Infant Hair Cortisol: Associations with Multidimensional Socioeconomic Status

• In Event: 3-168 - Untangling the Complex Relations Between Early-life Adversity and Stress: Insights From Physiology and Longitudinal Modeling

Integrative Statement

Background: Young children of low socioeconomic status (SES) are more likely to have dysregulated cortisol (Blair et al., 2013), which is a key physiological mechanism through which early life stress leads to adverse health outcomes (McEwen, 2006). Many adult biomarkers of allostatic load, the wear and tear on the body of chronic physiological stress (e.g. cholesterol or insulin resistance), are not sensitive markers during infancy because effects on these systems take years to accumulate. Thus, it is crucial to identify infant biomarkers sensitive to chronic physiological stress. Hair cortisol indexes cumulative cortisol exposure over time, and thus may serve as a risk marker of adverse long-term health outcomes, but its sensitivity to socioeconomic stress during infancy has not been well established. As both SES and cortisol are multidimensional, nuanced consideration of these associations is critical to elucidate mechanisms underlying socioeconomic health disparities.

Methods: We examined multiple socioeconomic indicators in relation to hair cortisol and diurnal salivary cortisol in 12-month-old infants (N=90, 42% Caucasian). Measures of parent education, household income-to-needs ratio, parent occupational prestige, neighborhood chaos, household chaos, and household food insecurity were derived from parent report. Infants and parents provided hair samples which were assayed to yield hair cortisol concentration, an index of chronic physiological stress. Infant salivary cortisol was sampled at waking, afternoon, and bedtime across three days, yielding salivary cortisol area under the curve (AUC) as an index of diurnal physiological stress.

Results: Infant hair cortisol was positively correlated with parent hair cortisol (r = .42, p < .01). Higher infant hair cortisol was associated with lower income-to-needs ratio and parental occupational prestige and higher food insecurity, household chaos, and neighborhood chaos (see Table 1). Stepwise linear regression indicated that parent hair cortisol, food insecurity and neighborhood chaos all uniquely contributed to infant hair cortisol, accounting for 38% of the variance, F (3,68) = 13.32, p < .001. Income-to-needs ratio and parent education, which are more widely used SES indicators, did not account for additional variance and were excluded from the final model. Infant salivary cortisol AUC correlated positively with food insecurity and household chaos (Table 1).

Discussion: Results suggest that in early childhood, hair cortisol relates to multiple dimensions of SES and may be more sensitive than salivary cortisol to the cumulative effects of poverty. The specific associations of food insecurity and neighborhood chaos with infant cortisol parallel adult research linking hair cortisol to unpredictable and unsafe contexts (e.g. Henley et al., 2014). Food insecurity and neighborhood chaos both contributed to infant hair cortisol above and beyond parent hair cortisol. Future research should explore potential mechanisms that may underlie these associations, such as parenting quality and the predictability and structure of the infant’s day-to-day experiences. Findings underscore the need for multidimensional assessments of SES when examining physiological impacts of poverty, and support the use of hair cortisol as a sensitive biomarker of SES-linked adversity in early childhood.

Authors

• Amanda Tarullo, Boston University
  Presenting Author

• Charu Tara Tuladhar, Boston University
  Non-Presenting Author

• Jerrold S. Meyer, University of Massachusetts Amherst
  Non-Presenting Author