Caffeine and Cognitive performance
Unhealthy lifestyles, vascular diseases, genetic factors, oxidative stress and inflammation all accelerate cognitive decline and suggest that cognitive decline could, at least partly, be modifiable. It has been hypothesized that caffeine could, in part, compensate for this decline because of its effects on vigilance, mainly in situations of reduced alertness80-83. However, young and elderly subjects appear to respond to the effects of caffeine differently.
Two early studies on both elderly and adult subjects found that caffeine improves attention span, psychomotor performance and cognitive function, as well as and feelings of well-being in the elderly. The elderly appeared more sensitive to the protective effects of caffeine on declining mental performance over time than younger subjects1,2.
In younger subjects (18-37 years), caffeine has been shown to improve performance during distraction, rather than during simple tasks. In elderly subjects (60-75 years) however, caffeine improved performance during more complex tasks requiring sustained attention. Interestingly, improving performance during complex tasks is usually less effective in elderly subjects than in younger participants3. It is suggested that caffeine may help to reverse the effects of cognitive aging by stimulating the energy resources of elderly subjects4.
A British study of 9,003 adult subjects reported a dose-related improvement in cognitive performance with higher levels of coffee consumption. Higher overall caffeine consumption (from coffee and tea) improved simple and choice reaction times, incidental verbal memory and visuo-spatial reasoning. Older people appeared more susceptible to the performance-enhancing effects of caffeine on mental performance than younger subjects5.
Analysis from the Baltimore Longitudinal Study of Aging, a prospective cohort study, also suggested that caffeine intake was associated with better baseline cognition in adults over 70 years of age6. Two Dutch studies on subjects aged 24-81 years also found positive effects of caffeine on cognition, mainly reaction time and verbal memory, but no age-related were observed7,8.
Other components in coffee may also enhance cognitive performance in older adults. A pilot study on 39 healthy participants, aged 53-79 years, found that decaffeinated coffee enriched with chlorogenic acids improved mood and some mood-related behaviours, compared to regular decaffeinated coffee. The effect was less robust than the one triggered by caffeine, but reflects the potential cognitive-related activity of chlorogenic acids and warrants further investigation9.
Effects of coffee on cognitive decline
Further studies have considered the specific effect of coffee consumption, suggesting that habitual coffee consumption may boost the cognitive reserve of older adults, particularly in women.
A 2010 meta-analysis which included 9 studies which looked at the effects of coffee/caffeine on different measures of cognitive impairment and/or decline (four studies on Alzheimer’s disease; two on dementia or cognitive impairment; three on cognitive decline), found a reduced risk of cognitive decline across different measures of cognitive impairment (mean risk ratio 0.84) with caffeine intake, with moderate heterogeneity10. Although the outcome of this meta-analysis ranged from cognitive decline to Alzheimer’s disease, the analyses showed a clear protective role of coffee. However, it should be noted that many papers devoted to the effects of coffee on age-related cognitive decline were not included in this review.
A further systematic literature review published in 2013 found only six prospective studies that encouraged further study of decline across the spectrum of cognition. The review suggested that, for all studies on tea and most of those on coffee, estimates of cognitive decline were lower among consumers but there was no evidence of a dose response. Research has also suggested a stronger effect in women than men11.
However, a 2018 meta-analysis of prospective studies indicated no statistically significant association between coffee consumption and the risk of dementia12.
A number of large studies have also considered associations between coffee intake and cognitive decline.
- The Rancho Bernardo study with 1,538 participants – 890 healthy women and 638 healthy men from South California with a mean age of 73 years – reported that higher caffeine consumption in a lifetime was associated with better performance in women in 6 out of 12 cognitive tests, with a trend in two other tests. Among women aged 80 or older, lifetime coffee intake was associated with better performance in 11 out of 12 tests. Current caffeinated coffee intake was also associated with improved performance. No relation was found between coffee intake and cognitive function in men, or between decaffeinated coffee intake and cognitive function in either sex13.
- The longitudinal prospective Three City cohort study of 4,197 healthy women and 2,820 healthy men over 65 years, suggested that women consuming more than 3 cups of caffeinated coffee per day for 4 years showed a smaller decline in verbal retrieval and visuo-spatial memory than women consuming one cup of coffee or less per day. The protective effect of caffeine increased with age, with a maximal effect in women over 80 years. No relation was found between caffeine intake and cognitive decline in men14.
- A cohort of 648 adults aged 65 years old and living in Portugal, with a caffeine intake of more than 62 mg/day (the equivalent of 1 regular cup or more) compared to less than 22 mg/day was associated with a lower risk of cognitive decline in women only15.
- Another study of 4,809 participants aged 65 and older suggested that subjects who did not consume tea or coffee declined mentally every year by 1.30 points (women) and 1.11 points (men) on standard scores. In fully adjusted models, tea, coffee or caffeine consumption modestly attenuated the rate of cognitive decline in women, with no consistent effect on men16.
- A further prospective study looked at the 10-year cognitive decline of 676 healthy men born between 1900 and 1920 in three European countries (Finland, Italy and The Netherlands). Men who consumed coffee experienced a 10-year cognitive decline of 4%. Non-coffee drinkers experienced an additional decline of 4.7%. The authors reported an inverse J-shaped curve between the number of cups of coffee consumed and the extent of cognitive decline, with the lowest cognitive decline (2%) reported for 3 daily cups of coffee. This decline was 4.3 times smaller than in non-coffee drinkers17.
- A cohort study of 923 healthy adults from Scotland (Lothian Birth Control 1936 Study), assessed the IQ of children at 11 years old and latterly at the age of 70. The authors found association between total caffeine intake (through coffee, tea, and dietary caffeine) and general cognitive ability and memory. After adjustment for IQ at age 11 and social class, a robust positive association remained between drinking ground coffee (filter or espresso) and reading performance. No gender effects were observed, contrary to several previous studies18.
- A general survey performed in Taiwan found that among all lifestyle factors examined, there was an inverse relationship between cognitive impairment and the intake of vegetables and fruits, coffee, and tea. The authors considered that the subjects who did not drink coffee were at a significantly higher risk of cognitive impairment19.
- Further work as part of the Women’s Antioxidant Cardiovascular Study showed that consumption of caffeinated coffee but not other caffeinated products such as tea, cola and chocolate, was significantly related to slower cognitive decline in older women with vascular disorders20.
Research suggests that regular coffee/caffeine consumption can help to reduce cognitive decline in older adults, particularly women. Further research is required to clarify the differences between men and women, and potential mechanisms.
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