Familial aggregation of atrial fibrillation: a study in Danish twins

BACKGROUND: Heritability may play a role in non-familial atrial fibrillation (AF). We hypothesized that a monozygotic (MZ) twin whose co-twin was diagnosed with AF would have an increased risk of the disease compared to a dizygotic (DZ) twin in the same situation. METHODS AND RESULTS: A sample of 1137 same-sex twin pairs (356 MZ and 781 DZ pairs) where one or both members were diagnosed with AF were identified in The Danish Twin Registry. Concordance rates were twice as high for MZ pairs than for DZ pairs regardless of gender, 22.0% vs. 11.6% (p<0.0001). In a Cox regression of event free survival times, we compared the time span between occurrences of disease in MZ and DZ twins. The unaffected twin was included, when his or her twin-sibling (the index twin) was diagnosed with AF. After adjustment for age at entry, MZ twins had a significantly shorter event free survival time (hazard ratio: 2.0 (95% confidence interval (CI): 1.3 – 3.0)) thereby indicating a genetic component. Using biometric models, we estimated the heritability of AF to be 62 % (55 % – 68 %), due to additive genetics. There were no significant differences across genders. CONCLUSION: All the analyses of twin similarities in the present study indicate that genetic factors play a substantial role in the risk of AF for both genders. The recurrence risk for co-twins (12–22%) is clinically relevant and suggests that co-twins of AF-affected twins belong to a high-risk group for AF

Neurotoxicity from prenatal and postnatal exposure to methylmercury

The extent to which postnatal methylmercury exposure contributes to neurobehavioral delays is uncertain. Confounding may occur because the child's dietary exposure likely correlates with the mother's. This conundrum was examined in the Faroese birth cohort 1 born in 1986–1987. Exposure parameters included mercury concentrations in maternal hair at parturition, cord blood, and child blood and hair at the age-7 clinical examination (N = 923). In regression analyses, the child's current blood-mercury at age 7 (N = 694) showed only weak associations with the neuropsychological test variables, but visuospatial memory revealed a significant negative association. Mutual adjustment caused decreases of the apparent effect of the prenatal exposure. However, such adjustment may lead to underestimations due to the presence of correlated, error-prone exposure variables. In structural equation models, all methylmercury exposure parameters were instead entered into a latent exposure variable that reflected the total methylmercury load. This latent exposure showed significant associations with neurodevelopmental deficits, with prenatal exposure providing the main information. However, postnatal methylmercury exposure appeared to contribute to neurotoxic effects, in particular in regard to visuospatial processing and memory. Thus, addition in the regression analysis of exposure information obtained at a different point in time was not informative and should be avoided. Further studies with better information on exposure profiles are needed to characterize the effects of postnatal methylmercury exposure

Serotonin transporter binding in the hypothalamus correlates negatively with tonic heat pain ratings in healthy subjects: A [11C]DASB PET study

status: publishe