Identifying Those Whom Health Promotion Hardly Reaches: A Systematic Review

To understand what circumstances lend groups to be recognized as hardly reached by health services and research, we systematically reviewed studies that identified their priority populations as hard to reach. We classified attributes of hardly reached groups into cultural/environmental, individual, and demographic domains. Of the 334 identified studies, 78.74% used attributes that were classified into the cultural/environmental, 74.85% the individual, and 50% the demographic domain to identify those hardly reached. Of all possible combinations of domains, the most common was the use of all three domains (28.74%). Overall, papers were more likely to use attributes to identify their hardly reached population that fell into more than one domain (74.85%) compared to only one domain (25.15%; (2), p < .0001). Through this review, we identified the attributes of those who have been identified as hardly reached in published research. No single attribute is used to identify those who are hardly reached. This reflects a socioecological perspective, emphasizing that both intrapersonal and external elements may cause interventions to fail to reach those intended. Moreover, the focus not on populations hardly reached but on the attributes of those hardly reached suggests objectives for interventions to reach them better.