Introduction: The time for inflammatory markers of former smokers to revert to never smoker levels is still controversial, ranging from 5 to 20 years. We aimed to determine the time from smoking cessation for white blood cell (WBC) count and serum C-reactive protein (CRP) levels to return to those of never-smokers, after adjusting for confounding factors and for secondhand smoke (SHS) exposure among participants of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil).
Methods: Cross-sectional analysis of baseline participants of ELSA-Brasil. We used linear regression analysis and generalized linear models with gamma distribution and logarithmic link function to estimate the association of WBC count and CRP levels with time from smoking cessation. The following confounding factors were considered: sex, age, education, SHS, alcohol consumption, leisure-time physical activity, BMI, total cholesterol/HDL ratio, hypertension, diabetes, cardiovascular disease, and chronic obstructive pulmonary disease (COPD). Results: After all adjustments, time from smoking cessation <10 years remained associated with higher WBC count (eg, time from smoking cessation ≥ 5 and <10 years: β: 167.92; 95%CI: 23.52 312.31), while only time from smoking cessation <1 year remained associated with higher arithmetic mean of CRP (AMR: 1.26, 95%CI: 1.03‒1.54).
Conclusions: Levels of inflammatory markers were similar to those of never-smokers 1 year after smoking cessation for CRP and 10 years after for WBC.
Implications: The results may add to the arsenal health professionals have to encourage their patients to quit smoking, as some harms from smoking appear to revert to never-smokers' level sooner than previously reported. Longitudinal studies should confirm our findings.
© The Author 2017. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: firstname.lastname@example.org.