Individual data from 20 studies including 469 unique patients all undergoing MMA surgery for OSA were extracted [9, 20, 21, 27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43]. Studies included for analysis were published from 2008 to 2023 and originated from eight different countries. All studies included in this review were level 4 Oxford Level of Evidence. The JBI critical appraisal indicated an overall acceptable low risk of bias for all case-series (Appendix 4). A funnel plot (Appendix 5) with Egger’s test (74.1%, 95% CI: 59.8 to 83.3; p =.59) suggested little publication bias. Of the 13 studies that reported BMI values, the ΔBMI was found to be 0.4 (95% CI: -0.2 to 0.9; p =.17). Out of 469 patients, 52.4% (95% CI: 24.5 to 79.5) were Caucasian, 46.0% (95% CI: 19.0 to 74.4) were Asian, and 1.8% (95% CI: 0.8 to 3.5) were of Latino origin. The mean patient age was 40.0 years (range: 18–67, 95% CI: 38.0 to 42.1). Male and female distribution across all 20 studies was 83.1% (95% CI: 76.0 to 89.3) and 16.9% (95% CI: 10.7 to 24.0) respectively. The mean follow-up time for post operative studies was 8.0 months (range: 1.0–24.0 months) [9, 21, 27,28,29,30,31,32,33,34,35,36,37,38, 40,41,42,43]. The overall surgical success was 88.1% which was either reported in the study or was calculated using individual patient data [9, 20, 29, 30, 33, 35,36,37,38,39,40,41, 43]. For the Caucasian, Asian, and Latino groups, surgical success was 83.2%, 93.5%, and 100.0% respectively. The mean follow-up time for post operative studies was 8.0 months (range: 1.0–24.0 months) [9, 21, 27,28,29,30,31,32,33,34,35,36,37,38, 40,41,42,43]. The overall surgical success was 88.1% which was either reported in the study or was calculated using individual patient data [9, 20, 29, 30, 33, 35,36,37,38,39,40,41, 43]. For the Caucasian, Asian, and Latino groups, surgical success was 83.2%, 93.5%, and 100.0% respectively. Among 11 studies, the overall mean maxillary advancement was 5.6 mm (95% CI: 3.9 to 7.5). For Caucasians, it was 7.1 mm (95% CI: 5.2 to 9.0) [20, 29, 31, 33, 38, 39], and for Asians, was 3.7 mm (95% CI: 1.5 to 5.9) [32, 35, 41,42,43]. Maxillary advancement in Caucasians was significantly greater than Asians (p = .02). Among the same 11 studies, the overall mean mandibular advancement was 10.1 mm (95% CI: 8.8 to 11.4). For Caucasians, it was 9.9 mm (95% CI: 7.9 to 11.8) [20, 29, 31, 33, 38, 39], and for Asians, was 10.5 mm (95% CI: 8.6 to 12.3) [32, 35, 41,42,43], with no significant difference in mandibular advancement between them (p = .66). There was no maxillary or mandibular advancement data for the Latino group. A summary of patient characteristics and included studies can be found in Table 1.

For AHI outcomes, ten studies evaluated Caucasian patients [9, 20, 27,28,29, 31, 33, 36,39,40], nine evaluated Asian patients [9, 30, 34,35,36,37, 41,42,43], and one evaluated Latino patients [9]. A meta-analysis was conducted to assess the mean difference (Δ) in AHI between pre-MMA and post-MMA surgeries. The overall group exhibited a significant improvement, with a ΔAHI of -39.6 (95% CI: -49.4 to -29.8; p <.001). The ΔAHI was − 39.6 (95% CI: -55.0 to -24.1; p <.00001) for the Caucasian group, -42.7 (p <.00001) for the Asian group, and − 21.2 (95% CI: -37.7 to -4.6; p =.01) for the Latino group (Fig. 1). All racial groups demonstrated significant improvements in AHI scores, both individually and as a collective group. However, Asians showed greater AHI percent reduction (p <.001) compared to Caucasians and Latinos (Table 2).

When comparing AHI among ethnic/racial groups, there was an overall significant difference (p <.0001) in AHI values between at least two racial groups (Table 2). Further multiple comparisons between groups showed that the mean change (Δ) in AHI was greater in Asians vs. Caucasians at Δ -16.9 (95% CI: -20.4 to -13.3; p <.0001). Lastly, Asians had a lower (better) post-operative AHI value by -3.4 (95% CI: -5.2 to -1.6; p <.0001) compared to Caucasians.