Changes in shape and location of BMI distributions of Swedish children.

Aims: One aim was to disentangle how the shape and location of the BMI distribution changed among Swedish children over a 12 y period. Another aim was to identify the age during childhood when changes occurred or became manifest.

Methods: Two population-based cohorts-2,591 children from Stockholm born 1985-1987 and 3,650 from Gothenburg born 1973-1975-were compared with respect to BMI distributions from 2 to 15 y of age.

Results: Differences between the BMI distributions of the two cohorts were present from 5-6 y of age. From age 7, the children born in 1985-1987 and belonging to the upper parts of the BMI distribution, e.g. those above the 90th or 95th BMI percentiles, had much higher BMI mean values compared to their counterparts born 12 y earlier. Comparisons with respect to the 5th, 10th, 25th, 50th, 75th, 90th and 95th BMI percentiles showed that changes appeared above the 25th percentile and became increasingly pronounced in the upper parts of the BMI distributions.

Conclusion: School-aged children in the rightmost parts of the BMI distributions may be more susceptible to "obesogenic" environmental exposures than those in the middle or leftmost parts. The results support the suggestion that the period of BMI rebound is critical for the development of obesity.