Who gets endometriosis?
There are many popular misconceptions about the epidemiology of endometriosis and the factors that increase or decrease a woman's likelihood of developing the disease, which arise principally because studies have been poorly designed in the past. Thus, there is no evidence to support the commonly held belief that endometriosis occurs more commonly in middle-aged, upper class, ambitious, white women. This stereotype probably only demonstrates that such women have greater access to medical care and a laparoscopic diagnosis. Although the findings from the few appropriately designed studies have been inconsistent, some risk factors have emerged. Age is the major demographic risk factor: the risk rises with advancing age within the reproductive years, peaking among women aged 40-44 years. In many studies, the risk of endometriosis seems clearly related to an increased exposure to menstruation: thus, a short menstrual cycle length; long, heavy flow, and reduced parity have all been identified as risk factors. Factors which influence circulating oestrogen levels have been implicated: thus, the risk is increased for women with greater peripheral fat, and habits that lower oestrogen levels (e.g. smoking, exercise) seem to be protective. It has also been suggested that current use of the combined oral contraceptive is protective, although it is more likely that the pill simply masks the symptoms associated with the disease. Lastly, there is increasing evidence that endometriosis results from a complex interaction between genes that predispose women to develop the disease and environmental factors, such as exposure to pollutants. © 2005 Elsevier Ltd. All rights reserved.