Vikas Pandey, MD
Nordahl H,Osler M, Frederiksen B, Andersen I, Prescott E, Overvad K, et al. Combined Effects of Socioeconomic Position, Smoking, and Hypertension on Risk of Ischemic and Hemorrhagic Stroke. Stroke. 2014
“Rich people diseases” have stereotypically been defined as obesity, diabetes, hypertension, and gout, while “poor people diseases” have classically been diseases such as dysentery, malaria, and typhoid. This class struggle has always been a point of philosophical intrigue given the irony that poor people can avoid diseases of the poor by obtaining wealth, only to suffer from a different subset of medical illnesses that affect the wealthy. Education, another measure of socioeconomic status, has previously been linked to increased incidence of both ischemic and hemorrhagic strokes given the increased exposure to risk factors and inability to address these risk factors. Knowing which groups are most at risk for stroke is important from the public health standpoint given that specified intervention in these subgroups can potentially prevent the most cases.
The authors were testing the hypothesis that while there is a clear link to smoking and stroke risk, as well as hypertension and stroke risk, there is limited data on the interplay between socioeconomic position, smoking and hypertension and their combined effect on ischemic and hemorrhagic stroke incidence. The authors used a pooled cohort study with 68,643 participants from Denmark aged 30-70 and included information on socioeconomic position based on their highest attained education level. Qualitative smoking data and categorized hypertension data was also obtained. The authors analyzed this data using an additive hazards model that is used for assessing additive interactions in survival analyses. They found that smoking was clearly more frequent in those with low education and level of blood pressure was only slightly higher in the low education group. Out of 100,000 person years, low education was deemed to cause 181 extra cases of ischemic stroke in men and 93 extra cases in women. This difference was less marked in hemorrhagic stroke. The combined effect of exposure to all three risk factors was associated with 566 extra cases among men and 438 extra cases among women compared to no exposure. This result was more than what would be expected as a sum of their separate effects demonstrating a synergistic effect of the risk factors with one another.
The article demonstrated an additive effect between the three risk factors specifically studied as well as numerous synergistic links between subgroups of the risk factors. While some of the data may contain flaws such as underreporting (i.e. incorrect smoking reporting due to low education level) and confounding variables that are difficult to control for, the end message is still convincing in showing that legislation and public health campaigns may be more beneficial if aimed toward the lower socioeconomic classes as the same reductions in risk factors in both groups would reduce a larger number of cases in the lower socioeconomic class. Though the intention of this conclusion is well-guided, I feel that it is equally plausible that such a campaign toward the lower socioeconomic classes would have less of an impact. From personal experience in Miami-Dade county (approximately 20% living below the poverty line), stroke prevention measures do not seem to spur a change in health decisions for those of lower socioeconomic status as they do for aware and educated patients in a higher socioeconomic class. This aspect may be a little lost in the cohort studied from Denmark given the adjusted poverty rate is approximately 6% in the country, one of the lowest for any developed nation. For this reason, I feel future studies in evaluating the reception and comprehension of different stroke prevention policies as well as cultural differences in viewpoints toward personal health may further allow us to pinpoint more accurately the subgroup of patients for which our public health measures may be of the most benefit.