Background: Passive smoking appears to increase the risk of meningococcal disease (MD) in adolescents. Whether this effect is attributable to exposure to cigarette smoke or contact with smokers is unknown.
Methods We conducted a prospective population-based case–control study wi:th age, sex matched-controls in 1:1 matching. Participants were 15–19 year old with MD recruited at hospital admission in six regions (65% of the population of England) from January 1999 through June 2000, and their matched controls. Data on potential risk factors were gathered by confidential interview, including seven passive smoking variables. Factor analysis was performed to assess the dimensionality of the passive smoking exposure variables. The data were analysed with univariate and multivariate conditional logistic regression.
Results: 144 case–control pairs were recruited (51% male; median age 17.6). Factor analysis identified two independent factors representing passive smoking (P < 0.01), one associated with ‘exposure to smoke’, the other with ‘smoker contact’. Only smoker contact was a significant risk factor for MD (OR = 1.8; 95% CI 1.0–3.3; P = 0.05). In multivariate analysis this factor was still associated with MD independently of potential confounders such as active smoker status and household crowding.
Conclusion: Contact with smokers is associated with increased risk of MD in adolescents. This is more likely to be due to higher carriage rates in smokers than to exposure to smoke and emphasizes the importance of public health measures to stop smoking. In epidemiological studies that assess risk from passive smoking, exposure to smoke should be differentiated where possible from contact with smokers.
Note the authors disclosed COI:
Conflict of interest: R.B. has acted as a paid consultant for Wyeth, GSK, and Aventis Pasteur. DA has spoken on the methodology of adverse drugs reactions in HIV at a scientific meeting attended by several pharmaceutical companies and sponsored by GSK. An honorarium was paid to her department. The other authors have no conflicts of interest to declare.
I find this interesting on a couple of levels. First is of course the obvious one -- creating the image of dirty, diseased smokers. But also -- it calls into question whether other passive smoking studies are confounded by "contact with smokers" -- which for those of us with more than two brain cells -- also means confounding with SES, occupation, geograohic location and all sorts of other things.