Background and aim: How cortisol, a stress biological marker, differs according to depressive symptoms has mostly been examined in high-income countries. Including low- and middle-income countries in research on this matter would allow examining a wider range of exposure to adversity and improving the estimates of the associations between diurnal cortisol and depression. The aim of this study is to compare the profile of diurnal cortisol and depressive symptoms in 65- to 74-year-old residents of Santa Cruz (in an underdeveloped region, northeast Brazil, n = 64) and Saint-Bruno (a suburban area, QC, Canada, n = 60).
Methods: Home interviews included assessments of socioeconomic variables, health behaviors, depressive symptoms (Center for Epidemiologic Studies Depression Scale, CES-D) and Cortisol Awakening Response (CAR: awakening, 30, 60 min afterward), and at 1500 hours and bedtime from saliva collected over 2 days. Mixed linear models were used to estimate the associations between diurnal cortisol and depressive symptoms.
Results: Santa Cruz residents had lower cortisol levels upon awakening (β = -1.24, p = 0.04) and elevated bedtime levels (β = 20.29, p < 0.001) indicating chronic stress compared to Saint-Bruno residents. Elevated depressive symptoms were associated with a blunted CAR (flatter slope, indicative of chronic stress) in Santa Cruz residents (β = -0.19, p = 0.04), while greater diurnal cortisol levels (larger area under the curve), indicative of moderate stress, were observed in Saint-Bruno residents (β = 1.96, p = 0.047).
Conclusion: Adverse living conditions in this remote area of Brazil may lead to a state of chronic stress and a different relationship with elevated depressive symptoms from persons aging in a Canadian suburban area.