Environmental Tobacco and Wood Smoke Increase the Risk of Legg-Calve-Perthes Disease

The etiology of Legg-Calv,-Perthes disease (LCPD) remains unknown. A few studies have suggested passive smoke inhalation may be a risk factor, although the association is not confirmed and a causal relationship has not been established. We therefore undertook this study to confirm an association between environmental tobacco smoke, firewood smoke, and socioeconomic status and the risk of LCPD. We prospectively recruited 128 children with LCPD and 384 children attending the hospital for other orthopaedic complaints. The control subjects were frequency-matched with the cases by age and gender. Conditional logistic regression was used to assess the association between the exposures and risk of LCPD. The main risk factors for LCPD were indoor use of a wood stove (adjusted odds ratio [OR], 2.56) and having a family member who smoked indoors (adjusted OR, 2.07). Children from the middle socioeconomic group appeared to be at a greater risk of developing LCPD (adjusted OR, 3.60). This study provides further evidence that environmental tobacco smoke is associated with an increased risk of LCPD. Exposure to wood smoke also appears to be a risk factor. However, it remains unclear why there are profound differences in the incidence of the disease between regions when the prevalence of smoking is comparable and why bilateral involvement and familial disease are infrequent. Level III, case-control study. See the Guidelines for Authors for a complete description of levels of evidence.