More on the relationship between SES and Cancer

The influence of education was weak, but significantly positive in case of invasive breast cancer in women. This is consistent with findings revealed in other studies. Parity, age at first birth, and use of MHT, are all associated with both education and breast cancer, which probably explains the moderate attenuation of the positive link between education and breast cancer in the multivariate analyses. Unlike the findings in some other studies, the direct link between endometrial cancer and educational attainment was established and this association was not attenuated when adjustment was made for BMI and MHT in the multivariate analyses. It appears that the moderate overall positive relationship between occurrence of cancer and educational attainment is mainly driven by the positive associations for endometrial and breast malignancies.

Results derived from studies focusing on educational attainment and prostate cancer have been inconsistent. In this cohort, the association between education and prostate cancer was weakly positive and statistically significant only for localized disease. For localized and advanced prostate cancer, the point estimates were similar, but the power to establish a positive link with advance disease was restricted. The weak positive association in case of prostate cancer remained largely unaffected by the multivariate analyses. This is not surprising given the scarcity of strong risk factors for this particular malignancy.

In the cohort, the direct link between education attainment and melanoma of the skin was in line with findings of earlier studies. Typically, individuals with higher SES are more likely to take part in outdoor leisure activities and go on vacations to places having high sun exposure. All these factors may increase their overall melanoma risks.

Another significant aspect is that on an average, the AARP membership is likely to be more educated than the U.S. population taken as a whole. Nonetheless, the cohort comprises of a wide range of education levels, including more than 30,000 individuals, which is around 6.6% of the study population, having less than a high school education. The benefit of this wide range of education levels is that it allows researchers to reveal comparisons of the occurrence of cancer across different education categories.

Education helps identify several different aspects of the constructs ‘socioeconomic status’ and ‘social class’ and is used widely to indicate social ‘difference’ in epidemiologic studies. One specific advantage of investigating education is that it helps avoid reverse causation bias: occurrence of cancer may result in downward occupational mobility and lower income, but usually it will not affect educational levels achieved during early adulthood.

In summary, the NIH-AARP cohort data shows that significant education gradients pertaining to incident cancer risk exist in the U.S. Some of the malignancies are positively linked with educational attainment; and these positive relationships are largely of etiologic interest, considering that reducing educational attainment can hardly be used as a technique for preventing cancers of the prostate, endometrium, and breast or melanoma of the skin. However, most of the identified education-related associations are inverse, and these are apparent especially in case of smoking-related malignancies. Most likely, smoking accounts for some, but not all, of the increased risk of cancer among less educated men and women. Given that smoking is the mediating casual factor, decreasing the differential in smoking rates is a realistic strategy for taking care of SES-cancer inequalities. Similarly, given that smoking does not provide for inverse associations, more research is clearly required to identify the casual factors that influence the education-cancer gradients.

In the U.S. and several other countries, the prevailing education-cancer differences continue to be a cause for concern. However, they also provide an opportunity to obtain a better understanding of the etiology of cancer and eventually reduce its occurrence.