Heard that colonoscopies don’t prevent colorectal cancer deaths? It’s complicated.

In the recent study that made headlines, researchers randomly assigned 84,585 people in Poland, Norway, and Sweden to a group that was offered colonoscopies or to a group that received usual health care.

After 10 years, the colonoscopy group had an 18 percent lower risk of colorectal cancer but no lower risk of dying of the disease. However, only 42 percent of people in the colonoscopy group chose to have the procedure. Among those who did, the risk of colorectal cancer was 31 percent lower—and the risk of dying was 50 percent lower—than in the usual-care group.