The search identified 36,561 titles and abstracts. After removing duplicates, the remaining 29,036 titles and abstracts were screened for potential inclusion. Following initial screening there were 656 full-texts reviewed, which identified a total of 39 studies [42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80] which met the inclusion criteria (see Fig. 1).

Fifteen of the included studies (41%) were randomised controlled trials [44, 50, 56, 57, 59, 61,62,63,64,65,66,67, 74, 77, 80] with the other quantitative designs including non-randomised experimental [60, 69], pre-post [67, 75, 78, 79], cohort, cross-sectional [42, 43, 71] and feasibility/pilot studies [45, 47, 49, 52,53,54, 58]. Seven studies (19%) utilised only qualitative designs, including focus groups [70, 72], interviews [51, 55, 76], and a mixture of both [46, 48]. Seventy per cent (n = 27) of all studies were conducted in the United States [43,44,45, 47,48,49,50, 54, 56,57,58,59,60,61,62,63,64, 66, 67, 71,72,73, 75, 77,78,79,80] with the remaining undertaken in England [42, 65, 76], Australia [67, 70], Norway [46, 55], Scotland [52, 74], Wales [51], Finland [69] and Switzerland [53]. Within the studies, the intervention sample sizes ranged from 10 to 2818. The mean age ranged from 31.5 to 72.9 years. Intervention studies mostly included participants with a mean age between 40 and 49 years (n = 14) [42, 44, 56, 59, 62,63,64, 68, 69, 73,74,75, 77, 80] and 50 and 64 years (n = 12) [45, 50, 54, 57, 58, 60, 61, 65,66,67, 78] with a few studies targeting younger (mean age 20–40 years) [79] and older (mean age of >65 years) cohorts [47, 49, 52].

Participants’ ethnicity varied across studies; however, it is important to note that ethnicity was not reported for eleven (30%) of the articles included [46, 48,