Women with Alzheimer’s disease tend to live longer than men with the disease — and a new study suggests that a gene on the X chromosome may help explain why.

Each person typically has one pair of sex chromosomes in each cell of their body. People assigned female at birth typically have two X chromosomes, while people assigned male at birth typically have one X chromosome and one Y chromosome.

Researchers say a gene called KDM6A may explain why women with Alzheimer’s disease tend to live longer than men with the same condition.