To assess the effect of sex and age on plasma neurofilament light (NfL) and glial fibrillary acidic protein (GFAP) levels in a healthy control (HC) cohort.

Blood NfL levels vary with age and comorbid disorders. The effect of age on blood GFAP has not been investigated.

HC subjects without neurologic disease, cancer, diabetes, and traumatic brain injury were recruited from community and wellness events. Plasma NfL and GFAP were measured using the SR-X Simoa Quanterix platform. Changes in biomarker levels per year of age were estimated and log-linear predictive models generated.

110 of 155 HC samples have been analyzed to date. Age ranges from 16.4 to 59.6 years with the following distribution: 15-19 (11.82%), 20-30 (36.36%), 30-40 (21.82%), 40-50 (15.45%) and 50-60 (14.55%). Sex and racial distribution were female (64.5%), White (78.2%), 15.5% Hispanic, 7.4% Black, 5.5% Asian, 0.9 % American Indian, 1.8 % other. Geometric mean NfL concentrations increased by age, ranging from 2.47 pg/ml (CI: (1.87, 3.29) at 15-19 years to 7.22 pg/ml (CI: (5.97, 8.73) at 50-60 years. Geometric mean GFAP values increased from 49.99 pg/ml (CI: (41.74, 59.87) at 15-19 years to 72.56 pg/ml (CI: (60.16, 87.51) at 50-60 years. Adjusting for age and gender, expected NfL values increased by 2.57% per year (95% CI: (1.90%, 3.25%), p < 0.0001) overall, 2.72% (95% CI:(1.96%, 3.49%), p < 0.0001) in females, and 2.22% (95% CI:  (0.87%, 3.58%), p = 0.0018) in males.  Expected GFAP increased by 0.94% per year (95% CI:  (0.26%, 1.62%), p = 0.0067) overall and by 0.95% (95% CI:  (0.11%, 1.80%), p = 0.0273) in females.

Utilizing more stringent criteria for HC, our study replicates recent reports on blood NfL levels using national cohorts and provides novel data of plasma GFAP levels across a broad age distribution.