Epidemiological risk factors for a disease could give significant clues as to the etiology, or cause, of a disease.
The etiology of human breast cancer remains largely unknown. Risk factors associated with the disease could be classified into three extensive determinants: family history factors, hormonal and reproductive factors, and environmental factors. A current epidemiologic analysis concluded that 73% of breast cancers are attributable to environmental factors. Over 78% of cases happen in postmenopausal women. Late onset is consistent with the long latency periods usually related with chemical carcinogenesis in humans.
Studies of migrant populations and geographic variations in incidence of breast cancer recommend that lifestyle and environmental effects are involved in the etiology of the disease. Its rates in Asian and Mediterranean countries are considerably lower than in North America, yet, in some generations, its rate in female offspring of Asian immigrants to the United States approaches the American rate.
Current studies point out that its rate in Japan is increasing, coincident with the westernization of the Japanese lifestyle. In general, the incidence of breast cancer in American Indian and Alaskan Native women has been lower than in most of the other racial/ethnic groups in the United States. Migration of these Native American families has caused an upsurge in the rates.
An elevated occurrence of breast cancer has been noted in the U.S. northeast, particularly the New York-New Jersey-Pennsylvania area, which is amongst the most heavily polluted areas on the continent in terms of industrial and vehicular emissions. An increased risk of breast cancer was reported for postmenopausal women as well who lived for more than 10 years near an industrial facility in Long Island, New York.
While the association of numerous risk factors, like family history and reproductive patterns, with breast cancer has been well established for several years, work in the past 10-15 years has added considerably to our comprehension of disease etiology too.