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The Epidemiological Paradox

Author: Ruoxi Lin

Editors: Shirley Chen and Kevy Chen

Artist: Jenny Luo

In the field of epidemiology, the mental and physical health status of different racial groups living in the United States often varies based on three main factors; socioeconomics, genetics, and racism. It’s also been established that low socioeconomic status is almost always associated with poorer health and higher mortality rates in a population. Despite this, a recurring discovery that arose from different studies has perplexed epidemiologists since the late 1900s, culminating in a CDC report showing that Hispanic individuals– a group with lower than average income, insufficient healthcare and education, and poverty rates more than twice that of non-hispanic whites’– had a lower risk of mortality from any cause compared to other racial groups.

The first report of this phenomenon was done by Kyriakos Markides in 1986. At the time, Markides’ ideas were met with skepticism and criticism by his peers due to the contrary nature of his findings. However, as more attention was brought to his studies and immigrant healthcare policies, more scientists began to note a distinct discrepancy between the health of non-Hispanic whites and Hispanics. How could a group that not only historically lacked sufficient healthcare, but also had higher rates of obesity, cardiovascular disease, and type 2 diabetes compared to non-Hispanic whites, have a longer lifespan than their better-off non-Hispanic white counterparts? Over the years, researchers have created multiple hypotheses and claims to explain this paradox, such as the Barrio advantage, acculturation, and the salmon bias. 

The Barrio Advantage is a theory originating from a 2004 study of health advantages in ethnically high-density homozygous neighborhoods; due to increased social support and strength in a community, ethnic groups living in the same neighborhood may harbor significant advantages for their health. Based on this theory, Hispanics living in ethnic communities with a large proportion of their group may exhibit signs of better health overall due to having extended social network support systems. Even while living under poor economic conditions, they may be able to establish not only strong family kinship– an already vital part of Hispanic culture– but also mutual relations in the community. Social connectedness promotes healthier decisions and mental wellness among individuals in a population. While the Barrio Advantage is plausible and has occurred in other populations, the extent to which it may help ethnic groups out under different living pressures could be questioned.

Acculturation refers to social, cultural, and psychological assimilation to a different, often dominant culture– a process most immigrants go through to varying extents. This hypothesis argues that through closer contact with American culture, Hispanics lose their positive traditional health practices in favor of adjusting to American practices, impacting their health negatively. An example of this would be breastfeeding; breastfeeding is a behavior that’s been shown to protect infants from inflammation, ear infections, and possibly even Sudden Infant Death Syndrome– while also providing the mother with protection from certain cancers and various health benefits such as bone strength. In a 2004 study that examined the proportion of Hispanics who breastfed their children compared to other ethnic groups’ proportions, it was discovered that Hispanics were far more likely to breastfeed than white mothers, with this frequency decreasing after each subsequent generation. This survey was done alongside another that controlled for acculturation, based on questions about attachment to traditional values and ethnic groups. Based on the findings, it’s possible that lack of acculturation could have played a part in the Hispanic paradox– though the effectiveness of controlling for acculturation in a study should be considered.  

The salmon bias hypothesizes that older adult migrants will return to their home country when expected to die shortly, which could lead to “ statistically immortal” subjects whose deaths may not have been recorded in the statistics of their home country. Multiple studies have hinted at support of this in the past with significant rates of return migration from the United States, as it fits in with Latino culture’s familism emphasis. However,  a 1999 study from the American Journal of Public Health refutes this bias with a claim stating that U.S.-born immigrant Latinos who weren’t affected by migration factors still had superior health compared to U.S.-born non-Latino whites, and therefore, the salmon bias couldn’t be used to explain the paradox entirely. Another study utilizing social security number data affirms the belief of a potential salmon bias but claims that the bias itself was too small to explain the paradox as a whole.

Just as epidemiology is broad, the various hypotheses developed to explain this occurrence are diverse. Unfortunately, there is still a great need for research on minority groups such as Hispanics, and a lack of statistics based on migrants in the past. Recent milestones include the 2019-2021 CDC report that affirmed low mortality rates for Hispanics based on the ten leading causes of death in the U.S., and a paper published in 2020 noting that the paradox could apply on a global scale for Hispanics living in countries such as Columbia and Cuba, future analyses and investigation may finally uncover the secret behind this epidemiological paradox. 



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