Background and aims: Most people who use heroin also smoke tobacco, but there is limited investment to reduce the prevalence of smoking in this group. This may be due to a perception that tobacco is less harmful than other substances and is a lower priority problem. Among people who use heroin in England, we aimed to compare tobacco smoking and illegal drugs in terms of the risk of premature death and years-of-life lost.

Design: Period life-tables based on age- and cause-specific mortality rates. We included six causes of death: (1) smoking-specific diseases: respiratory cancers and chronic obstructive pulmonary disease, (2) other cancers, (3) cardiovascular diseases, (4) drug poisoning, (5) viral hepatitis and (6) all other causes. We attributed fractions of these deaths to tobacco smoking and illegal drugs.

Setting: England, 2000–2018.

Participants: 106 789 people who use illegal opioids, drawn from the Clinical Practice Research Datalink (CPRD).

Measurements: (1) Risk of premature death (before age 70), (2) the proportion of premature deaths attributable to smoking and illegal drugs, (3) the potential reduction in premature deaths by eliminating tobacco and/or illegal drugs. We also estimated years-of-life lost in these scenarios, which gives greater weight to deaths at younger ages.

Findings: We estimated that 63.2% [95% confidence interval (CI) = 62.2–64.1] of people who use heroin would die before age 70, compared with 16.2% of the general population. Among people who use heroin, we attributed 23.6% (95% CI = 22.8–24.5) of premature deaths to tobacco smoking and 27.6% (95% CI = 26.7–28.6) to illegal drugs. Elimination of tobacco smoking would have reduced the risk of premature death by 11.8 (95% CI = 10.5–13.1) percentage points to 51.5% (95% CI = 50.6–52.4), while elimination of illegal drugs would have reduced the risk of premature death by 9.4 (95% CI = 7.8–11.0) percentage points to 53.9% (95% CI = 52.7–55.1). Drug-related deaths typically happened at a younger age than smoking-related deaths. Therefore, the years-of-life lost attributable to illegal drugs (mean per person 4.94 years; 95% CI = 4.71–5.17) were approximately three times greater than for tobacco (mean per person 1.68 years; 95% CI = 1.62–1.75).

Conclusions: Tobacco smoking and illegal drugs each appear to account for around one-quarter of premature deaths among people who use heroin.