Tooth Loss and Risk of Lung Cancer among Urban Chinese Adults: A Cohort Study with Meta-Analysis

SIMPLE SUMMARY: The risk of lung cancer associated with tooth loss has not been fully addressed, especially for the potential interaction with smoking. This cohort study with meta-analysis first investigated the association between tooth loss and lung cancer risk stratified by smoking status using the Shanghai Men’s and Women’s Health Studies and then summarized epidemiologic findings to date, incorporating the current study and other published studies. Our findings suggest that tooth loss is associated with an increased risk of developing lung cancer, but smoking could modify the association. A meta-analysis of eight epidemiological studies also supports a strong link of tooth loss to lung cancer risk, particularly among current smokers. Improving dental care and oral health may be an effective strategy for lung cancer prevention in addition to smoking cessation. ABSTRACT: Epidemiological evidence on tooth loss and lung cancer risk remains limited, especially for smoking-specific associations. To investigate the association between tooth loss and lung cancer risk by smoking status, we first analyzed data from the Shanghai Men’s Health Study (n = 49,868) and the Shanghai Women’s Health Study (n = 44,309). Cox regression models were applied to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for lung cancer risk in relation to tooth loss. We also conducted a meta-analysis to summarize epidemiologic findings to date, incorporating results from the current study and six previously published studies. For 7.3 median follow-up years, 973 incident lung cancer cases (613 men and 360 women) were ascertained. After adjustment for major covariates, tooth loss was associated with an increased risk of lung cancer among men (HR [95% CI] for >10 teeth vs. none = 1.59 [1.21–2.11]) but not among women (0.86 [0.50–1.46]). The positive association was stronger among male current smokers (1.75 [1.26–2.45], p-interaction by smoking status = 0.04). In a meta-analysis incorporating 4052 lung cancer cases and 248,126 non-cases, tooth loss was associated with a 1.64-fold increased risk of developing lung cancer (relative risk [RR, 95% CI] for the uppermost with the lowest category = 1.64 [1.44–1.86]). The positive association was more evident among current smokers (1.86 [1.41–2.46]), but no significant associations were found among never or former smokers. Our findings suggest that tooth loss may be associated with an increased risk of lung cancer, and the association could be modified by smoking status.