Temporal and spatial trends in the sex ratio at birth in Greece, 1960–2006: exploring potential environmental factors.

Numerous studies have shown that the sex ratio at birth, defined as the relative number of male and female births, may be dramatically lower for small cohorts with high chemical exposures. Meanwhile, reports from different countries have shown recent declines in male births for the general population, perhaps implicating environmental factors. The sex ratio at birth has, therefore, been suggested by some as a sentinel environmental health indicator. This paper examines variation observed in sex ratio at birth in Greece since 1960. The analysis incorporates a number of demographic parameters including the age and nationality of the mother, partnership status and birth order, as well as urbanisation level. The latter is considered an indirect indicator of potential environmental incidence. Our main finding is that the sex ratio in Greece has experienced a slight, albeit statistically significant, downward trend, especially since 1980. Further, this decline is not attributable to changing demographics. Geographical differentiations were found to be quite significant: the sex ratio is significantly higher in rural areas compared to urban centres or Greater Athens, and this difference is increasing over time. We offer a preliminary interpretation suggesting that these temporal and spatial trends may, at least partly, be attributed to chemicals’ exposure due to higher levels of indoor and outdoor air pollution and different consumption habits encountered in urban settings. We argue that such possibilities warrant further research with explicit measures of exposure. [ABSTRACT FROM AUTHOR]