2.3. Operationalizing Allostatic Load

Researchers conceptualized AL as a cumulative indicator of overall wear-and-tear on the body in response to adapting to environmental stresses [9,10]. AL is used as an antecedent for chronic diseases [9]. The study used the following biomarkers to operationalize AL: total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, glycosylated hemoglobin (HbA1c), albumin (Alb), triglycerides (TG), body mass index (BMI), creatinine clearance (CLCR), C-reactive protein (CRP), systolic blood pressure (SBP), and diastolic blood pressure (DBP). This is consistent with previous studies that have used biomarkers from cardiovascular, metabolic, and immune systems [9,14]. The biomarkers were transformed into quantiles based on the data distribution. The top 25% of the distribution for seven markers: C-reactive protein (CRP), triglycerides (TG), total cholesterol (TC), systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index, and glycosylated hemoglobin, were designated as high risk to determine higher AL. The bottom 25% of the distribution of albumin, creatinine clearance, and HDL cholesterol were also considered high-risk, as a lower value for these markers indicated dysfunction. In forming the index out of 10 for everyone within the study, all high-risk individuals, for each marker were assigned a 1, with non-high-risk individuals given a 0 to obtain a total AL value. An AL value greater than or equal to 3/10 was considered elevated.