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>The researchers lost touch with 13 people, while 57 people died and 332 declined to take part."

This is one of the major downsides to longitudinal studies— people are unpredictable.

I wonder if we'll see that change with the proliferation of communication across so many mediums. Between mail, email, texting, voice, social media, etc. staying in touch with a cohort might be much easier and more sustainable.

They lost touch with 2.6% of the participants. There is not much room for improvement there.

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