WEDNESDAY, April 28, 2021 (HealthDay News) — There seems to be a causal association between secondhand smoke (SHS) exposure and oral cancer, according to a systematic review and meta-analysis published online April 26 in Tobacco Control.

Lorena C. Mariano, from the Instituto Universitário de Ciências da Saúde in Gandra, Portugal, and colleagues conducted a systematic review and meta-analysis to examine studies reporting the associations of SHS and the risk for oral cancer. Data were included for five studies, with a total of 1,179 cases and 5,798 controls and 3,452 individuals exposed and 3,525 not exposed to SHS.

The researchers found that the overall odds ratio for oral cancer was 1.51 (95 percent confidence interval, 1.20 to 1.91; P = 0.0004), without significant heterogeneity (I2= 0 percent; P = 0.41). Compared with nonexposed individuals, the risk for oral cancer was increased with duration of exposure of more than 10 to 15 years (odds ratio, 2.07; 95 percent confidence interval, 1.54 to 2.79; P < 0.00001), with no significant heterogeneity (I2= 0 percent; P = 0.76).

“Our systematic review and meta-analysis support a consistent and statistically significant association between SHS exposure and the risk of oral cancer,” the authors write. “Moreover, the analyses of exposure response, including by duration of exposure (more than 10 or 15 years) to SHS, further supports causal inference.”

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