Wednesday, June 6, 2012

The Link Between Socioeconomic Status and Cancer

In class we’ve discussed many aspects of cancer. Some of these had to do with the most prevalent types of cancer in the United States, the survival rates, treatments, cancer risks, and many other related topics. There is one possible related risk factor which we did not discuss: socioeconomic status of the patient. In an article titled, Impact of Socioeconomic Status on cancer incidence and stage at diagnosis, scientists explore the relationship between socioeconomic status and cancer incidence. Combining data from the Surveillance, Epidemiology, and End Results (SEER) Program at the National Cancer Institute, a population-based cancer registry, and the US representative National Longitudinal Mortality Study (NLMS), which provides self-reported demographic and socioeconomic data, researchers were able to examine the connection between the two.

Socioeconomic status is still very prevalent in cancer incidence, despite all of the advances in identifying risk factors and treatment for the disease. In fact, since so many disadvantaged groups were suffering from cancer at a larger rate, Congressional legislation was prompted and the NIH (National Institutes of Health) Center for Minority Health and Health Disparities was established. The NLMS data had to be used with that of the SEER Program because individual socioeconomic status (SES) – for example, education, occupation, and income – are not obtained by SEER. They have had to rely more on aggregate ecological data. This study used the record linkages to assess cancer incidence, tumor characteristics, and patient survival, based on race/ethnicity, immigrant status, health status, and health care access (availability of health insurance).

The study begins with researchers matching SEER cancer patient records to NLMS records for patients diagnosed between 1973 and 2001. The SEER registries included the states of Connecticut, Hawaii, Iowa, Kentucky, Louisiana, and Utah; the areas of Detroit, Los Angeles, Northern California (the greater bay area), and Seattle; and greater California (excludes L.A. and Northern California). They used an algorithm to match the reports using social security numbers, names, and birth dates. In total, they compared 2.4 million NLMS records with 4,172,139 patient records in SEER registries, for a total of 26,844 patient matches. Of these, 2,663 patients were diagnosed with more than one primary cancer, resulting in a total of 29,883 primary cancers diagnosed. Some patients had to be excluded because of various problems with follow-up information, residency, or diagnoses too late for follow-ups.

All of the demographic and socioeconomic variables used are from self-reports, except age, stage, and sex at diagnosis. There were five categories of educational level used: less than high school, high school graduate, some post high school education, college education or beyond, and unknown. Employment status was classified into five categories: employed, unemployed, retired, unable to work, and outside the labor force. Both of these classifications are shown in the tables.

Incidence analyses were performed for all cancers combined and for six major cancers separately: colon/rectum, breast, lung, uterine cervix, prostate, and melanoma. Age specific cancer incidence rates were calculated and adjusted using the age composition of the 2000 US standard population. Only the first primary cancer diagnosed in a patient was counted, regardless of cancer site, and follow-up time was allowed to accumulate only until the date of diagnosis of the first cancer.
Table 1
The tables show specific cancer incidence with relation to the socioeconomic factors I’ve described above. Table 1 above shows the data for all cancers combined to show how the total cancer incidence burden varies by socioeconomic characteristics. There were many correlations between various factors and specific cancer incidence. For example, as shown in Table 2 below, men with a less than high school education and those with a high school education had lung cancer rate ratios of 3.01 and 2.32, compared to those who were college-educated. In Table 3 below, compared with the college-educated, men and women with less than a high school education had ratios of 0.79 and 0.74 for prostate and breast cancer incidence.
Table 2

Table 3
Income gradients in male and female lung cancer incidence were significant as well, with those with incomes less than $12,500 having a greater incidence rate than those with incomes above $50,000. However, what’s interesting is that men with lower incomes were at reduced risk when compared to those with an income greater than $50,000.

Overall, Hispanics and Asian/Pacific Islanders had significantly lower incidence rates for all cancers, when compared with non-Hispanic whites (Tables 2, 3, 4). When comparing non-Hispanic whites with non-Hispanic blacks, those who were black had a higher overall cancer rate, with specifically higher rates of lung and prostate cancer.

For the first time, these researchers have demonstrated disparities in cancer incidence and socioeconomic status for a large portion of the United States. The racial and ethnic patterns in cancer incidence found in this study are consistent with those obtained from other data. Interestingly, there was a significantly lower rate of cancer incidence in those who were Asian/Pacific Islander or Mexican when compared with those who were non-Hispanic blacks and in lower education and income brackets.

Some of the social inequalities in cancer incidence may be related to other socioeconomic and demographic differences in risk factors – for example, cigarette smoking, poor diet, physical inactivity, obesity, or sun exposure. Also, disparities in health care access and availability (like cancer screening) may contribute to differences in cancer deaths. Those who have a lower socioeconomic status are more likely to smoke or be obese. However, these may not always be an accurate sign of cancer incidence because some risk factors, or other things which affect socioeconomic status, can be encountered over a period of time (like educational level) which can’t be directly contributed to a certain area.

I think that this examination into the relationship between socioeconomic status and cancer incidence only further seconds the hypotheses that have been made regarding health care in the United States. Usually, those who are less fortunate and are in the lower income bracket tend to have more health risks, either because they don’t have access to preventative care or are just more likely to engage in risky behavior. I do think it’s strange, however, the study mentions that when examining those who reside in the SF Bay area, breast and prostate cancer have larger incidence when socioeconomic status increased. Following my past comment and the general findings of the study, one would think that they would be lower. This leads me to believe that something else is playing a role in the incidence of breast and prostate cancer, something which is closely related to those with a higher socioeconomic status. This sector of the population must be more likely to engage in certain risk factors which lead to these incidences. What this could be is unknown, but it could be contributed to the food they eat (maybe these people are more likely to eat fast food because of busier schedules) or even general stress they may endure.

I’m curious as to how the government will go about developing new policies to combat this growing disparity between socioeconomic status and cancer incidence. Will these findings mean anything to policymakers? It’s important to note that these findings can also be applied to the rest of the health care world. More often than not, those with a lower socioeconomic status are more likely to suffer from detrimental health problems because of their decreased access to health care and, perhaps more importantly, preventative health care.

If you’d like more details on the specifics of the statistics used in this study, or to view all of the tables of individual cancer risks, you can access the article here: