Regional differences in birth prevalence of congenital heart disease in Malta

Recent studies have shown a correlation between environmental pollutants and increased risk of selected congenital malformations. The South-East area of the Island of Malta is much more industrialised than the more rural North-West area. The aim of this study was to test the null hypothesis that there are no regional differences in Malta in the prevalence at birth of congenital cardiac malformations.

Live born infants with congenital cardiac malformations born between 1990 and 1994 were allocated to 10 areas, and thence to 2 regions of 5 areas each, so as to constitute North-West and South-East Malta. Official publications gave population totals and growth rates. Those infants with congenital cardiac malformations were then compared between the different regions using chi2 and the Mann-Whitney U test.

The overall prevalence of congenital heart disease at birth was 8.8/1000 live births. The birth prevalence for the South-East region (10.1/1000 LB--95% CI 8.4-12.3/1000 live births) was significantly higher than for the North-West (7.4/1000 live births--95% CI 6.0-9.0/1000 live births)--p=0.03, Odds ratio 1.38 (95% CI 1.05-1.80). The Mann-Whitney U test showed a significant difference in the distribution amongst the 10 defined areas (p=0.016). The Central-East area had the highest prevalence of cardiac malformations in the entire Island--p=0.02, Odds ratio 1.70 (95% CI 1.10-2.61). Demography showed an efflux of individuals from the South-East of Malta.

The higher prevalence of congenital heart disease noted at birth in South-East Malta is unlikely to be due to genetic factors, as these would have migrated North-West along with the population movement. An environmental factor, therefore, seems more likely to be responsible for the increased predisposition to congenital heart disease in the South-East of Malta.