Changes in the injecting risk behaviour of injecting drug users in London, 1990-1993

To describe changes in the injecting risk behaviour of injecting drug users (IDU) in London between 1990 and 1993.

Injecting risk behaviour was measured over 4 years (1990-1993) in a serial point HIV prevalence study of 2062 IDU recruited in both drug treatment and non-treatment community-based settings within greater London. The study used a structured questionnaire and common sampling and interview strategy developed by a World Health Organization technical group and implemented in 13 cities.

Log-linear models were used to assess patterns of change over years and of differences in injecting risk behaviour, including syringe sharing and syringe hygiene between 1990 and 1993. The log likelihood chi 2 statistic, G2, was used to test statistical significance. Changes in the mean values were assessed first using parametric tests assuming normality and the results were compared with Kruskal-Wallis (non-parametric) tests. Pearsons chi 2 was used to measure differences in frequency of sharing occasions and partner selectivity.

An overall reduction in injecting risk behaviour was observed during the first 2 years of this study, including a decline in syringe sharing (both accepting and passing on used syringes), the number of sharing partners and the frequency of sharing occasions. Most sharers restricted sharing to sexual partners and close friends. The majority of sharers reported always cleaning injecting equipment. Main source of sterile equipment was pharmacies and syringe exchanges. Indirect sharing (of spoons, filters, and by front- or backloading) was reported. Since 1991 there has been a stabilization in risk behaviour.

The data indicate that IDU in London have made positive reductions in risk behaviour. Levels of syringe sharing were substantially lower than those reported up to 1987 before AIDS awareness and the introduction of HIV prevention measures. The majority did not share syringes or confined their sharing to close friends and sexual partners, and if shared, cleaned their syringes. Continuation of indirect sharing indicates the need for more detailed prevention messages. While the initial decline in syringe-sharing rates may be attributed to the wide availability of sterile injecting equipment and other preventive measures, it may now be necessary to look beyond current intervention initiatives to develop interventions which seek to change the social etiquette of sharing and move towards the long-term maintenance of low levels of injecting risk behaviour.