Introduction
Caffeine is frequently consumed to boost goal-directed attention. These procognitive effects may occur due to the adenosine-mediated enhancement of monoamines, such as dopamine, after caffeine administration. As such, caffeine’s beneficial effects may be altered in conditions such as Parkinson’s disease (PD). However, whether caffeine improves cognition, and at what cost, has not been experimentally established in patients with neurodegenerative disease.
Methods
Single-dose trials to probe cognitive effects of caffeine are often confounded by short-term caffeine abstinence which conflates caffeine’s effects with treatment of withdrawal. Using a placebo controlled, blinded, randomised trial design, we assessed the effect of 100 mg of caffeine across well-established tasks (Choice reaction time, Stroop Task and Rapid Serial Visual Presentation Task; RSVP) that probe different aspects of attention in PD patients (n = 24) and controls (n = 44). Critically, participants withdrew from caffeine for a week prior to testing to eliminate the possibility that withdrawal reversal explained any cognitive benefit.
Results
Caffeine administration was found to reduce the overall number of errors in patients and controls on the Stroop (p = .018, η2p = .086) and Choice reaction time (p < . 0001, η2p = .588) tasks, but there was no specific effect of caffeine on ignoring irrelevant information in the Stroop task. On the RSVP task, caffeine improved dual item accuracy (p = .037) but impaired single item accuracy (p = .044). Across all tasks, there was little evidence that caffeine has different effects in PD participants and controls.
Conclusion
When removing withdrawal effects as a factor, we demonstrate caffeine has beneficial effects on selective attention but is a double-edge sword for visual temporal attention and would need careful targeting to be clinically useful.
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BackgroundLapses in attention are a debilitating feature of Dementia with Lewy Bodies (DLB). Caffeine is the most widely consumed stimulant worldwide however its potential to ameliorate attention impairment in healthy ageing and neurodegenerative disease is unknown. In this study we explore whether caffeine will improve performance attention in older participants without cognitive disorder and those with DLB.Methods30 healthy elderly participants and 6 people affected by DLB performed a blinded, placebo-controlled, cross-over study using a battery of cognitive tasks including simple and choice reaction time, attentional blink, Stroop, digit span and walking while talking tasks. Participants initially abstained from caffeine for 7 days before cognitive testing on day 8 with a caffeinated (100 mg) or de-caffeinated drink 1 hour prior to testing. On day 9 the alternative drink was received.ResultsData from healthy elderly participants demonstrates caffeine reduces digit span (p=0.027) and delays the attentional blink (p=0.01), but in contrast improves choice reaction time (p=0.03) and Stroop task performance (p=0.042), with no clear effects yet in DLB group.DiscussionIn healthy older people, caffeine can boost performance on simple and complex attentional tasks and alter the temporal dynamics of attention but at a cost to working memory.
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