Table 3 Exposure and outcome assessment of included studies by year and author

Gilliland et al., 2003 [45]

Not overweight: ≤85th% vs. Overweight: >85th%;

New-onset physician diagnosed Asthma (child-report)

Age, sex, race, health insurance, community, parental history of asthma/allergies, birth weight, humidifier use, wheeze, allergy, team sports participation, smoking, household ETS, household pets and pests, puberty, and lung function

Sex

Cox proportional hazards

Not obese: ≤95th% vs. obese: >95th%

Gold et al., 2003 [46]

BMI by Z-score

New-onset doctor diagnosed Asthma with wheeze (parental-report)

Maternal smoking, air conditioner use, city of residence, child’s exact age, parental education level, single-parent household, only child status, and race

Sex, race, maternal smoking, age

Cox proportional hazards from BMI Z-score modeled as a time-dependent variable

BMI by Quintile

annual updated BMI Z-scores included as a time-dependent variable

Mamun et al., 2007 [47]

BMI by Z-score at age 5 and 14 years

Asthma at ages 5 years (maternal-report) and age 14 years (self-report)

Sex

One-way ANOVA and F-test used for association between BMI and asthma; logistic regression

Mannino et al., 2006 [48]

Underweight: <25th%

New-onset asthma that limited child’s activity or required the use of medication or frequent attention from a doctor (parental-report)

Race/ethnicity, sex, poverty status, birthweight, and prenatal maternal smoking

Sex

Cox proportional hazards models

Normal weight: 25th-84th%

Overweight/obese: ≥85th%

Zhang et al., 2010 [49]

Age 3 years:

Incident asthma at age 6 years

Breast-feeding, sex, self-reported maternal asthma, dog and cat in household at birth, smoke exposure, day care attendance, having older children in household, and wheezing with rhinovirus infection.

Asthma at 6 years old, asthma at 8 years old

Logistic regression

Low weight: <15th%

Average weight: 15th-84th%

High weight: >85th%

Age 5 years:

Incident asthma at age 8 years

Low weight: <15th%

Average weight: 15th-84th%

High weight: >85th%

Ho et al., 2011 [50]

Underweight

New-onset physician diagnosed Asthma (self-report and parental-report)

Exercise, parental asthma, parental education, breastfeeding, air-conditioning usage, cigarette smoking, ETS, pet(s), and fungus/mold in the home

Sex

Mantel-Haenszel chi-square; Multivariable logistic regression

Normal weight

Overweight

Obese