The geography of the community sex ratios for young children in Newfoundland

Abstract Abnormalities of the sex ratio of births may be linked with environmental factors, including diet and pollutants in the general or occupational environments, which in turn can cause ill-health. To examine this relationship in the Province of Newfoundland and Labrador, where a geographical imbalance of mortality has already been identified, we examined the geographical distribution of sex ratios (boys/girls × 100) of young children (0–4 years) in the communities of the Province during recent years. The individual communities of the 1976 and 1981 censuses were assigned to contiguous regions and their component districts. The numbers in the appropriate age-groups in the communities in these two census years were used to calculate a mean sex ratio for each community; each community was allocated, according to the value of its ratio, to one of four predefined categories of ratio. From the numbers of communities belonging to these various categories of sex ratio in the regions and districts, the community sex ratios of these areas (i.e. regions and districts) were derived. As a preliminary assessment of the relationship between sex ratios and mortality, a small group of communities with the highest sex ratios was selected, and the mean standardized mortality ratios (SMRs) for all deaths in those communities were calculated. The community sex ratios of regions and districts declined from east to west. The difference in the ratios between the Avalon region (in the most easterly part of the Province) and the southwest region was statistically significant. Districts with high ratios were frequent, particularly those on the Avalon peninsula in the south-east of the island, whereas low ratios were more frequent on the south-west coast of the island, and a low ratio was also found for the only inland district. Of the communities with statistically reliable numbers, the township of Makkovik in Labrador had the highest sex ratio (100 × 50/25 = 200). The SMR of that community during 1976–1982 was statistically elevated at 218. In the small group of communities studied, however, high sex ratios from census data for individual communities were not reliable predictors of high SMRs. Further work is required to clarify the inter-relationships between the sex ratios of the census data, the sex ratios of births, the mortality rates and environmental factors.