Analgesics and road traffic crashes in senior drivers: an epidemiological review and explorative meta-analysis on opioids.

Aim: To assess the epidemiological evidence associating the use of analgesics with the occurrence of road traffic crashes in senior drivers including a meta-analysis with specific focus on opioids.

Methods: Systematic literature review of articles published between 1991 and 2012 retrieved from major databases using relevant key words. Eligible articles were fully reviewed and the main characteristics and results summarized. The methodological quality was assessed using the Newcastle-Ottawa Scale. Heterogeneity tests and forest and funnel plots were used as part of the meta-analysis on opioids.

Results: From the potentially eligible articles, nine were selected (4 case-control, 1 case-crossover, and 4 cohort studies) of which four were of medium and five of high quality; seven investigated opioids and four non-steroidal anti-inflammatory drugs. Crash involvement (n=7) rather than responsibility (n=2) was investigated. Age and sex were the most common covariates adjusted for. Both opioids and non-steroidal anti-inflammatory drugs showed mixed results including differences across estimates between and within studies. A marginal positive effect was observed in the pooled analyses on opioids (n=6, OR 1.20; 95% CI 1.08-1.32).

Conclusions: The evidence is unconvincing in terms of number of studies, control of major confounders, and consistency of the results. The effect seen for opioids can be attributed to the lack of adjustment of key confounders such as concomitant illness or the consumption of alcohol or other psychoactive medications. There is a need for more efficient designs like larger population-based retrospective cohorts and nested case-control or case-crossover studies based on registers of high quality allowing adjustment for these factors and for the selection of unequivocal outcomes (e.g. drivers' responsibility) to produce more persuasive empirical evidence.