Effects of husbands' smoking on the incidence of lung cancer in Korean women

BACKGROUND: Although smoking remains uncommon among Korean women, lung cancer mortality is rapidly escalating. METHODS: We investigated the effects of spousal smoking in 160130 Korean women, aged 40-88, who received health insurance from the Korea Medical Insurance Corporation (KMIC). Exposure data were collected during medical examinations conducted between April 1992 and June 1994. The primary outcome variable was the incidence of lung cancer defined by hospital admissions between July 1994 and December 1997. Standardized rates for the incidence of lung cancer were assessed according to the smoking habits of their husbands. RESULTS: At baseline (n = 160 130), 53.9% of husbands were smokers and 23.3% were ex-smokers, while 1.1% of wives (n = 1756) were current smokers and 0.6% (n = 938) were ex-smokers. During follow-up, 79 cases of lung cancer occurred among non-smoking wives (n = 157436). Wives of heavy smokers were found to have a higher risk of developing lung cancer. The husbands' smoking habits did not affect their wives' risk of developing other cancers such as those of the stomach, liver and cervix, but they did affect breast cancer, which has a significantly higher risk in relation to the longer duration of husbands' smoking. In Poission regression models, adjusting for the age of both husband and wife, socioeconomic status, occupation, residency and vegetable intake, the rate ratio (RR) of lung cancer in non-smoking wives was 1.9 (95% CI: 1.0-3.5) in current smokers and 1.3 (95% CI: 0.6-2.7) in ex-smokers. The RR of lung cancer was 3.1 (95% CI: 1.4-6.6) in wives of husbands who had smoked for 30 years or more compared with wives of non-smoking husbands. CONCLUSION: In Korea, the incidence of lung cancer is higher among non-smoking women whose husbands smoke, and a dose-response relationship seems to exist.