Active and passive smoking and the incidence of asthma in the Black Women's Health Study.
BACKGROUND
Evidence linking active or passive smoking to the incidence of adult-onset asthma is inconsistent with both positive and inverse associations being reported. Most previous studies of active smoking have not accounted for passive smoke exposure, which may have introduced bias.


OBJECTIVE
To assess the separate associations of active and passive smoking to the incidence of adult-onset asthma in the U.S. Black Women's Health Study, a prospective cohort of African American women followed since 1995 with mailed biennial questionnaires.


METHODS
Active smoking status was reported at baseline and updated on all follow-up questionnaires. Passive smoke exposure during childhood, adolescence, and adulthood was ascertained in 1997. Asthma cases comprised women who reported doctor-diagnosed asthma with concurrent asthma medication use. Cox regression models were used to derive multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) for former and current smoking and for passive smoking among nonsmokers compared with a reference category of never active or passive smokers.


RESULTS
Among 46,182 participants followed from 1995 to 2011, 1,523 reported incident asthma. The multivariable HRs for former active smoking, current active smoking, and passive smoking only were, respectively, 1.36 (95% CI, 1.11-1.67), 1.43 (95% CI, 1.15-1.77), and 1.21 (95% CI, 1.00-1.45), compared with never active/passive smoking.


CONCLUSIONS
In this large population with 16 years of follow-up, active smoking increased the incidence of adult-onset asthma, and passive smoke exposure increased the risk among nonsmokers. Continued efforts to reduce exposure to tobacco smoke may have a beneficial effect on the incidence of adult-onset asthma.
1 Slone Epidemiology Center and.
Patricia F
PF
Coogan
Nelsy
N
Castro-Webb
Jeffrey
J
Yu
George T
GT
O'Connor
Julie R
JR
Palmer
Lynn
L
Rosenberg
D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D017668:Age of Onset; D000368:Aged; D001249:Asthma / Q000208:ethnology* / Q000209:etiology; D005260:Female; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012907:Smoking / Q000009:adverse effects* / Q000208:ethnology; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution / Q000009:adverse effects* / Q000706:statistics & numerical data; D016387:Women's Health / Q000706:statistics & numerical data*; D055815:Young Adult
D014028:Tobacco Smoke Pollution
asthma; cigarette smoking; cohort study; passive smoking