Short-term secular variation in menarche and blood lead concentration in school girls in the Copper Basin of southwestern Poland: 1995 and 2007.

Objectives: To evaluate short-term secular change in menarche and associations with blood lead level in Polish girls between 1995 and 2007.
Methods: Menarcheal status of school girls 7-16 years from villages in southwestern Poland was surveyed in 1995, 2001, 2004, and 2007. Blood lead was sampled in 1995 and 2007. Median ages and variance statistics for menarche were estimated with probit analysis. Associations between blood lead level and menarcheal status in 1995 and 2007 were analyzed with logistic regression using blood lead level as an independent binary variable: 2.00-5.00 and ≥5.10 μg/dl.
Results: Median ages at menarche declined slightly from 1995 (13.36 ± 0.06 years) to 2001 (13.20 ± 0.04 years), was stable in 2004 (13.20 ± 0.05 years), and declined to 2007 (12.81 ± 0.05 years). Blood lead levels declined from 6.57 ± 0.13 μg/dl in 1995 to 4.24 ± 0.14 μg/dl in 2007. With age, height, and BMI controlled, probability of attaining menarche was not associated with blood lead in 1995, but was decreased with increased blood lead in 2007 (OR 0.31, 95% CI 0.09-1.06, P = 0.057).
Conclusion: Ages at menarche and blood lead levels declined between 1995 and 2007. Higher blood lead levels were not associated with menarche in 1995, suggesting that nutritional and health conditions and perhaps somewhat unstable social and economic conditions in the 1980s and early 1990s may have masked the influence of lead on sexual maturation. Elevated blood lead was associated with the probability of later menarche in 2007, although the association was of borderline (P = 0.06).
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