Reported exposure to passive smoking in childhood and adulthood has been found to be associated with a 50–52% increased risk of developing lung cancer in both men and women, according to a long-term prospective cohort study published in the European Respiratory Journal.
Using data from the Nord-Trøndelag Health Survey 2 (HUNT 2), an ongoing health survey of the adult population of the county of Nord-Trøndelag, Norway, researchers investigated the influences of passive smoking during childhood and adulthood on the development of lung cancer, both overall and by histologic type.
Participants were grouped into four passive smoking categories based on question data: those never exposed to passive smoking, those exposed in childhood only, those exposed in adulthood only, and those exposed in both periods; responses from the HUNT2 population data were linked with data from the Cancer Registry of Norway.
Competing-risks regression models were applied to estimate the sub-distribution hazard ratios (SHRs) which adjusted for: age, sex, family history of cancer, education, economic difficulties, pack-years of active smoking, BMI, physical activity and alcohol consumption.
Among the 56,772 participants with a median follow-up time of 18.2 years, all three passive smoking groups had an increased risk of small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC); no significant effect modification by sex was observed for either lung cancer overall or histologic types.
The authors note that the study could be limited by inaccuracies in the self-reporting of passive smoking and state that association estimates should be interpreted with caution, and also highlight that passive smoking status reflected mainly at-home exposure, but not the total exposure.