Table 2 Cohort characteristics of included studies by year and author

Gilliland et al., 2003 [45]

3792;

4th, 7th, and 10th grade public school, asthma-free students (aged 7–18 years)

Annually from 1993–1998 (4 years) or until high school graduation

288 developed asthma during follow-up; 58.1% Caucasian, 28.4% Hispanic, 4.8% Black, 5.6% Asian, 3.1% other; 24.2% overweight at baseline; 10.4% obese at baseline

Girls: N = 1993

Boys: N = 1799

Gold et al., 2003 [46]

9828;

U.S. Six-City Study: children aged 6–14 years

Annually from 1974–1979 (5–7 years)

90% were age 10 or younger at baseline; 3.4% of whites developed asthma with any wheeze during follow-up; 4.7% of blacks developed asthma with any wheeze during follow-up

Girls: N = 4858

Boys: N = 4970

Mamun et al., 2007 [47]

2812;

Australian birth cohort of 7223 mothers and children enrolled from 1981–1984; used 2812 child participants who had complete BMI and asthma at ages 5 and 14 years

Birth cohort assessed at first antenatal clinic visit between 1981–1984, 3–5 days post delivery, 6 months after birth, 5 and 14 years after birth

Mean BMI at age 5 years was 20.64; 8.13% had asthma at age 5 years; 22.28% had asthma in last 6 months at age 14 years

Girls: N = 1340

Boys: N = 1472

Mannino et al., 2006 [48]

4393;

U.S. Children born to women in the National Longitudinal Survey of Youth who first entered the cohort prior to age 2 years and were asthma-free at enrollment

14 years; 1986–2000; data collected every 2 years

218 developed asthma during follow-up; median age for asthma 7.6 years; 55.3% Caucasian, 25.6% Hispanic, 19.1% Black; 33.1% overweight at baseline

Girls: N = 2218

Boys: N = 2175

Zhang et al., 2010 [49]

259;

High-risk full-term newborns (birthweight > 2000 g) with at least 1 asthmatic/atopic parent

Nov 1998 - May 2000

56.4% male and 43.6% female; 86.8% Caucasian and 13.2% ethnic minority; 22% overweight at age 3 years

Girls: N = 112 at 6 yrs;

Boys: N = 147 at 6 yrs;

238;

Girls N = 103 at 8 yrs; Boys N = 135 at 8 yrs

Ho et al., 2011 [50]

4052;

Taiwanese adolescents with pre-asthmatic symptoms selected by non-physician staff from a cohort of 9546

12 month follow-up 1995-1996

10.9% boys and 14.1% girls developed asthma during follow-up; 13.0% overweight at baseline; 12.0% obese at baseline

Girls: N = 1846

Boys: N = 2206