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Pubertal development in The Netherlands 1965-1997

We investigated pubertal development of 4019 boys and 3562 girls >8 y of age participating in a cross-sectional survey in The Netherlands and compared the results with those of two previous surveys. Reference curves for all pubertal stages were constructed. The 50th percentile of Tanner breast stage 2 was 10.7 y, and 50% of the boys had reached a testicular volume of 4 mL at 11.5 y of age. Median age at menarche was 13.15 y. The median age at which the various stages of pubertal development were observed has stabilized since 1980. The increase of the age at stage G2 between 1965 and 1997 is probably owing to different interpretations of its definition. The current age limits for the definition of precocious are close to the third percentile of these references. A high agreement was found between the pubic hair stages and stages of pubertal (genital and breast) development, but slightly more in boys than in girls. Menarcheal age was dependent on height, weight, and body mass index. At a given age tall or heavy girls have a higher probability of having menarche compared with short or thin girls. A body weight exceeding 60 kg (+1 SDS), or a body mass index of >20 (+1 SDS), has no or little effect on the chance of having menarche, whereas for height such a ceiling effect was not observed. In conclusion, in The Netherlands the age at onset of puberty or menarche has stabilized since 1980. Height, weight, and body mass index have a strong influence on the chance of menarche

Continuous admission to primary school and mental health problems

Background: Younger children in a school class have higher rates of mental health problems if admission to primary school occurs once a year. This study examines whether this relative age effect also occurs if children are admitted to school continuously throughout the year. Methods: We assessed mental health problems based on parent-reports (using the Child Behavior Checklist, CBCL) and on professional assessments, among two Dutch national samples of in total 12,221 children aged 5-15 years (response rate: 86.9%). Results: At ages 5-6, we found a higher occurrence of mental health problems in relatively young children, both for mean CBCL scores (p = 0.017) and for problems assessed by child health professionals (p < 0.0001). At ages 7-15, differences by relative age did not reach statistical significance. Conclusion: Continuous admission to primary school does not prevent mental health problems among young children, but may do so at older ages. Its potential for the prevention of mental problems deserves further study