Man’s best friend may be helping pet owners remain healthy and live longer.

A study including 3.4 million Swedes, published in the journal Scientific Reports, indicates that people who live alone and are dog owners have a 33 percent lower risk of death than single people who are not pet owners.

People living with others also enjoyed health benefits from owning a dog, but to a lesser extent. Breed of dog also made a difference: Owners of terriers, retrievers, scent hounds, and other hunting breeds experienced the greatest protection.

The researchers did not determine why dogs may protect the health of their owners, but several possible factors include a strengthened immune system, better social well-being, and increased exercise from taking dogs on walks.

Having a dog as a companion also offers a form of emotional support, which may reduce levels of stress.