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My father is in the National Survey of Health & Development study of people born in Britain in March 1946, "the longest continually running major birth cohort study in the world": https://en.wikipedia.org/wiki/National_Survey_of_Health_%26_...

He seems to enjoy it, especially as a retired research psychologist. Every few years he goes to London and they run tests, see how long he can stand on one leg, do various scans etc. They are currently running a sleep study using wearables.

The study also had a 70th birthday party in 2016 for the cohort, which I got to go to as a guest. Apparently very few people have dropped out, so hopefully it's a positive experience for most people.

There's also a book about the study: https://www.amazon.co.uk/Life-Project-Extraordinary-Story-Or...

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