[eftpotrm]

IIRC the major factor in that was found to be that left-handed people within the age ranges where significant numbers of them are dying of natural causes had usually been brought up to suppress left-handedness, so are reporting as right-handed and skewing the data.

[robertlagrant]

But why would that mean that the people who didn't suppress died so much younger?

[verteu]

> [A]ccording Chris McManus, the researchers made a "very subtle error"...

> Halpern and Coren took a list of the people who had recently died and contacted their families, asking whether or not their relative had been right- or left-handed.

> Looking at 2,000 cases, they saw that the average age at death of the left-handers was about nine years younger than of the right-handers.

> On that basis, they concluded that left-handers died earlier.

> At first glance, that seems persuasive. What did the researchers do wrong?

> "Their mistake was that they only looked at the dead," Chris McManus explains.

> The point is that left-handers are more common now than they used to be, so - at least at the time the research was published - left-handers were on average younger than right-handers.

https://www.bbc.com/news/magazine-23988352