Association of serum cotinine levels and hypertension in never smokers.

Hypertension is a major public health problem. Identifying novel risk factors for hypertension, including widely prevalent environmental exposures, is therefore important. Active smoking is a well-known risk factor for hypertension and cardiovascular diseases. However, there are no studies investigating the relationship between secondhand smoke exposure, measured objectively by serum cotinine, and high blood pressure among never smokers. We examined 2889 never smokers from the National Health and Nutrition Examination Survey 2005-2008. Our exposure of interest was secondhand smoke exposure among never smokers, estimated by serum cotinine level, and our main outcome was hypertension (n=1004). We found that in never smokers, higher serum cotinine levels were positively associated with hypertension. In comparison with those with serum cotinine levels ≤ 0.025 ng/mL, the multivariable odds ratio (95% confidence interval) of hypertension among those with serum cotinine levels ≥ 0.218 ng/mL was 1.44 (1.01-2.04). In addition, higher serum cotinine was positively associated with mean change in systolic blood pressure (odds ratio [95% confidence interval], 3.24 [0.86-5.63]; P=0.0061). However, no association was present with diastolic blood pressure. In conclusion, in never smokers, higher secondhand smoke exposure measured objectively by serum cotinine levels was found to be associated with systolic blood pressure and hypertension independent of age, sex, ethnicity, education, alcohol drinking, body mass index, glycohemoglobin, total cholesterol, and other confounders.