The NSHD is a representative sample of 5362 males and females who were born in England, Scotland and Wales in one week in March 1946 [8 (link), 13 (link), 24 (link)]. At the 24th follow-up, the target sample was 2816 study members still living in mainland Britain; this is the maximum sample used in the analyses. Of the remaining 2546 (47%) study members: 957 (18%) had already died, 620 (12%) had previously withdrawn permanently, 574 (11%) lived abroad, and 395 (7%) had remained untraceable for more than 5 years.
The postal questionnaire was sent out when study members were age 68; up to two reminder letters were sent to those who did not return a completed questionnaire. The home visit by a research nurse including blood sample collection took place at age 69 for the majority (97%), and at 70 years for the remainder. A short questionnaire, covering questions the research nurse asked at the home visit was posted to study members who did not wish to have a nurse visit. For this data collection, we obtained ethical approval from the NRES Queen Square REC (14/LO/1073) and Scotland A REC (14/SS/1009). This also included a protocol for collecting data on behalf of those who no longer had capacity to give consent (supplementary information).
The postal questionnaire was sent out when study members were age 68; up to two reminder letters were sent to those who did not return a completed questionnaire. The home visit by a research nurse including blood sample collection took place at age 69 for the majority (97%), and at 70 years for the remainder. A short questionnaire, covering questions the research nurse asked at the home visit was posted to study members who did not wish to have a nurse visit. For this data collection, we obtained ethical approval from the NRES Queen Square REC (14/LO/1073) and Scotland A REC (14/SS/1009). This also included a protocol for collecting data on behalf of those who no longer had capacity to give consent (supplementary information).