The fifth wave of data collection of the Finntwin16 cohort was done in May 2010 (a pilot study), October 2010 to November 2011 for Finnish speaking subjects and in the spring of 2012 for Swedish speaking subjects. The cohort has over 3,000 twin pairs, and the invitation was sent to all twins living in Finland irrespective of earlier participation. Twins who had indicated that they no longer wished to participate were naturally not contacted. Of the 6,132 twins that we contacted, 4,414 participated, a response rate of 72%.
