Professional drivers and lung cancer: a systematic review and meta-analysis

The objective of this study was to conduct a systematic review to provide summarised evidence on the association between professional drivers and lung cancer in the last decade after taking into consideration the potential confounding effect of cigarette smoking. We systematically searched all published cohort and case-control studies in English from Medline and Embase, from January 1996 to January 2011. We extracted the risk estimate (i.e., RR, OR, and standardised mortality ratio) from each individual study, and meta-analysis was used to combine the RR of individual studies. The methodological quality of each study was assessed using a standard approach proposed by Downs and Black. Nineteen studies were included in the meta-analysis. A significantly increased risk of lung cancer (pooled smoking-adjusted RR 1.18, 95% CI 1.05 to 1.33) among professional drivers was observed after combining four cohort studies and nine case-control studies. A higher pooled RR was observed among smoking-adjusted studies reporting 10 years or more of employment (RR 1.19, 95% CI 1.06 to 1.34) as compared with the study having a shorter duration of employment (6 years) (RR 1.00, 95% CI 0.92 to 1.09). This systematic review revealed that a 18% excess risk of lung cancer was linked to professional drivers who are potentially exposed to diesel exhaust, after adjustment for the confounding effect of smoking. There is a tendency for a positive lung cancer gradient with increasing years of employment as a professional driver.