India, Nov. 13 -- In India, speaking more than one language is rather commonplace. Many of us move between Hindi and English (and a jumble of the two) when we're outside, switch to our mother tongue at home, and adjust our words depending on who we talk to. Earlier, studies showed that speaking more than one language is associated with a lower risk of dementia. This constant mental juggling is now being linked to slowing the pace of aging itself.

A new study in Nature Aging looked at more than 86,000 people from 27 European countries and found that those who spoke only one language were about twice as likely to show signs of accelerated aging. Multilingual speakers were roughly half as likely. The more languages people spoke, the stronge...