Table 3.

Effect of age on intracellular glutathione and plasma biomarkers of oxidative stress and oxidant damage. Data are reported as multiple regression estimates (95% confidence intervals) adjusting for cohort, age group, and sex. p-values adjusted for multiple hypothesis tests using Bonferroni correction within each outcome measure. Means are significantly different at p < 0.05. YA = young adults (21–40 years), YA-C = young adults with COVID-19 (21–40 years); MA = middle-aged adults (41–60 years), MA-C = middle-aged adults with COVID-19 (41–60 years); OA = older adults (≥60 years), OA-C = older adults with COVID-19 (≥60 years).

Physical Function	Young Adults (21–40 years)	Young COVID-19 Patients (21–40 years) YA vs. YA-C YA-C vs. OA-C	Middle-Aged Adults (41–60 years)	Middle-Aged COVID-19 Patients (41–60 years) MA vs. MA-C MA-C vs. YA-C	Older Adults (≥60 years)	Older COVID-19 Patients (≥60 years) OA vs. OA-C OA-C vs. MA-C
RBC-total GSH (mmol/L.RBC)	1.8 (1.7, 1.9)	0.7 (0.7, 0.8) p < 0.0001 p < 0.0001	1.1 (1.0, 1.3)	0.3 (0.3, 0.4) p < 0.0001 p < 0.0001	0.8 (0.6, 0.9)	0.3 (0.2, 0.4) p < 0.0001 p > 0.99
RBC-reduced GSH (mmol/L.RBC)	1.7 (1.6, 1.8)	0.7 (0.6, 0.7) p < 0.0001 p < 0.0001	1.0 (0.9, 1.1)	0.3 (0.2, 0.3) p < 0.0001 p < 0.0001	0.4 (0.3, 0.5)	0.2 (0.1, 0.3) p = 0.036 p > 0.99
RBC-GSSG (mmol/L.RBC)	0.2 (0.1, 0.2)	0.1 (0.0, 0.1) p = 0.09 p > 0.99	0.1 (0.0, 0.2)	0.1 (0.0, 0.1) p > 0.99 p > 0.99	0.4 (0.3, 0.5)	0.1 (0.0, 0.1) p < 0.0001 p > 0.99
RBC GSH/GSSG ratio	10.0 (4.9, 15.0)	14.7 (11.5, 17.8) p = 0.8 p < 0.0001	16.7 (11.0, 22.3)	3.7 (0.6, 6.8) p = 0.001 p < 0.0001	1.9 (0, 7.0)	2.5 (0, 5.7) p > 0.99 p > 0.99
Plasma TBARS (μM/L)	2.4 (0, 5.9)	18.1 (15.9, 20.3) p < 0.0001 p < 0.0001	2.7 (0, 6.6)	29.9 (27.8, 32.1) p < 0.0001 p < 0.0001	23.2 (19.7, 26.7)	39.6 (37.3, 41.8) p < 0.0001 p < 0.0001
Plasma F2-isoprostane (pg/mL)	45.4 (23.5, 67.4)	162.3 (148.5, 176.0) p < 0.0001 p < 0.0001	49.7 (25.2, 74.3)	195.9 (182.4, 209.4) p < 0.0001 p = 0.006	190.1 (168.2, 212.1)	259.8 (245.6, 274.1) p < 0.0001 p < 0.0001