The physical and mental health of substance misuse patients: A cross-sectional prevalence study in an inner city population

Problem

The treatment of opiate dependency is an important feature of inner city primary care. Several RCTs support methadone replacement as an effective means for harm reduction. There are reports of poor physical health in this group. Mortality rates are over 12 times that of the general population. There have been few studies of long-term conditions (LTCs) in these patients.

Approach

We conducted a cross sectional prevalence study using an anonymised patient-level primary care database, Lambeth DataNet (LDN). We identified all patients prescribed methadone in primary care in the last year. Exclusion criteria: under 25 years; prescribed buprenorphine (because of uncertainty about the prescribing indication); prescribed methadone by community drug teams (since these records could not be linked to primary care data). Demographic, smoking, alcohol and LTC data were extracted. Differences between methadone and non-methadone users were explored with multivariable analysis.

Findings

LDN contained data on 261,749 patients ≥25 years; 422 (0.16%) were prescribed methadone; 969 (0.4%) patients were excluded on the basis of buprenorphine prescription. Patients prescribed methadone were more likely to be male (65.6% vs 49.8%), older (46.1yrs vs 43.4yrs) and less likely to be from an ethnic minority group (South Asian 2.1% vs 5.3%; African Caribbean 5.9% vs 18.6%). Almost all those prescribed methadone were smokers or ex-smokers (97.7% vs 58.5%); more were non-alcohol drinkers (43.2% vs 27.9%). We found a high prevalence of COPD (9.7% vs 1.4%), asthma (17.5% vs 5.8%), depression (32.3% vs 10.1%), serious mental illness (6.6% vs 1.7%), DVT (8.0% vs 0.7%), PE (1.7% vs 0.4%), HIV (4.5% vs 1.1%), hepatitis C (30.0% vs 0.4%) and hepatitis B (2.1% vs 0.1%). Risk of COPD, adjusted for age, gender, ethnicity and deprivation, was raised in smokers: Odds Ratio 8.48 (95%CI 7.78, 9.25), and in the methadone group: OR 4.89 (95%CI: 3.46, 6.90). Even after adjusting for smoking intensity (number of cigarettes/day), the risk was raised in methadone group: OR 3.92 (95%CI: 2.63, 5.85).

Consequences

Regression modelling suggested that methadone as a ‘risk factor’ was independently associated with COPD prevalence, even after adjustment for smoking. The association may be related to unexplored aspects of smoking (such as ‘number of pack-years smoked’) or may be related to other exposures linked with methadone use, such as smoking heroin or crack cocaine. High rates of physical morbidity in patients treated for opiate dependence highlight the need for generalist medical care. Further work is needed to determine the extent to which physical health care is optimised in these patients, both for those receiving methadone medication in primary care and from local community drug teams.