Beyond a catalogue of differences: A theoretical frame and good practice guidelines for researching sex/gender in human health

► Sex as a variable is an inadequate proxy for testing proposed biological mechanisms underlying male-female health differences. ► Sex and gender are entangled and health researchers should explore this entanglement. ► Fully understanding male-female health differences requires exploring social and biosocial mechanisms. ► Routine and automatic investigation of sex differences in health outcome is unwarranted and unscientific.