Context Matters: Preliminary Evidence for Differential Associations Between Observations of Positive Affect in Social vs. Non-social Contexts with Adiposity Across Infancy

Excess adiposity during the first year of life places children at increased risk f or adverse health outcomes across the lifespan. Previous studies have suggested that a temperament high in negative affect during infancy is associated with higher adiposity, yet few studies have examined whether positive affect shows similar associations. The current study examined cross-sectional and longitudinal relationships with an across early and late infancy between three measures of adiposity and positive affect, by observing positive affect in both a social and a non-social context. Data were available on 125 infants at four months of age, and again at 12 months of age for 79 of these infants. Our analyses did not find any cross-sectional associations between positive affect and adiposity (all P>.05). However, in the longitudinal analyses, positive affect in a non-social context, when observed at four months of age, was positively associated with higher z scores for weight-for-length (zWFL; ß = 1.56, SE=0.68, P=.03) and body mass index (zBMI; ß = 1.20, SE=0.64, P=.06) at 12 months of age, while positive affect observed at four months of age in a social context was associated with a lower percentage of body fat at 12 months of age (ß = 11.45, SE=4.88, P=.02). These findings provide preliminary evidence that levels of positive affect associate with adiposity in infancy, but suggest that the direction of association may be specific to the context.