We propose to take advantage of Norway's population-based health registers to investigate risk factors for congenital heart diseases (CHD) in Norway. Epidemiological studies of CHD have never been undertaken on a national level due to lack of data. Such studies are important, because CHD are common among the births defects, the etiology is largely unknown, and the burden imposed on these patients, their families, and society at large is considerable.
All individuals born in Norway from January 1994-Dece mber 2007 will be included in our study cohort. We expect to identify 840,000 births in the Medical Birth Register of Norway (MBR) and 8,400 individuals with CHD, retrieved from the Cardiovascular Disease in Norway Project (CVDNOR), the Cause of Death Reg ister and MBR. The CVDNOR cover all hospital admission for cardiovascular diseases and diabetes in Norway, 1994-2007. By combining codes for heart defects (International Classification of Diseases) in a hierarchical manner, individuals with CHD will be cl assified into heart phenotypes. A subset of cases will be validated against hospital records. Risk factor variables and information on family history of CHD will be obtained from MBR and Highest attained educational register.
CHD prevalence will be evalu ated by time, place and sex, and in an age-, period- and cohort analysis. The associations between maternal, pregnancy-related, socio-economic factors and CHD risk will be estimated as relative risks. Combined effects of risk factors will also be analyzed . And, finally, familial clustering of CHD will be evaluated using recurrence risk ratios, comparing the risk of CHD in individuals with a CHD family history with the risk in individuals without such family history. Relative risks and recurrence risk rati os will be estimated by binominal log-linear regression.
Our goal is to identify risk factors, e.g. folic acid intake, that could implement prevention strategies to reduce CHD in the population.