The MRC BRIGHT study: Demographic and biochemical characteristics of the sibling-pair resource by Munroe, P, Dobson, R, Pembroke, J, Wilson, S, Pheby, J, Colville-Stewart, S, Gilmour, K, Macdade, M, Picton, D, Hussein, J, Dominiczak, A, Brown, M, Samani, N, Clayton, D, Ratcliffe, P, Lathrop, M, Webster, J, Benjamin, N, Farrall, M, Connel, J, Caulfield, M