Research suggests your social status could affect your health

Photo credit: NPR

Photo credit: NPR

By Emma Gruner, Staff Writer

In today’s modern world, biology and sociology are often considered separate disciplines. The former governs the basic functionality of living creatures, while the latter governs the more complex, nuanced world of human interaction. Yet as one recent study shows, the two fields can intersect in surprising ways. A collaborative research team from Duke University, Emory University, and the University of Montreal recently concluded that, based on observations of rhesus macaque monkeys, an individual’s social status has a direct biological link to the strength of their immune system. The team published their findings in Science on November 24.

Researchers are aware of the existence of a connection between social status and health in humans. On average, American individuals in the higher socioeconomic classes live 10-15 years longer than those in lower classes. However, the exact nature of the connection has never been determined. Does low status cause poor health, or does poor health cause low status? Most evidence points to the former; poverty-ridden individuals are more exposed to toxic substances, have less access to high-quality food and shelter, and are more likely to engage in risky behavior. Yet many have often wondered whether, in some instances, poor health itself is capable of driving one to homelessness.

To explore this idea, a team of researchers decided to turn to the rhesus macaque monkey, whose strictly hierarchical societies are somewhat analogous to those of humans. This “class system” could be seen through the monkeys’ behaviors; higher-ranking monkeys were more likely to spend time grooming each other, while lower-ranking monkeys were more susceptible to harassment or social isolation. The researchers manipulated this hierarchy by organizing 45 captive female macaques into new social groups in which none of them knew each other. The macaques introduced into their societies first were inclined to assume the dominant status, while the subsequent additions assumed ever-lower rankings.

After three months, the researchers took blood samples from the macaques in order to measure gene expression in various types of immune cells. Their findings revealed several significant trends.  For example, the high-ranking monkeys generally produced more cells to fight viruses, such as the aptly named natural killer cells. In contrast, the low-ranking monkeys displayed heightened gene activity in cells responsive to bacterial infections. However, in both cases, the low-ranking monkeys were at a disadvantage. The lower number of natural killer cells left them less prepared to fend off viral infections, while their heightened inflammatory response in reaction to bacteria put them at higher risk for tissue damage and disease.

Interestingly enough, though, these effects were not irreversible. After the initial study, the scientists reorganized the macaques, changing their relative social statuses in the process. Three months later, they reevaluated their immune system activity and found that once again, the highest-ranking monkeys were the most adept at fighting infections, regardless of what social status they had held previously. Of course, there could be other variables at play. Michael Kobor of the University of British Columbia points out that the study did not account for the monkeys’ early life history, which can have long-lasting effects on overall health. Also, subtle genetic differences among the monkeys may leave some individuals better equipped to fight illness. Nonetheless, a strong correlation has been established; even Kobor asserts that the study was “super well done”.

The implications of these findings, particularly as they pertain to humans, are either troubling or fascinating, depending on one’s perspective. On one hand, it suggests that social reform movements like universal health care or sanitation initiatives can only go so far; supposedly, as long as class differences exist in our society, the lowest social groups will continue to be disadvantaged from a health standpoint. Yet others take a more optimistic approach. Study co-author Noah Snyder-Mackler of Duke says that “I like to think there is a positive societal message. If you take an individual out of their poor social environment, at least in these adults, you’re able to reverse the effects on their immune cell function.” Mackler’s colleague Jenny Tung, also of Duke, echoes this sentiment: “We’ve convincingly shown that chronic social stress by itself can change the way our body works. But the hopeful message is how responsive [immune] systems are to changes in the social environment. That’s really different than the possibility that your social history stays with you your entire life.” In any case, this study proves that even nuanced social constructs have the potential to alter biological function, a finding that can be both frightening and exciting.

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