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Prof researches Samoan obesity epidemic

A U. epidemiologist is examining the problem’s origin and potential intervention strategies

By economic standards, the American territory in Samoa is relatively successful. But rapid modernization on this small Pacific island came at a price — two-thirds of adults are obese, the highest rate of any region in the world. Stephen McGarvey, professor of epidemiology and anthropology, has devoted much of his career to studying this epidemic and what it could foretell for other developing nations.

McGarvey got his start in the field “unintentionally,” he said. After finishing his master’s degree doing work in South America, he wanted to return to the high altitude Andes for his Ph.D. work. At the time, the “Sendero Luminoso,” or Shining Path, a Peruvian guerrilla group, was terrorizing villagers and the Peruvian military.

Because the group was particularly hostile to “outsiders,” McGarvey instead chose to study the Samoan population living on the Hawaiian island of Oahu, he said, adding that he was intrigued by the rumored “low-level obesity” there and its implications for modernization.

The research interest stuck. Since 1975, he has published dozens of studies on the Samoan population that cover everything from blood pressure and diet to stress management. McGarvey travels to Samoa at least once yearly, and up to three times in a year while collecting data.

Through decades of research, it became clear adult obesity in Samoa had reached epidemic levels. In the last month, McGarvey and his collaborators have published two studies ­on Samoan obesity — one examining the developmental origin of the obesity epidemic and one looking at a potential intervention strategy ­ ­— and they also have a forthcoming study on possible genetic causes.


Overweight at birth

Obesity begins early in life for American Samoans, according to study conducted by Nicky Hawley, a former postdoctoral fellow in McGarvey’s group, who came to his findings using the birth records of approximately 800 Samoan infants. The researchers found more than one in five infants qualified for a diagnosis of excessive birth weight. The newborns then showed “markedly” rapid weight gain. At 15 months of age, a full third of infants were overweight or obese.

To Hawley, the results illustrate that Samoans are not being reached at a critical age. “Childhood is too late,” she said.

Based on a model of infant growth, Hawley found a “window to intervene” before four months of age, she said. During that window, Samoan infants gained nearly 20 percent more weight than their counterparts in the United States, a change she said “really sets them up for obesity” later in life.

Consistent with other studies, the researchers found that formula feeding is associated with increased weight gain — but only in boys. While the researchers could not explain the gender difference, they believe the results could support exclusive breastfeeding as a “cost-effective and sustainable intervention” against Samoan obesity, the authors wrote in the study.

Hawley hopes to examine earlier development in a future study, using ultrasound technology to follow growth before birth, she said.


Forming healthy habits

During his time in Samoa, McGarvey forged connections with local health authorities. They told him they appreciated the work he and other researchers did to understand Samoan obesity but said they wanted him to investigate a possible solution as well, McGarvey said.  Lacking training in interventional research, McGarvey approached Judy DePue, a clinical professor of human behavior at The Miriam Hospital, to form a collaboration.

The result was Diabetes Care in American Samoa, the first major interventional trial to take place in American Samoa, DePue said. Many Samoans with diabetes know the basics of managing their disease but have trouble “putting it into daily and weekly practice,” McGarvey said. The trial was designed to address this by improving health literacy and establishing the habits that managing diabetes requires, he said.

The study was modeled after a previous trial, Project Sugar 2, that took a community health approach to managing diabetes among African Americans in Baltimore. DePue and her team worked to adapt the trial for the population in Samoa. Different villages were randomly assigned to receive only standard care or standard care with additional visits from community health workers, a model which she called the “gold standard” for trial design. The nurse-community health worker teams visited patients at their homes or workplaces to assess their conditions and discuss any of at least seven educational topics.

Staging an interventional trial on the island posed special challenges. The region is so impoverished that the researchers found even a $10 co-payment could deter people from seeking medical care, DePue said. The Samoans also required unique cultural accommodations. Patients preferred community health workers who came from their culture and spoke their language, for instance. Due to strong extended family ties, Samoans also expected trial workers to share supplies like blood sugar testing strips with them, but finite grant money left limited supplies to spare.

Cultural divide notwithstanding, the community intervention seemed to pay off, the study indicated. Over 42 percent of participants achieved significant reductions in blood measures of HbA1c, a proxy for average glucose levels, though they remained unhealthy by international standards. McGarvey cited the “tremendous formation of rapport” between the workers and patients as a reason for its success, pointing to data showing Samoans even became more comfortable talking to their doctors by the end of the year-long trial. McGarvey said he is working to have two medical students travel to Samoa to review medical records from after the trial’s completion. These students could examine whether the reductions in HbA1c levels are maintained or lost.

“It’s hard to change habits,” McGarvey said.


Genetic influences?

One question that remains for McGarvey is what genetic factors, if any, are at play in the extreme obesity in Samoans and other Polynesian populations. To answer this question, McGarvey and collaborators at the University of Pittsburgh and University of Cincinnati are carrying out a genome-wide association study on 3,122 Samoan adults.

To carry out such a study, the team obtained DNA from thousands of individuals and analyzed approximately one million genetic variations spread across the entire genome. They then correlated those variations to a trait — in this case, body mass index, a standardized measure incorporating height and body weight.

When the team did the analysis, a single genomic region on the fifth chromosome spiked above the natural baseline. McGarvey’s team is now pursuing detailed studies of that region to find the variation responsible, including adding measures like diet and other health variables to the analysis, he said. The project is currently in its fourth of five planned years.

While most of McGarvey’s work focuses on populations, the individual is still important to him, he said.

“One of my most memorable experiences is being thanked in 1981 by a woman whose high blood pressure I found in 1976 and referred for medical treatment,” McGarvey wrote in an email to The Herald. “I was moved deeply by her speaking openly and at length about what she had been able to experience in those five years, which she attributed to being alive and well due to her successful treatment for her hypertension.”


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