title: Participation dynamics of a cohort of drug users in a low-threshold methadone treatment programme.
abstract: BACKGROUND
  The low-threshold methadone maintenance treatment (MMT) programme in Hong Kong has been in place for about 40 years. Assessment of the participation pattern of methadone users may inform future programme development to achieve effective harm reduction.
  
  
  METHODS
  Longitudinal clinical data of methadone users who first registered for MMT in the year 2008 in Hong Kong were retrieved after ethical and institutional approval. Participation pattern of this cohort was evaluated by examining users' frequency of attendance and then the overall retention rate. A subgroup of consistent users who remained on treatment in 2012 and/or 2013 was analysed. Comparison was made between high- and low-frequency users, and among high/moderate and low consistency users, to test their correlations with socio-demographics and social connectivity.
  
  
  RESULTS
  The cohort of methadone users registering in the year 2008 was composed of 351 persons, 77 % of whom were ethnic Chinese, with a median age of 34 and the duration of heroin dependency of 6 years. The participation pattern of methadone users was highly variable, with a 6-year retention rate of 38 %. Discontinuations or 'breaks' of >28 days had occurred in 212 (60 %) methadone users. About one third (n = 117) were high-frequency users who had attended more than twice a week for at least 90 % of their treatment periods. The dosages received by high-frequency users were generally higher. Of those continuing on treatment in the fifth and/or sixth year (n = 185), 30 (16 %), 29 (16 %) and 126 (68 %) gave a high, moderate and low level of consistency as defined by the lengths of breaks. High/moderate consistency users had a longer history of heroin use and a higher degree of connectivity with other users by social network analysis.
  
  
  CONCLUSIONS
  Despite the variability of frequency and consistency of attendance of drug users enrolling in the low-threshold MMT programme in Hong Kong, a consistent pattern could be seen in the proportional distribution of dosage and participation efforts. Whereas an adequate dosage was a potential predictor of optimal frequency of attendance, demographics and connectivity had varied between continued users with different levels of consistency.
authors.affiliation: Jockey Club School of Public Health and Primary Care, The Chinese University of Hong Kong, Shatin, Hong Kong. kwantszho@gmail.com.
authors.forename: Tsz Ho
authors.initials: TH
authors.lastname: Kwan
authors.affiliation: Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Shatin, Hong Kong. iseewong@gmail.com.
authors.forename: Ngai Sze
authors.initials: NS
authors.lastname: Wong
authors.affiliation: Stanley Ho Centre for Emerging Infectious Diseases, The Chinese University of Hong Kong, Shatin, Hong Kong. sslee@cuhk.edu.hk.
authors.forename: Shui Shan
authors.initials: SS
authors.lastname: Lee
mesh_terms: D000328:Adult; D015331:Cohort Studies; D055030:Drug Users / Q000706:statistics & numerical data*; D005260:Female; D040261:Harm Reduction; D006556:Heroin Dependence / Q000453:epidemiology / Q000534:rehabilitation*; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008691:Methadone / Q000627:therapeutic use*; D009294:Narcotics / Q000627:therapeutic use; D058850:Opiate Substitution Treatment / Q000706:statistics & numerical data*; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D015819:Substance Abuse, Intravenous / Q000453:epidemiology / Q000534:rehabilitation*
chemical_list: D009294:Narcotics; D008691:Methadone