December 17, 2003
Month of Birth Effect on Height and Weight
American Journal of Human Biology
Volume 16, Issue 1 , Pages 31 - 42
Month-of-birth effect on height and weight in Polish rural children
Krzysztof Kociski et al.
Abstract
This study investigated a hypothesis of dependence of child height and weight on the month of their birth. The sample comprised 1,241 subjects, 568 boys and 673 girls, age 6-20 years, from villages in Olsztyn Province, Northeast Poland. Individuals' height and weight data were standardized by sex and age to allow grouping of individuals born in the same month irrespective of their sex and age at examination. Subjects born in October to March proved to be significantly taller and heavier than those born in April to September. The magnitude of differences between the semiannual groupings equaled 13.1% of a standard deviation (SD) in height (P = 0.03) and 14.2% of SD in weight (P = 0.02). The month-of-birth effect was much stronger for children characterized by high socioeconomic status, where these differences amounted to 39.1% of SD in height (P = 0.02) and 49.4% of SD in weight (P = 0.01). There were no regular changes of the effect with age and no differences between the sexes were found. Fitted cosine functions identified the highest values of examined traits for individuals born in December with the lowest values being found in those born in June. Possible explanations of the month-of-birth effect are considered in terms of age categorizing, seasonal variety of growth rates, as well as birth-related or conception-related global, hemispheric, and local factors. This study rejects the first two possibilities and suggests this effect requires further research to be conducted in various geographical locations, climates, and cultures, on humans as well as on other species.
Posted by Dienekes at December 17, 2003 07:38 PM | PermaLinkThere's a big difference between the city and rural populations in Poland, and between the higher and lower socioeconomic groups.
The former average at over 180cm, while the latter at less than 177cm.
However, the latest (2003) studies by the Polish Army show that Poles are still growing, unlike Scandinavians, who haven't been growing for the past 30 years or so (average 179-181cm).
Posted by: Polak at December 18, 2003 07:08 PMNow I'm sure why I'm so tall, I was born in February! ^^
Well, at least an interesting aspect on environmental influences. The only thing I would question is that the difference is so huge because of only this factor.
But I hope they can determine WHY this factor is important.
What do you guess?
And what would be interesting too is wheter this factor is just important in temperate climates or in the subtropic and tropic regions too.
If not it must have something to do with temperature.
Posted by: Chris at December 20, 2003 07:44 AMI think it's a northern European thing. I think the diet differs in Poland throughout the year, and that has a big effect on height.
Posted by: Polak at December 23, 2003 06:05 PM