Dehydration Impairs Executive Function Task in Middle‐Age and Older Adults Following Endurance Exercise

Abstract

Dehydration attenuates exercise and cognitive function performance in younger adults, but less is known about the impact of dehydration on the aging population. Regular exercise serves as a robust prophylactic treatment to prevent age‐related decline in physical and cognitive function. However, middle‐age and older adults often display a blunted thirst perception, which places them at risk for dehydration and subsequently may reduce the cognitive health‐related benefits of exercise.PURPOSETo examine the impact that pre‐exercise hydration status has on executive function task following endurance exercise within a middle‐age and older adult cohort.METHODSThis field study was conducted at a mass participation cycling event in Wichita Falls, Texas (ambient temperature, 26°C mean, 30°C maximum; relative humidity, 75% mean, 93% maximum). Forty‐nine recreational cyclists (55±6 y, range 44–70y) were enrolled following informed consent and were retrospectively separated into 2 groups (euhydrated, EUH; dehydrated, DEH) based on pre‐exercise hydration status. Criteria for euhydration were consistent with sports medicine consensus guidelines (urine specific gravity <1.020, Usg; urine color < 4 units, Ucol). All cyclists were screened for mild cognitive impairment via the validated Mini‐Cog™ assessment (4±1). At baseline, participants were familiarized with the executive function pencil‐paper test (Trail Making A and B Tests, TMT) and anthropometric measurements were recorded. Cyclists completed the TMT prior to and immediately following the event. Ratings of perceived exertion (RPE) and total exercise time were determined at the finish line. Pre‐ and post‐TMT scores were compared via paired T‐test and Cohen d effect size were recorded. All the following data are presented as mean±SD.RESULTSGroups (EUH vs DEH) did not differ in age (55±5 vs 54±8 y) or body fat percentage (12.8±5.6 vs 14.5±5.1) (p>0.05). Significant differences were note in both Usg (1.015±0.004 vs 1.023±0.002) and Ucol (3±1 vs 5±1) (p<0.001). Post exercise RPE (15±2 vs 17±2), total event time (362±59 vs 359±51 min), and body mass loss ( −2.0%, EUH and DEH) were similar for both groups (p>0.05). After the HHH 164‐km endurance cycling event, there was a significant improvement (i.e., faster completion time) in the TMT noted in the EUH group (pre vs post, 83±24 vs 71±18 s; p<0.05) but not the DEH group (pre vs post, 86±26 vs 79±22 s). Further analysis showed the Cohen d effect sizes to be moderate (0.5) in the EUH and small (0.2) in the DEH group.CONCLUSIONIn this prospective study, dehydration negatively impacted an executive function task (TMT) in middle‐age and older adults following an acute bout of prolonged, moderate‐intensity endurance exercise. This suggests that older adults should adopt adequate drinking behaviors to reduce cognitive fatigue and potentially enhance the cognitive benefits of regular exercise participation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.