]) were male, these patterns were more apparent in male participants. Compared with never smokers, exclusive WTP smoking among males was associated with an elevated risk of death from liver cancer (HR, 3.92; 95% CI, 2.25-6.85), lung cancer (HR, 3.49; 95% CI, 2.08-5.88), nasopharyngeal carcinoma (HR, 2.79; 95% CI, 1.27-6.12), and stomach cancer (HR, 4.11; 95% CI, 2.04-8.27). For exclusive WTP smokers, the risk of cancer mortality was highest among those who smoked 11 to 15 sessions per day (HR, 3.42; 95% CI, 2.03-5.75), started smoking at age 26 to 30 years (HR, 4.01; 95% CI, 2.63-6.11), smoked for 9 to 20 years (HR, 4.04; 95% CI, 2.16-7.56), and smoked 61 to 160 sessions annually (HR, 3.68; 95% CI, 2.38-5.71). For males, the risk of cancer death was lower for those who had quit smoking for more than 10 years, compared with those who quit smoking within 1 year (HR, 0.27; 95% CI, 0.11-0.66; P for trend < .001). CONCLUSION AND RELEVANCE: In this cohort study in Vietnam, WTP smoking alone or in combination with cigarette smoking was associated with an increased risk of cancer death due to liver cancer, lung cancer, nasopharyngeal carcinoma, and stomach cancer. A tailored program to control WTP smoking is warranted in Vietnam and low- and middle-income countries with a high prevalence of smoking and modest resources to address smoking-related issues.