Familial Aggregation and Heritability of Congenital Heart Defects.

BACKGROUND: Congenital heart defects (CHD) are known to cluster within families, but existing evidence varies for the estimates of familial relative risk (RR). We aimed to examine familial aggregation and heritability of CHD in the general population of Taiwan.Methods and Results:We conducted a population-based family study using the Taiwan National Health Insurance (NHI) research database. Individuals with affected first-degree (n=295,636) or second-degree (n=73,985) relatives were identified from all NHI beneficiaries (n=23,422,955) registered in 2012. Diagnoses of CHD for all study subjects were ascertained between January 1, 1996 and December 31, 2012. Having a twin, a first-degree relative and an affected second-degree relative were associated with an adjusted RR of 12.03 (11.59-12.49), 4.91 (4.85-4.97) and 1.21 (1.14-1.28) for CHD, respectively. Individuals with 1 affected first-degree relative had a RR of 4.78 (4.72-4.84), and those with ≥2 had an RR of 7.10 (6.77-7.45) for CHD. The estimated accountability for phenotypic variance of CHD was 37.3% for familial transmission and 62.8% for non-shared environmental factors. CONCLUSIONS: Our results indicated that CHD tend to cluster within families, and approximately one-third of phenotypic variance was explained by familial factors.

Familial Aggregation and Heritability of Schizophrenia and Co-aggregation of Psychiatric Illnesses in Affected Families.

Strong familial aggregation of schizophrenia has been reported but there is uncertainty concerning the degree of genetic contribution to the phenotypic variance of the disease. This study aimed to examine the familial aggregation and heritability of schizophrenia, and the relative risks (RRs) of other psychiatric diseases, in relatives of people with schizophrenia using the Taiwan National Health Insurance Database. The study population included individuals with affected first-degree or second-degree relatives identified from all beneficiaries (n = 23 422 955) registered in 2013. Diagnoses of schizophrenia made by psychiatrists were ascertained between January 1, 1996 and December 31, 2013. Having an affected co-twin, first-degree relative, second-degree relative, or spouse was associated with an adjusted RR (95% CI) of 37.86 (30.55-46.92), 6.30 (6.09-6.53), 2.44 (1.91-3.12), and 1.88 (1.64-2.15), respectively. Compared with the general population, individuals with one affected first-degree relative had a RR (95% CI) of 6.00 (5.79-6.22) and those with 2 or more had a RR (95% CI) of 14.66 (13.00-16.53) for schizophrenia. The accountability for the phenotypic variance of schizophrenia was 47.3% for genetic factors, 15.5% for shared environmental factors, and 37.2% for non-shared environmental factors. The RR (95% CI) in individuals with a first-degree relative with schizophrenia was 3.49 (3.34-3.64) for mood disorders and 3.91 (3.35-4.57) for delusional disorders. A family history of schizophrenia is therefore associated with a higher risk of developing schizophrenia, mood disorders, and delusional disorders. Heritability and environmental factors each account for half of the phenotypic variance of schizophrenia.