标题：Fundamental Causes of Colorectal Cancer Mortality in the United States: Understanding the Importance of Socioeconomic Status in Creating Inequality in Mortality
摘要：Objectives. We used the fundamental cause hypothesis as a framework for understanding the creation of health disparities in colorectal cancer mortality in the United States from 1968 to 2005. Methods. We used negative binomial regression to analyze trends in county-level gender-, race-, and age-adjusted colorectal cancer mortality rates among individuals aged 35 years or older. Results. Prior to 1980, there was a stable gradient in colorectal cancer mortality, with people living in counties of higher socioeconomic status (SES) being at greater risk than people living in lower SES counties. Beginning in 1980, this gradient began to narrow and then reversed as people living in higher SES counties experienced greater reductions in colorectal cancer mortality than those in lower SES counties. Conclusions. Our findings support the fundamental cause hypothesis: once knowledge about prevention and treatment of colorectal cancer became available, social and economic resources became increasingly important in influencing mortality rates. Colorectal cancer is the third leading cause of cancer-related deaths among men and women in the United States. 1 In 2010 an estimated 142 570 people in the United States were diagnosed with colorectal cancer, and 50 370 people died as a result of the disease in the same year. 2 Over the past 30 years, there have been significant advances in the prevention of colorectal cancer, with reductions in mortality rates due predominantly to improvements in screening and early cancer detection. One of the primary goals of colorectal cancer screening is to reduce mortality by promoting early detection of the disease. Methods used to detect colorectal cancer also aid physicians in the identification and removal of adenomas, which can give rise to colorectal cancer. 3 However, because of the unequal distribution of social and economic resources in our society, knowledge about prevention and access to treatments for colorectal cancer is not universal but, rather, is unevenly distributed along the typical social cleavages of race, class, and gender. Thus, social inequalities in colorectal cancer outcomes remain remarkably evident even in an era of successful prevention and treatment strategies. 4 To gain a more thorough understanding of how existing social inequalities have slowed the decline in mortality attributable to colorectal cancer, we used the “fundamental cause” hypothesis to analyze almost 40 years of US death certificate data. This theoretical construct, first put forth by Link and Phelan, 5 stems from the observation that adverse social conditions are repeatedly associated with higher levels of mortality in distinctly different eras and settings. 5–9 According to the hypothesis, the association between socioeconomic status (SES) and mortality endures because access to resources such as knowledge, money, power, prestige, and beneficial social connections influences the extent to which people are able to avoid disease and death as well as harness protective factors that can be used to reduce morbidity and mortality. The fundamental cause hypothesis further predicts that as individuals learn how to better prevent or treat diseases, benefits stemming from these newfound abilities will not be distributed uniformly throughout a population. Instead, they will be realized to a greater extent by those who are less likely to face discrimination and stigma and are more likely to have access to socioeconomic resources such as education, money, and information, 7 thus resulting in health disparities along common social divisions such as SES and race. According to the hypothesis, more advantaged individuals, relative to their less advantaged counterparts, are poised to disproportionately gain from new health-enhancing capabilities, which may translate to earlier and more rapid reductions in mortality rates. We examined SES inequalities in colorectal cancer mortality in light of major advances in preventing or delaying death, advances predominantly due to improvements in screening and associated policy recommendations. Although colorectal cancer has been surgically treated for more than a century, an emphasis on the prevention of colorectal cancer through widespread screening has become routine only in the past 30 years. In July 1980, the American Cancer Society (ACS) first published recommendations for colorectal cancer screening. 10 In 1997, the US Multi-Society Task Force (MSTF), assembled by the US Agency for Health Care Policy Research in conjunction with the American Gastroenterological Association, published its first guidelines for screening for colorectal cancer. 11 The MSTF guidelines recommended that everyone with risk factors such as age (≥ 50 years), family or personal history of colorectal cancer, history of inflammatory bowel disease, chronic ulcerative colitis, adenomatous polyposis, juvenile polyposis, and hereditary nonpolyposis colorectal cancer be screened. Furthermore, following a positive screen, physicians should conduct a diagnostic evaluation of the colon and rectum, use recommended treatments (including the removal of adenomatous polyps), and consider follow-up surveillance after treatment. In 1997, influenced by MSTF’s recommendations, ACS revised its 1980 guidelines to include recommendations stratified by level of risk of developing colorectal cancer. 11 Since then, both ACS and MSTF have issued updates on a regular basis. 12 The 1997 ACS guidelines recommended that all individuals at an average level of risk begin colorectal cancer screening at the age of 50 years. Individuals at moderate risk, based on a personal or family diagnosis of gastrointestinal adenomatous polyps or colorectal cancer, were recommended to initiate screening at the time of onset, the age of 40 years, or 10 years before the youngest case in the family, whichever was earlier. High-risk individuals with hereditary predispositions to colorectal cancer or a personal diagnosis of inflammatory bowel disease were recommended to initiate screening at puberty, at the age of 21 years, or 8 to 15 years after the onset of inflammatory bowel disease, depending on their individual risk factors. 11 According to the fundamental cause hypothesis, developments in colorectal cancer screening, such as clearly stated, evidence-based guidelines and their widespread dissemination, will benefit people of high SES more than their low-SES counterparts, thereby creating new health disparities or exacerbating existing disparities over time. Specifically, we expected individuals living in high-SES locales to benefit from recent developments in colorectal cancer screening, beginning with the release of the first colorectal cancer screening recommendations by ACS. Furthermore, given that socioeconomic inequalities are reproduced and often accentuated over time, we expected the association between SES and colorectal cancer mortality to increase over time.
