Scientists say it all depend on caffeine habits, lifestyle and one factor we have no control over: our genes.
Related stories
The Deadlifting Grandma: 'I'm a world champion'
'My mother apologised': A survivor's journey after genital mutilation
Cancer patient told she will get drug which could make her life longer
New hope for breast cancer patients as life-extending drug now on NHS in England
Here's why an Arizona medical examiner is working to track heat-related deaths
Chipotle Enlists Palantir on Food Safety Risks After Salmonella Outbreak