Cause-specific hospitalisation and death in a cohort of people who use heroin and crack cocaine in London, England: the importance of non-communicable diseases, skin infections, head injuries and dental caries
Background: Research into health outcomes and healthcare interventions for people who use heroin and crack cocaine has focused on blood-borne viral infections, overdose, and serious mental health problems. This is partly because these outcomes are rare in the general population and therefore the relative risks associated with drug use are large. Common non-communicable diseases such as cardiovascular disease, respiratory disease and cancer have received less attention. We considered relative and absolute risks of hospitalisation and death across a full range of diseases.
Methods: We studied a cohort study of 7844 people who have received treatment for heroin or crack cocaine dependence in London, England, with linkage to national hospital admissions and mortality data over mean 6.5 years of follow-up. Mean age at baseline was 37.3 (sd 9.0) and 74% were male. We counted hospitalisations and deaths for 59 disease groups, based on ICD10 codes for the primary cause of admission and the underlying cause of death. Expected numbers of hospitalisations and deaths were calculated using age- and sex-specific rates from the general population of London. Standardised rate ratios (standardised mortality ratio or SMR for deaths; standardised admission ratio or SAR for hospitalisations) and the number of attributable (or 'excess') events were compared.
Results: There were 25211 hospital admissions, giving a crude admission rate of 49 per 100 person-years and an all-cause SAR of 3.1. The highest SARs were for intoxication, dependence or withdrawal (838); psychiatric disorders (223); drug poisoning (141); and liver disease (27). There were 17137 excess hospitalisations, of which the largest contributors were intoxication, dependence or withdrawal (3245); drug poisonings (1469); skin infections (1111); COPD (834); head injury (721); and dental caries (635). There were 679 deaths, giving a crude mortality rate of 13.3 per 1000 person-years and an all-cause SMR of 7.3. The highest SMRs were for drug poisonings (70); viral hepatitis (45); COPD (21); and HIV (17). There were 591 excess deaths, of which the largest contributors were drug poisonings (228); liver disease (83); cardiovascular diseases (46); COPD (39); and accidents (33). When the 59 disease groups were collapsed into drug-related and non-drug-related causes, 20% of excess hospital admissions and 39% of excess deaths had a primary drug-related cause.
Conclusions: Health outcomes in this cohort were poor, with an all-cause SMR comparable to published data from cohorts of people who have received opiate substitution. The data highlight the importance of non-communicable diseases, skin infections, head injuries and dental caries. There are few interventions to improve prevention, detection and treatment of these problems in people who use heroin and crack, and research is needed.