Declining male births with increasing geographical latitude in Europe

doi:10.1136/jech.54.4.244

Journal of Epidemiology and Community Health 2000;54:244-246; doi:10.1136/jech.54.4.244

J Epidemiol Community Health 2000;54:244-246 ( April )

Research report

Declining male births with increasing geographical latitude in Europe Victor Grech^a, P Vassallo-Agius^c, Charles Savona-Ventura^b

^a Paediatric Department, St Luke's Hospital, Malta, ^b Department of Obstetrics and Gynaecology, St Luke's Hospital, ^c Medical School, University of Malta

Correspondence to: Dr Grech, Paediatric Department, St Luke's Hospital, Guardamangia, Malta

Accepted for publication 4 September 1999

OBJECTIVE $---$ Demographic studies in various industrialised countries have shown a decline in male births in the latter half of the 20thcentury from the expected ratio of 0.515 (males/total). This studyanalyses trends in this ratio over the period 1890 to 1995 inMalta, and also analyses this ratio for Western European countriesfor the period 1990-1995.
DESIGN $---$ Births subdivided by sex were obtained from official Maltese publications. European countries were grouped according to geographicallatitude by banding countries into three groups: Northern Mediterranean,Central European and Scandinavian. Births by sex for these countrieswere also analysed for the period 1990-1995.
RESULTS $---$ No decline in the ratio of male births to total births was noted in Malta over the period 1916-1995. However, the ratio washigher than expected (n=151 766, ratio=0.517(95% confidence intervals(95%CI): 0.514, 0.519). Moreover, during the period 1890-1899(n=66 874), the ratio was 0.523 (95% CI: 0.519, 0.527), even higherthan observed during the 20th century ( $chi$ ²=8.3, p=0.004). Analysis of European births showed a much higherratio of male births in the south of Europe than in the north( $chi$ ²=87.2, p<0.0001).
CONCLUSIONS $---$ The findings were unable to explain the higher incidence of male births in the south of Europe, but it is speculated thatambient temperatures may not only affect fertility, but also influencesex ratios atbirth.

Keywords: sex ratio

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