The causes and effects of socio-demographic exclusions from clinical trials

Bartlett C, Doyal L, Ebrahim S, Davey P, Bachmann M, Egger M, Dieppe P
Record ID 32005001175
Authors' objectives:

The aim of this report was to investigate the exclusion from trials of women, older people and minority ethnic groups, focusing on two drug exemplars, statins and non-steroidal anti-inflammatory drugs (NSAIDs).

Authors' results and conclusions: The average age of statins trial participants was 58.5 years; only 16.3% were women. Statins reduced cardiovascular disease (CVD) incidence by about 25% in both men and women. Older people up to 75 years of age also benefited. Meta-analysis and two landmark trials confirmed these results. The average age of NSAIDs trial participants was 61.9 years and women were well represented (68.5%). Gastrointestinal (GI) adverse events were commonly reported, but renal side-effects were not. Outcomes were seldom reported according to socio-demographic group. For both drugs, USA trials were more inclusive than UK/European trials. Ethnicity was not well reported for either drug. Some 23% of the cohort were treated with statins. Users were younger than non-statins users (but no more likely to be male) and had superior outcomes. High current exposure to NSAIDs elevated the risk of GI side-effects by about 50% versus no current exposure and renal impairment risk by nearly 140%. Side-effect risk increased with age; being female diminished risk. Approximately 537,000 incident cases of CVD would qualify for statins use in England each year. Women constitute 45% of this population with need, two-thirds of whom are aged 65 years or over. Need varies by ethnic group. No sex bias in prescribing statins was detected, but use was commoner in younger people. For NSAIDs, 6.3% of adults aged 35+ years reported hip and/or knee pain associated with OA; 3.9% of adults used prescribed analgesics for this and they were more likely to be women and to be >65 years old. For statins, women formed almost half of the 'with need' and 'on treatment' populations, but were markedly under-represented in trials. Those aged 65+ years formed nearly two-thirds of the 'with need' population, but only one-fifth of trial samples, and were less likely to be treated than younger subjects. For NSAIDs, women formed similar proportions. Associations of side-effects with socio-demographic factors was revealed in cohort data but not in trials.
Authors' recommendations: The issue of exclusion from trials of women, older people and ethnic minorities has been relatively neglected in the UK research community, and there is confusion about diversity issues. Under-representation occurs, but in drug trials at least this may not always affect the external validity of relative effect estimates. However, measures of absolute effectiveness, absolute harm and cost-effectiveness are associated with underlying risk levels in different socio-demographic groups. Under-representation will therefore bias absolute effect estimates. The following areas are suggested for future research: multi-disciplinary assessment of realistic options for trialists to address the issue of exclusions; clarification of the use of ethnic categories in health research and of the implications of the different dimensions of ageing and sex/gender; identification of barriers and facilitators to the involvement of different population groups in research, further investigation of the susceptibility of older men to NSAID adverse events, and the development of a 'register of registries and databases' and exploration of how linked health information systems in the UK could be improved.
Authors' methods: Review
Project Status: Completed
Year Published: 2005
English language abstract: An English language summary is available
Publication Type: Not Assigned
Country: England, United Kingdom
MeSH Terms
  • Anticholesteremic Agents
  • Anti-Inflammatory Agents, Non-Steroidal
  • Clinical Trials as Topic
  • Patient Participation
  • Patient Selection
  • Selection Bias
  • Socioeconomic Factors
Organisation Name: NIHR Health Technology Assessment programme
Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK
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Copyright: 2009 Queen's Printer and Controller of HMSO
This is a bibliographic record of a published health technology assessment from a member of INAHTA or other HTA producer. No evaluation of the quality of this assessment has been made for the HTA database.