Can a DNA test tell you how long you'll live?

What the studies say

Twin studies put the inherited share of lifespan at about 20 to 30 percent. They compare identical and non-identical twins to separate the effect of genes from the effect of environment.

Later studies of very large family trees found a lower inherited share. They showed that couples tend to have similar lifespans, although they are not blood relatives. Shared habits and surroundings had inflated the older figures.

Estimates still depend on the method. A recent analysis left out deaths from accidents and infections and found a higher inherited share. Every estimate leaves a large part to how you live, where you live and chance.

Why a longevity score misleads

A polygenic score adds up the small effects of many common variants into one number. It describes an average across a large group of people. Two people with the same score can live decades apart.

Most of these scores were built mainly from people of European ancestry. For everyone else they work less well, and can overstate or understate risk.

APOE is the best-known single gene. Its e4 form raises the chance of Alzheimer's disease and some other age-related conditions. Many people who carry e4 live long, healthy lives.

A score or a variant changes your odds. It does not decide the outcome.

What your DNA can tell you

Your DNA can show how you process certain medicines and which health checks may be worth starting earlier. It can also show conditions you could pass on to a child, and how you handle some nutrients.

A whole-genome report lists the results that apply to you, each with its next step. A scientist checks every result before it goes in the report.

Informational and educational, not a diagnosis. Bring anything of medical consequence to your physician.