Study participants

In an effort to span a broad cross-section of the North American population, 32 healthy volunteers (16 male; 16 female) were recruited from the Charles Village, Hampden, and Roland Park neighborhoods in Baltimore, Maryland. All prospective participants were verbally screened to exclude those with any history of neurological injury/disease, psychiatric disorder, metabolic disease (including diabetes), autoimmune disorder, or substance abuse (including alcohol and/or tobacco). Of the 32 subjects, 19 were Caucasian, 9 were Asian, 2 were African-American, and 2 were Hispanic (based on self-report). Age and body composition measures for these participants are shown in Figure ​Figure11 and Figure S1. This study was approved by the Johns Hopkins University (JHU) Institutional Review Board, and all participants provided written informed consent prior to enrollment.

Age and body composition data. (A) Box and whisker plots of Body Mass Index (BMI), Body Fat Percent (BFP), and Age among the 32 healthy study participants, as well as linear correlations (r) and statistical significance values (p) between: (B) normalized BMI and Age, (C) normalized BFP and Age, and (D) normalized BFP and BMI. (E) Partial correlations (r_p) were also performed between normalized BFP and normalized BMI to factor out the effects of age and gender.