1930s gangster George “Babyface” Nelson didn’t make it to old age, but other people who look younger than their years have a better chance than the rest of the population to do so (provided they avoid shootouts with the FBI).

People with youthful-looking faces tend to live longer, according to a Danish study published in the British Medical Journal. Scientists presented photos of 387 pairs of elderly twins to a group of nurses, trainee teachers and peers who were asked to guess the age of each twin.

The twins rated as younger looking tended to outlive their older-looking siblings — and not just because their big eyes, small chins and round faces garnered favor from others. There’s a biological explanation, the scientists say, related to key pieces of DNA called telomeres.

The younger-looking twins actually have longer telomeres, which indicate cells’ ability to replicate. Shorter telomeres are linked to faster aging and a number of diseases. In addition to DNA, stress may play a role, notes Professor Kaare Christensen of the University of Southern Denmark.

Over a seven-year follow-up study, the scientists determined that the bigger the perceived age difference between the twins in photographs, the more likely the older-looking twin would die first.

These findings emphasize the role that aging and appearance plays in medical evaluations. Doctors should be concerned when patients look significantly older than their years, says Professor Tim Spector, a U.K. expert on aging.

"Perceived age, which is widely used by clinicians as a general indication of a patient's health, is a robust biomarker of ageing that predicts survival among those aged over 70,” the researchers told the British Medical Journal.