Modest familial risks for MS: a registry-based study of the population of Sweden
This large Swedish study included 28,396 MS patients identified through the Swedish MS registry and a nationwide hospital registry. First and second degree relatives and cousins were also identified through the national Multi-Generation Registry, while the Swedish Twin Registry was used to identify twins of patients with MS.
The researchers linked the medical registries to the population registries in Sweden, and therefore controlled for differences in prevalence throughout time and between groups. Using matched population-based controls, the relative risks were calculated, which demonstrated lower estimates of familial MS risks than previously reported.
Interestingly, despite the well known lower prevalence of MS among males, the relative risks were equal among maternal and paternal relations. A higher transmission rate from father to son than from mother to son was seen, indicating a higher transmission to offspring from the less prevalent sex.
The heritability of MS in twin pairs with known zygosity was estimated to be 0.64. These results raise the possibility that the familial relative risks may be lower than previously reported.
: Westerlind H, Ramanujam R
Brain. 2014 Jan 17. [Epub ahead of print]
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