Infant Feeding Practice, Childhood Obesity, and Acanthosis Nigricans among American Samoan Children

Abstract

The global incidence of childhood overweight has been on a steady incline for decades and is affecting many developing countries, especially among Pacific Island nations (1). Children who are overweight or obese are likely to track as such into adulthood, increasing their likelihood of developing non-communicable diseases such as hypertension, heart disease, and type 2 diabetes (2). Childhood obesity has been shown to be associated with hyperinsulinemia, which is a marker for insulin resistance and risk for metabolic disorders and type 2 diabetes (3). Acanthosis Nigricans (AN) is a dermatologic condition characterized by the thickening and darkening of the skin, usually around the neck and armpits (4). Studies have indicated that AN is also associated with a hyperinsulinemia and may serve as a visual marker of it (5). Currently, a scarcity of studies that estimate the prevalence of overweight and obesity among American Samoa children 2 – 18 years old. Furthermore, the relationship between weight status, AN, early infant feeding practice (IFP), and early childhood growth is unstudied in this population.

These relationships have implications for further research, early prevention programs, and surveillance activity for obesity and AN. This dissertation examined the linkages among weight status, AN, early IFP, and early childhood growth among American Samoan children 2 – 18 years old. Chapter II reports on the estimated prevalence of childhood overweight and obesity among American Samoan children 2 to 18 years old and investigated the relationship between weight status and AN. In Chapter III, infant feeding practice (IFP) was introduced into the equation, assessing its effect on the relationship between weight status and AN among American Samoa Children’s Healthy Living (ASCHL) program participants. The analysis focused on whether or not infant feeding practice is a mediating factor for the relationship between weight status and AN. Finally, in Chapter IV, early childhood growth was added into the model to see if early infant growth mediates relationships between IFP and later childhood weight status, and IFP and manifestation of AN.

Results from Chapter II revealed that in 2013, 31.4% of children 2 to 18 years old were obese (OB). Furthermore, AN was present among 15% of the children. Presence of AN was positively associated with increasing weight status. Age was a modifying factor, as the prevalence of OB increased from 23.2% among 2 to 5 year olds, to 48.6% among 15 to 18 year olds. This pattern was also true for AN where the prevalence increased from 4.2% among 2 to 5 year olds, to 34.4% among 15 to 18 year olds. Chapter III showed that early IFP may be an important mediating factor in the relationship between weight status and AN, especially among OB children. When comparing prevalence of AN among healthy weight (HW) and OB children, those who were formula fed only were 5.05 (p = 0.0370) times more likely to have AN. Finally, in Chapter IV analysis showed that children who were formula fed exclusively for the first 12 months of life, grew faster and were more likely to have AN compared to those children that were either breastfed only or combination fed.

Although the direct cause of AN among insulin sensitive individuals is not entirely clear, it is believed to be linked to an insulin-like growth factor (IGF) that is probably elevated in individuals with hyperinsulinemia, leading to epidermal cell proliferation (4). These associations are important because AN may be used as a non-invasive way to identify children who are at an increased risk of developing diabetes (6). Exploring factors related to the presence of AN before its manifestation (such as in obesity without AN) is therefore important for hyperinsulinemia and insulin resistance prevention, and ultimately diabetes prevention in children.