Demographic characteristics of included studies
| Study | Total, n | BIF, n | BIF IQ | Age (yr) | Male (%) |
|---|---|---|---|---|---|
| Água Dias et al. [14], 2019 | 40 | 40 | 71-84 | 10.03 |
60 |
| Alesi et al. [23], 2015 | 104 | 25 | - |
8.8-9.9 | 66.3 |
| Alloway [12], 2010 | 78 | 39 | 70-85 | 7-11 | 69.2 |
| Baglio et al. [31], 2016 | 59 | 28 | 70-85 | 9.46 |
57.1 |
| Barnevik Olsson et al. [46], 2017 | 208 | 50 | 70-84 | 4.5-6.5 | 91.8 |
| Chen et al. [39], 2006 | 1681 | 178 | 70-80 | 27-33 | 45.8 |
| Claypool et al. [19], 2008 | 196 | 59 | 70-79 | 10.9 |
55 |
| Dekker and Koot [38], 2003 | 474 | 367 | 60-80 | 6-18 | 61.8 |
| Emerson et al. [24], 2010 | 4337 | 598 | 70-85 | 6-7 | - |
| Fenning et al. [8], 2007 | 217 | 29 | 71-84 | 5 | 58.1 |
| Fernell and Ek [21], 2010 | 117 | 38 | 70-84 | 16 | 75.2 |
| Galletta et al. [11], 2020 | 55 | 25 | 71-84 | 27.64 |
16 |
| Gigi et al. [3], 2014 | 173542 | 76962 | 71-84 | 16-17 | 100 |
| Hartman et al. [37], 2010 | 194 | 61 | 70-79 | 7-12 | 58.8 |
| Hassiotis et al. [4], 2008 | 8450 | 1040 | 70-84 | 16-74 | - |
| Karande et al. [18], 2008 | 55 | 55 | 71-84 | 8-17 | 63.6 |
| Kortteinen et al. [20], 2009 | 155 | 62 | 71-84 | 8th grade | 33-77 |
| McAlpine et al. [28], 1991 | 511 | 25 | 1 SD below | 5-66 | 48-78 |
| Pulina et al. [9], 2019 | 264 | 204 | 70-85 | 6-15.5 | 67.6 |
| Sätilä et al. [10], 2022 | 651 | - |
70-79 | 5.2-27 | 63 |
| Smirni et al. [15], 2019 | 116 | 65 | 71-84 | 126-13.4 | 50 |
*mean age; †information was not reported. BIF, borderline intellectual functioning; IQ, intelligence quotient; SD, standard deviation