NU713 Unit 4 Fundamental Cause Paper, Colon Cancer Example

Level in 1990, Apart by 2022: A Fundamental Cause Reading of Colorectal Cancer Mortality in the Poorest and Least Poor Tracts of Composite Brennard County, Tested Against Pancreatic Cancer

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Purdue University Global

NU713: Epidemiology and Social Determinants of Population Health

Unit 4 Fundamental Cause Paper

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[Date]

Brennard County and its rates are composite; figures are bracketed placeholders for age-adjusted rates from state vital records.

The Pattern

Age-adjusted colorectal cancer mortality in Brennard County, calculated from state vital records for the poorest and least poor fifths of the county's census tracts, began at nearly the same level: about [25.1] deaths per 100,000 in the poorest fifth and [24.6] in the least poor fifth in [1990]. Over the next three decades both lines fell, but not together. The least poor fifth fell steadily, flattening after [2005] at a much lower level, and reached [11.2] per 100,000 in [2022]. The poorest fifth fell more slowly and reached [19.7]. A disparity that barely existed in 1990 had become a ratio of about [1.76] by 2022, or about [8.5] additional deaths per 100,000 residents each year in the poorest tracts. The question this paper asks is why the gap opened when it did.

Pancreatic cancer tells a different story. Over the same years, mortality stayed similar in the two groups and in [2022] stood at [11.9] per 100,000 in the poorest fifth and [12.3] in the least poor, essentially level.

The Theory

Link and Phelan (1995) proposed that socioeconomic status is a fundamental cause of disease, meaning that its association with health persists even when the diseases and risk factors that link them change. Later work set out four features of a fundamental cause (Phelan et al., 2010). First, it influences multiple disease outcomes. Second, it affects those outcomes through multiple risk factors. Third, it involves access to resources that can be used to avoid risks or to minimize the consequences of disease once it occurs. Fourth, the association is reproduced over time because, as old mechanisms are removed, new ones take their place.

The resources the theory names are money, knowledge, power, prestige and beneficial social connections. The theory's central claim is that people with more of these resources will use them to benefit from whatever protective knowledge and technology exist at a given time.

Applying the Four Features to Colorectal Cancer

Multiple outcomes. The same tracts that show a colorectal cancer gap also have higher mortality from heart disease, diabetes and several other cancers, as the county's earlier profile showed. Colorectal cancer is one outcome among many.

Multiple risk factors. The gap does not run through a single mechanism. Poorer residents are less likely to be screened, more likely to be diagnosed at a later stage, and less likely to complete treatment on schedule. Diet, physical activity and smoking contribute as well.

Flexible resources. This is where the theory explains the timing. Colorectal cancer screening, especially colonoscopy, spread widely from the late 1990s onward, and it can prevent cancer by removing polyps and find it early when treatment works best. Using that new technology requires resources the theory names. Money covers copays and deductibles. Knowledge helps a person understand why a test matters when they feel well. And some resources are very concrete in Brennard County: paid leave for the day of bowel preparation and the day of the procedure, and an adult who can drive a sedated patient home. A warehouse worker without paid sick leave, living alone, faces barriers that a salaried professional with a spouse does not.

The gap opened not because colorectal cancer became more dangerous for the poor, but because a way to prevent it arrived, and the resources to use it were unevenly shared.

Reproduction over time. In 1990, before widespread screening, there was little that money or knowledge could buy to prevent colorectal cancer death, so the rates were similar. When screening became the new mechanism, the resource advantage reappeared through it. If screening were to become universal and effortless, the theory predicts that another mechanism, such as access to newer treatments, would carry the gap forward.

Testing the Reading Against Pancreatic Cancer

The theory makes a prediction that can be tested. If resources matter because they let people use protective knowledge and technology, then diseases for which little can be done to prevent death should show smaller socioeconomic gaps. Phelan and colleagues tested this prediction in a national longitudinal mortality study and found that socioeconomic status was more strongly associated with mortality from highly preventable causes than from less preventable ones (Phelan et al., 2004).

Pancreatic cancer is a useful comparison because it has no effective screening test for the general population, is usually diagnosed late, and has poor survival regardless of resources. The county's data match the prediction: pancreatic cancer mortality is essentially level between the poorest and least poor tracts, while colorectal cancer mortality has diverged. This does not prove the theory for Brennard County, and other explanations, such as differences in smoking history, could contribute. But the contrast is what the theory would expect.

Limits of This Reading

The data are ecological. They describe tracts, not individuals, and the poorest fifth of tracts contains residents with many different circumstances. Tract poverty rankings may shift over three decades as neighborhoods change. Death certificates may misclassify cause of death, although colorectal and pancreatic cancer are usually recorded accurately. And rates for small populations are unstable from year to year, which is why the trend matters more than any single year.

Implications

If the theory is right, interventions that target one mechanism will narrow the gap only temporarily. A screening campaign may help, but the theory suggests two further strategies. The first is to reduce the resources needed to benefit from prevention: stool-based screening tests that can be completed at home remove the need for paid leave and a driver, and a health center that mails them to every eligible patient makes screening less dependent on knowledge and time. The second is to address the unequal distribution of resources themselves, through measures such as paid sick leave, which the state does not require. Phelan and colleagues argued that policies of this kind, which reduce inequality in resources or make the benefit of health knowledge automatic, are more likely to produce lasting reductions in disparities than interventions aimed at one risk factor (Phelan et al., 2010).

Conclusion

In Brennard County, colorectal cancer mortality diverged by neighborhood poverty after screening arrived, while pancreatic cancer mortality did not. The theory of fundamental causes explains both patterns and points toward interventions that reduce the resources needed to benefit from prevention.

References

Link, B. G., & Phelan, J. (1995). Social conditions as fundamental causes of disease. Journal of Health and Social Behavior, 35(Extra Issue), 80-94. https://doi.org/10.2307/2626958

Phelan, J. C., Link, B. G., Diez-Roux, A., Kawachi, I., & Levin, B. (2004). "Fundamental causes" of social inequalities in mortality: A test of the theory. Journal of Health and Social Behavior, 45(3), 265-285. https://doi.org/10.1177/002214650404500303

Phelan, J. C., Link, B. G., & Tehranifar, P. (2010). Social conditions as fundamental causes of health inequalities: Theory, evidence, and policy implications. Journal of Health and Social Behavior, 51(Suppl.), S28-S40. https://doi.org/10.1177/0022146510383498