Incense Use and Cardiovascular Mortality among Chinese in Singapore: The Singapore Chinese Health Study

BACKGROUND Incense burning is common in many parts of the world. Although it is perceived that particulate matter from incense smoke is deleterious to health, there is no epidemiologic evidence linking domestic exposure to cardiovascular mortality. OBJECTIVE We examined the association between exposure to incense burning and cardiovascular mortality in the Singapore Chinese Health Study. METHODS We enrolled a total of 63,257 Singapore Chinese 45-74 years of age during 1993-1998. All participants were interviewed in person to collect information about lifestyle behaviors, including the practice of burning incense at home. We identified cardiovascular deaths via record linkage with the nationwide death registry through 31 December 2011. RESULTS In this cohort, 76.9% were current incense users, and most of the current users (89.9%) had burned incense daily for ≥ 20 years. Relative to noncurrent users, current users had a 12% higher risk of cardiovascular mortality [multivariable adjusted hazard ratio (HR) = 1.12; 95% CI: 1.04, 1.20]. The HR was 1.19 (95% CI: 1.03, 1.37) for mortality due to stroke and 1.10 (95% CI: 1.00, 1.21) for mortality due to coronary heart disease. The association between current incense use and cardiovascular mortality appeared to be limited to participants without a history of cardiovascular disease at baseline (HR = 1.16; 95% CI: 1.07, 1.26) but not linked to those with a history (HR = 1.00; 95% CI: 0.86, 1.17). In addition, the association was stronger in never-smokers (HR = 1.12; 95% CI: 1.02, 1.23) and former smokers (HR = 1.19; 95% CI: 1.00, 1.42) than in current smokers (HR = 1.05; 95% CI: 0.91, 1.22). CONCLUSIONS Long-term exposure to incense burning in the home environment was associated with an increased risk of cardiovascular mortality in the study population.