USA: An original article published in the Journal of Pediatrics evidenced the relationship between low family income with higher body mass index (BMI) and cortisol levels. In contrast, BMI and cortisol levels are unrelated to each other.
Cortisol is an indicator of hypothalamus-pituitary-adrenal (HPA) axis functioning. Poverty and low income, especially in early childhood, are stress-related, altering the HPA axis. Few studies are mentioning the effect of low income on cortisol outcomes.
The effects of glucocorticoids on development have genetic implications, and cortisol is a robust indicator of long-term impacts on development. Alterations to resting levels cause variations in genetic activity and alter brain functioning, which affects physical and mental health. Dr. Kim from Stony Brook University has previously concluded that "There is a positive association between poverty percentage and obesity." (CDC)
Considering this, Dr Batson from the Department Of Pediatrics and Center For Pediatric Obesity Medicine from the University Of Minnesota Medical School, with a team of researchers, conducted a prospective study to evaluate the relationship between household income, cortisol, and BMI trajectories in early childhood over three years.
The aforementioned study parameters were measured at baseline, 12, 24, and 36-month follow-up visits( in the NET-works study)
The sample size was 534 children aged 2-4 years with household income < $65,000/year at baseline.
Adjusted linear growth curve model was used to determine the relationships between very low-income (< $25,000/year) at baseline, income status over the time remaining or increasing), cortisol cumulation from hair samples, and BMI percent of the 95th percentile BMIp95) trajectories.
The reference group for all analyses had a baseline income between $25,000-$65,000/year.
The key results of the study are:
• BMIp95 was higher in very low-income household childrens with a p-value of <0.001 compared to the reference group and was recorded as 0.40 vs. -0.62 percentage units/year.
• BMIp95 was more significant in children from households where income remained very low, with a p-value of <0.01 and 0.34 percentage units/year.
• In children with increasing income, the p-value was 0.01 with 0.51 percentage units/year.
• The reference group had -0.61 percentage units per year.
• Hair cortisol accumulations were higher in children where household income remained very-low-income, with 0.22 pg/mg and a p-value of 0.02 compared to the reference group.
• The hair cortisol cumulation in children from households with an increasing income had no significant difference from the reference group, and the value recorded was 0.03 pg/mg.
• There was no relationship between cortisol and BMIp95.
The co-researcher Dr. Crain from Health Partners Institute at Bloomington concluded that "The findings of our study highlight that the children belonging to low-income families are impacted by BMI trajectories and developing stress systems while cortisol and BMI remain independent of each other."
The present study received support from the Eunice Kennedy Shriver National Institute of Child Health And Human Development Of The National Institutes Of Health under award numbers u01hd068990 and r01hd090059.
References:
Kunin-Batson As, Crain Al, Gunnar Mr, Kelly As, Kharbanda Eo, Haapala J, Seburg Em, Sherwood Ne, French Sa. Household Income, Cortisol, And Obesity During Early Childhood: A Prospective Longitudinal Study. J Pediatr. 2022 Sep 13:S0022-3476(22)00808-3.