Developmental and Temporal Approaches to Human Biology and Health in Samoa

Sunday, 16 February 2014
Crystal Ballroom A (Hyatt Regency Chicago)
Stephen McGarvey , Brown University, Providence, RI

The impact of global socio-economic forces on current population biology and health among Samoans has produced very high body mass index (BMI), adiposity and cardiometabolic risk  levels over time. These are associated with individual and ecological measures of modernization. In particular, obesity, type 2 diabetes, hypertension and lipid and lipoprotein risk levels are at extremely high levels throughout the Samoan archipelago, and among Samoans and other Polynesians in the US and other high income nations to which they emigrated in the last 40 years.

The presentation will emphasize the integration of evolutionary, demographic and historical forces with contemporary nutritional exposures, genetic and epigenetic influences, culturally patterned behaviors, and world economic forces as a way to understand the high levels of non-communicable disease in Samoans. This approach may also allow for efficacious and sustainable interventions. 

Globally obesity is rising rapidly with each generation more overweight than the last, suggesting that the Samoan pattern of obesity, once remarkable and uncommon, may become more common. Thus, this relatively isolated and rapidly modernizing population can stand as an excellent model for environmental and genetic forces driving global obesity and non-communicable disease risk trends. Earlier results documented the rise in NCD risk factors with economic development and individual dietary intake and physical activity pattern across sex and age groups. Recent work showed how global and Pacific political-economic forces influence food availabilities and prices.

The unique population history of the Samoas has led to evolutionary scenarios about the forces of genetic drift and natural selection on key reproductive success traits related to energy storage, availability and metabolic use. This led us to search for the biologically-based susceptibilities underlying the body fatness and NCD risk factors. We identified familial aggregation and associations with genetic variation for NCD traits and also found gene-by-environment interactions. We do not have any solid evidence for any special unique genetic variants that predispose Samoans to obesity.

Two new research directions may also contribute interdisciplinary answers to questions about NCDs in Samoans, We are conducting genome-wide association studies (GWAS) of with quality dietary and physical activity data. New studies on maternal, pregnancy and early life factors on child health are also underway, including establishing a Samoan birth cohort focused on fetal growth rates in relation to maternal factors and gestational exposures and  how fetal growth rate variations influence postnatal growth rates in this overweight population. This lifespan developmental approach emphasizing fetal and early life influences and adaptive mechanisms along with the broader temporal perspectives about changes in ways of life should will yield novel findings and interpretations about Samoan health and human biology.