Growth status and menarche in urban and rural China

Objective: To examine the relationship between current age at menarche and growth status in an urban and rural area of Eastern China. Study design: Cross-sectional survey: self-completion questionnaire and anthropometry in 12 schools in urban Hangzhou and rural Chunan in Zhejiang Province. Results: The median menarcheal age calculated by probit analysis was significantly different in the two areas: 12.8 years (SD 0.9) in the urban area and 13.2 (SD 1.0) in the rural area (p <0.001). Girls who reach menarche are significantly heavier and taller with higher BMIs than those of the same age who are pre-menarche. After adjustment for BMI and other possible confounders, urban girls were still menstruating significantly earlier than girls in rural areas (OR 3.3, 2.1-5.2). Conclusions: The age of menarche is probably still declining in China. Although BMI is an important factor in the onset of menstruation, some other unmeasured environmental variable may be implicated in this population.