Table 1.
Characteristics of studies included in the meta-analysis.
| Study | Country | Sample Size Obesity/Control 1 | Gender | Age Interval (years) | Defined Criteria for Obesity | Study Design | Primary Outcome | Quality Score |
|---|---|---|---|---|---|---|---|---|
| Shen 2013 [28] | China | 81/944 | Girls | 7.02–12.02 | BMI ≥ 95th percentile | Cohort | No. of girls that had menarche | 8 |
| Gavela-Pérez 2015 [29] | Spain | 30/118 | Girls | 7.23–14.61 | According to Cole [36] | Cohort | Age at menarche | 8 |
| Zhai 2015 [30] | China | 40/40 | Girls | 8.5–12.5 | Percentage of body fat using skin-fold thickness: ≥25% | Cohort | No. of girls that had menarche No. of girls with breast stage 2 No. of girls with early puberty 2 |
9 |
| Ramezani Tehrani 2014 [31] | Iran | 31/312 | Girls | 12–18 | BMI > 95th percentile | Cohort | Age at menarche | 8 |
| Lee 2007 [11] | US | 5/257 | Girls | 3–12 | BMI ≥ 95th percentile | Cohort | No. of girls with early puberty 3 | 9 |
| Leitao 2013 [32] | Portugal | 20/89 | Girls | 7–15 | ≥30 % body fat | Cohort | No. of girls with early puberty 4 | 9 |
| Tremblay 2005 [33] | Canada | 36/708 | Girls | 11–13 | BMI ≥ 95th percentile | Cohort | No. of girls with early puberty 5 | 8 |
| Davison 2003 [12] | US | 24/101 | Girls | 5–9 | According to 2000 growth charts from the Centers for Disease Control and Prevention [37] | Cohort | No. of girls with early puberty 6 | 7 |
1 Control group: normal-weight group; 2 Early puberty was defined as girls who reached breast stage II earlier than the median age for that stage in China (9.2 years); 3 Early puberty occurred was defined as breast development at or more than breast stage II by physical examination at the grade 4visit (9.6 ± 0.1 years); 4 Early puberty occurred was defined according to age at menarche, <12 years for early menarche, 12–13 years for average menarche, and >13 years for late menarche; 5 Early puberty occurred was defined according to age at menarche, those who are below two standard deviations from their average maturing peers (1.28z to 1.04z)(z=(x-μ)/σ), or 10–15% of the left tail of the normal range distribution based on the age at which they reported having had their first menses. In this study, early menarche averaged 11 years old, on-time pubertal timing averaged 12 years old and late pubertal timing averaged 13 years; 6 Early puberty occurred was defined as girls who fulfilled at least 2 of the following 3 criteria: (1) highest tertile for estradiol; (2) Tanner stage 3 for breast development; and (3) highest tertile for the PDS (Pubertal Development Scale, PDS) at 9 years old.