MENTAL PERFORMANCE
In the same 1992 review (1) it was concluded that “When caffeine is consumed in the range of doses found in many foods, it improves the ability of individuals to perform tasks requiring sustained attention, including automobile driving. In addition, when administered in the same dose range, caffeine increases self-reported alertness and decreases sleepiness”. “Adverse behavioural effects occur when caffeine is consumed in excessive doses or by individuals who are overly sensitive to the substance”.
More recent work has confirmed these conclusions. Thus caffeine increases the processing of new stimuli (2), enhances target detection and response preparation (3) and increases the amount of information processed (4). Such improvements in mental performance are likely to have important implications for the performance of every day tasks. Thus caffeine improved both performance on a driving simulator and during laboratory tests of attention (5). Mental performance declines with age. A cross-sectional study of 890 women and 638 men, mean age 73 years, looked for associations between cognitive function as measured by 12 standardised tests and lifetime or current coffee consumption (6). A higher lifetime coffee consumption in women was significantly associated with better mental performance in six tests. Recently published studies have demonstrated that coffee drinking reduces cognitive decline in both men and women. Van Gelder et al (7), examined whether coffee consumption was associated with 10-year cognitive decline in elderly men. The study participants were 676 healthy men born between 1900 - 1920 from Finland, Italy and the Netherlands. The authors concluded that 'Findings suggest that consuming coffee reduces cognitive decline in elderly men. An inverse and J-shaped association may exist between number of cups of coffee consumed and cognitive decline, with the least cognitive decline for men consuming 3 cups of coffee per day'. Similar findings were reported for women in a study that examined the association between caffeine intake, cognitive decline and dementia in a community based sample of subjects aged 65 years and over(8). The participants were 4,197 women and 2,820 men from a population cohort recruited from three French cities. Cognitive performance, clinical diagnosis of dementia, and caffeine consumption caffeine consumption were evaluated at baselineand at 2 and 4 year follow-up. The authors found that the psychostimulant properties of caffeine appeared to reduce cognitive decline in women without dementia, especially at higher ages. Interestingly, unlike Van Gelder, these researchers found no relation between caffeine intake and cognitive decline in the male participants of thier study.
References:
1. Liebermann, H.R. Caffeine. In: Smith, A.P. and Jones, D.M. (Eds.), Handbook of Human Performance, vol. 2. Academic Press, London, pp. 49-72, 1992.
2. Smith, A.P. et al. Physiology and Behavior, 67, 9-17, 1999.
3. Lorist, M.M. and Snel, J. Electroencephalography and Clinical Neurophysiology, 102, 401-413, 1997.
4. Ruijter, J. et al. Journal of Psychophysiology, 13, 37-48, 1999.
5. Brice, C. and Smith, A.P. Human Psychopharmacology, 16, 523-531, 2001.
6. Johnson-Kozlow, M. et al. American Journal of Epidemiology, 156, 842-850, 2002.
7. Van Gelder,B.M. et al, European Journal of Clinical Nutrition, 61, 226-232, 2007.
8. Ritchie, K, et al. Neurology, 69, 2007.