Characteristics of the included studies
| Study | Country | Publication year | Study design | Recruitment | N | Age (years) | Male (%) | Gestational age (weeks) | Population |
| Kallio et al28 | Finland | 2010 | Cross-sectional | Recruited as infants in 1990–1992 for the STRIP project | 494 | 13.0 | 52.4 | NA | Healthy children |
| Geerts et al27 | Netherlands | 2012 | Cross-sectional | Recruited as infants in 2001 for the WHISTLER project | 259 | 5.4±0.3 | 43.6 | 39.5±1.4 (mean±SD) | Healthy children |
| Yang et al29 | China | 2011 | Cross-sectional | Recruited through middle schools in Lhasa city | 624 | 16.0 | 100.0 | NA | Healthy adolescents |
| Ayer et al24 | Australia | 2011 | Cross-sectional | Enrolled prior to birth into the CAPS project in1997-1999 | 405 | 8.0 | 49.6 | 39.6 (39.4 to 39.7) (95% CI) | Healthy children |
NA, not available; STRIP, Special Turku Coronary Risk Factor Intervention Project; WHISTLER, the WHeezing Illnesses STudy LEidsche Rijn.