Recruitment and characteristics of participants in trials of physical activity for adults aged 45 years and above in general practice: a systematic review

BACKGROUND: General practice is well situated to promote physical activity (PA), but with PA levels declining after 45 years of age, often those who are most likely to benefit from interventions tend to be the least likely recruited to participate in research. AIMS AND RATIONALE: The aim of this study was to investigate recruitment and reporting of participant demographics in PA trials for adults aged 45 years and above. Specific objectives were: (i) to examine the reporting of demographics of participants; (ii) to investigate the strategies used to recruit these participants; and, (iii) to examine the efficiency of recruitment strategies. METHODS: Seven databases were searched, including: PubMed, CINAHL, the Cochrane Library Register of Controlled Trials, Embase, Scopus, PsycINFO, and Web of Science. Only randomized control trials involving adults 45 years old or older recruited through primary care were included. The PRISMA framework for systematic review was followed, which involved 2 researchers independently conducting title, abstract, and full article screening. Tools for data extraction and synthesis were adapted from previous work on inclusivity in recruitment. RESULTS: The searches retrieved 3,491 studies of which 12 were included for review. Sample size of the studies ranged from 31 to 1,366, with a total of 6,042 participants of which 57% were female. Of 101 participating practices, 1 was reported as rural. Reporting of recruitment lacked detail—only 6 studies outlined how practices were recruited. 11/12 studies involved a database or chart review to identify participants that met the inclusion criteria, followed by a letter of invitation sent to those people. The studies with higher recruitment efficiency ratios each employed more than 1 recruitment strategy, e.g. opportunistic invitations and telephone calls. CONCLUSION: This systematic review has presented deficits in the reporting of both demographics and recruitment. Future research should aim for a standardized approach to reporting.