Effects of resistance exercise and whey protein supplementation on cognitive function in older men: secondary analysis of a randomised, double-blind, placebo-controlled trial

Purpose: Ageing is associated with cognitive decline. This study investigated the individual and combined effects of resistance exercise (RE) and whey protein supplementation (PRO) on cognitive function in older men. Methods: In a pooled-groups analysis, 36 older men (age: 67 +/- 4 years) were randomised to either RE (2 x/week; n = 18) or no exercise (NE; n = 18), and either PRO (2 x 25 g/d whey protein isolate; n = 18) or control (CON, 2 x 23.75 g maltodextrin/d; n = 18). A sub-analysis was also conducted between RE + CON (n = 9) and RE + PRO (n = 9). At baseline and 12 weeks, participants completed a battery of neuropsychological tests (CANTAB; Cambridge Cognition, UK) and neurobiological, inflammatory, salivary cortisol and insulin sensitivity biomarkers were quantified. Results: PRO improved executive function z-score (+0.31 +/- 0.08) greater than CON (+0.06 +/- 0.08, P = 0.03) and there was a trend towards improved global cognitive function (P = 0.053). RE and RE + PRO did not improve any cognitive function domains (p >= 0.07). RE decreased tumor necrosis factor-alpha (P = 0.02) and interleukin-6 (P = 0.048) concentrations compared to NE, but changes in biomarkers did not correlate with changes in cognitive domains. Muscle strength (r = 0.34, P = 0.045) and physical function (rho = 0.35-0.51, P < 0.05) outcomes positively correlated with cognitive function domains at baseline, but only Delta skeletal muscle index correlated with Delta episodic memory (r = 0.34, P = 0.046) following the intervention. Conclusion: In older men, PRO improved cognitive function, most notably executive functioning. RE did not improve any cognitive function domains but did decrease biomarkers of systemic inflammation. No synergistic effects were observed.