Drug overdose and the risk of cardiovascular diseases: a nested case-control study.

North America has been experiencing an unprecedented epidemic of drug overdose. This study investigated the associations of drug overdose with the risk of cardiovascular disease (CVD) and 11 major CVD subtypes. This nested case–control study was based on a cohort of 20% random sample of residents in British Columbia, Canada, who were aged 18–80 years and did not have known CVD at baseline (n = 617,863). During a 4-year follow-up period, persons who developed incident CVD were identified as case subjects, and the onset date of CVD was defined as the index date. For each case subject, we used incidence density sampling to randomly select up to five control subjects from the cohort members who were alive and did not have known CVD by the index date, were admitted to an emergency department or hospital on the index date for non-CVD causes, and were matched on age, sex, and region of residence. Overdose exposure on the index date and each of the previous 5 days was examined for each subject. This study included 16,113 CVD case subjects (mean age 53 years, 59% male) and 66,875 control subjects. After adjusting for covariates, overdose that occurred on the index date was strongly associated with CVD [odds ratio (OR), 2.9; 95% confidence interval (CI), 2.4–3.5], especially for arrhythmia (OR, 8.6; 95% CI, 6.2–12.0), ischemic stroke (OR, 5.3; 95% CI, 2.0–14.1), hemorrhagic stroke (OR, 3.1; 95% CI, 1.2–8.3), and myocardial infarction (OR, 3.0; 95% CI, 1.5–5.8). The CVD risk was decreased but remained significantly elevated for overdose that occurred on the previous day, and was not observed for overdose that occurred on each of the previous 2–5 days. Drug overdose appears to be associated with increased risk of cardiovascular diseases.