LOMA LINDA, Calif. – Like it or not, health disparities -- differences in health index between groups of people -- exist in our society. These differences can affect how frequently a disease affects a group or how often the disease causes death.
Individuals of distinct racial/ethnic background may also show disparities in their health, on average. For example, studies have shown that, in terms of chronic disease incidence, Blacks have a higher risk of hypertension, stroke and renal failure compared to Whites. The reason for this disparity is still unclear but may be due to increased prevalence of disease risk factors among Blacks, and perhaps differences in lifestyle and socioeconomic status.
Inflammation is a common causal pathway for a number of cronic diseases and is strongly influenced by sociodemographic factors and lifestyle. Yet, less is known about factors that may influence the inflammatory response in people with different race/ethnic backgrounds.
This prompted scientists at the Loma Linda University's School of Public Health to conduct research on the relationship between ethnicity and blood levels of inflammatory markers. This study was a cross-sectional analysis of the data gathered from the Adventist Religion and Health Study (also known as Biopsychosocial Religion and Health Study/BRHS), a substudy of the Adventist Health Study-2 (AHS-2).
Approximately 20,000 participants randomly selected from the nearly 100,000 AHS-2 cohort were sent a 20-page religion and health questionnaire, and about 11,000 returned the questionnaire. The data collection began in September 2006 and was largely completed by August 2007. The study population consisted mainly of Black and White Seventh-day Adventist males and females who were aged 35 and over. In addition to completing the questionnaire, 508 Religion Study participants also attended study-specific clinics in Southern California (Loma Linda, Riverside and Los Angeles) to be assessed for several biologic indicators and anthropometric measurements.
The results of this study, as published in Ethnicity and Disease, Volume 21/Spring 2011, were interesting. "We found that Blacks showed higher level of inflammation than Whites, based on IL-6 levels, which may be an important marker in explaining health disparities among Blacks and Whites. In addition, the vegetarian diet and increased exercise were associated with reduced inflammation levels, and may therefore be protective against inflammatory-related health problems," says lead author Michael Paalani, DrPH.
Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) are cytokines used by researchers to detect inflammation along with C-reactive protein (CRP). They are associated with a pro-inflammatory response while interleukin-10 (IL-10), another biomarker, has anti-inflammatory effects. These markers were assessed from fasting blood samples provided by participants on the day they attended the clinic.
"This study has shown that IL-6 may serve as an important ethnic-specific cytokine that is higher among Blacks than Whites, while the other pro-inflammatory (TNF-α and CRP) and anti-inflammatory (IL-10) markers did not differ between Blacks and Whites," says Jerry Lee, PhD, principal investigator of ARHS.
"As far as the ethnic differences in TNF-α are concerned, the results are mixed -- a study in United Kingdom found that TNF-α levels were higher among Blacks in relation the Whites, while another study in the U.S. found no significant difference in TNF-α levels among Blacks and Whites. Therefore, geographic location, environmental factors, and other variables such as diet, exercise and body mass index may play an important role in the onset of inflammation among different ethnic groups," adds Dr. Lee, who is also professor of health promotion at the School of Public Health, Loma Linda University.
Healthy diet and exercise do have some part in decreasing inflammation levels. This study, for instance, found that engaging in exercise and consuming a vegetarian diet was associated with lower inflammation levels. Vegetarians demonstrated a lower blood concentration of CRP compared to non-vegetarians consistent with previous research showing that long-term vegetarians have lower risk of coronary heart disease and an improved antioxidant and inflammatory status compared to non-vegetarians.
The results were also similar with those of previous studies in showing that greater amounts of regular physical activity have been associated with elevated IL-10 levels in healthy older males, and aerobic exercise training has been reported to exert anti-inflammatory effects in type-2 diabetics due to increases in IL-10 concentrations.
"This study may help to show that ethnic differences in inflammatory health risk may be present among other populations, and should be further investigated. Moreover, healthy lifestyle changes, including the incorporation of a vegetarian diet and increased exercise may provide beneficial health effects," concludes Dr. Paalani.
Adventist Health Study-2 (AHS-2) is one of the largest and most exciting health studies of its kind ever designed and will have national importance and international significance. It is a cohort study of over 96,000 Seventh-day Adventists in the U.S. and Canada who enrolled between 2002 and 2007. Adventists, due in part to their unique dietary habits, have a lower risk than other Americans of heart disease, several cancers, and probably high blood pressure, arthritis, and diabetes. This, along with their wide variety of dietary habits, provides a special opportunity for careful research to answer a host of scientific questions about how diet (and other health habits) may change the risk of suffering from many chronic diseases.
Two previous studies on Adventist health involving 24,000 and 34,000 Californian Adventists have been directed from Loma Linda University over the last 40 years. These have been among the first to raise scientific awareness of the close relationship between diet and health. This groundbreaking work has brought visibility and accolades to the lifestyle recommended by Seventh-day Adventists from both the scientific and lay communities. AHS-2 is conducted by researchers at Loma Linda University School of Public Health. For more information, visit www.adventisthealthstudy.