An exposure-response relationship between multimorbidity and motor-vehicle accidents

Objective: Several health conditions are independently associated with an increased risk of experiencing a motor-vehicle accident (MVA). The objective of this study was to investigate the possibility of an exposure-response relationship between multimorbidity and MVAs using electronic health records. Methods: Driver-related MVA cases recorded between 2002 and 2012 were identified in Cerner Health Facts, a national electronic health record database in the United States. Cases were matched to five controls from the same health care facility on age, sex, and index date (2 years). Multimorbidity was defined as the total number of morbidities per patient, based on the prevalence of 13 predefined health conditions that were retrospectively assessed during the previous 2 years. The risk of MVA for individuals with increasing multimorbidity, relative to no morbidity, was estimated using conditional logistic regression. Additional analyses were conducted to evaluate possible effect modification by sex and age. Results: A total of 74,167 unique MVA cases were matched to 370,835 controls: 59.1% of study participants were males and the mean age was 37.0 +/- 0.0 years. Multimorbidity, having 2 or more health conditions, was more frequent in cases (8.0%) than in controls (5.6%), x(2) (1, N=445,002)=585.9, p < .0001. A positive association was detected between increasing multirriorbidity and MVA risk. Relative to no morbidity, the odds of MVA increased steadily with an increasing number of prevalent morbidities-from 1.11 (95% Cl 1.06-1.16) with two concurrent health conditions to 3.53 (95% CI 2.69-4.64) with six or more health conditions. Increasing MVA risk with increasing multimorbidity was more pronounced in women than men. Conclusions: This study found an overall increased risk of MVA with increasing multi morbidity, which was reproduced across sex and age categories. The important public health implications of these findings warrant replication with additional adjustment for driving habits. (C) 2017 Elsevier Ltd. All rights reserved.