Coffee consumption and healthy ageing – Can coffee protect against age-related cognitive decline?

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Expert comment from Karen Ritchie, BSc, MPsych, PhD
Research Director, French National Institute for Health and Medical Research
Honorary professor Dept of Public Health, Imperial College, London

Approximately 26 million people suffer from Alzheimer’s disease worldwide, making it the most prevalent form of dementia.  [1] The incidence of Alzheimer’s increases dramatically with age, and 20% of the European population will be over 65 by 2025.[2] These conditions make it all the more urgent to find ways to alleviate symptoms and ultimately, cure the disease itself.

In science one of the dilemmas at present is that there are still many forms of cognitive decline that we cannot explain, including dementias and above all, Alzheimer’s disease.  This is where epidemiologists step in. What we can do is to compare the population who are sick and those who are healthy, to identify genetic, biological and environmental risk factors influencing people’s tendency to suffer cognitive decline. Over the last 20 years we have identified many factors that can in fact delay the onset of the disease – now we are investigating whether they can be used in a preventive way. At our research centre in Montpellier, using a large population study we have been able to identify the most significant modifiable factors in the onset of dementia. Certain factors stand out – particularly diabetes, depression, diet, stroke and ApoE4; which is the main genetic factor. Diet is crucial among them, and although diets differ in different parts of the world, an international common feature is often coffee consumption.

Coffee was once thought of as a psycho-stimulant – a temporary solution to pick ourselves up intellectually. In fact Tiramisu, the coffee-based Italian dessert, literally means ‘pick me up’!  This perception started to change as the body of evidence grew on the relationship between coffee and cognitive decline. And the relationship between coffee, cognitive functioning, and dementia has turned out to be particularly interesting.

A significant milestone in changing perceptions happened when colleagues, who were working with transgenic mice, found that those who were fed caffeine had lower levels of amyloid plaques, which are little plaques that accumulate in the brain with Alzheimer’s disease and are also present in people who present rapid cognitive decline, even though they might not develop Alzheimer’s disease.[3] There were a number of small studies after that.

Turning back to our research centre, we found a dose-responsive effect of caffeinated coffee on cognitive decline, exclusively in women.  No marked effect could be observed on women who consumed less than 1 mg of caffeine a day. We found a reduction in signs of cognitive decline of approximately 20% in women consuming 1 – 2 mgs, and more strikingly women having 3 mgs and more a day displayed up to 50% improvement. With age, effects seemed to become stronger.[4],[5]

At this point, it is important to note that in epidemiology we show associations, but are we really showing cause and effect? Not necessarily. In our case, the missing link was likely to be found in our biological hypothesis – in other words, whether the number of amyloid plaques really had a direct causal relationship with the development of Alzheimer’s disease.

A hint to the answer came at the occasion of a similar conference in Costa Rica. After the presentation of my research, a scientist who had been sitting in the assembly came to find me. He pointed out that our team of researchers seemed to have overlooked an essential fact: coffee beans constitute one of the richest sources of oestrogen. Things started to make more sense; our hypothesis should be oriented toward hormonal changes derived from coffee consumption. Could it be that women not taking hormonal replacement therapy at the time of menopause were benefiting from coffee intake as a form of benign hormonal treatment?

This idea could explain why women under drug-based hormonal therapy did not seem very responsive to coffee intake: because the effects were masked by hormonal therapy that was doing the same thing.

What conclusion can be drawn from this? Evidence so far suggests there really is a strong effect of coffee consumption in reducing cognitive decline over time in women. We still ignore whether on the long term, we are going to observe a reduction in the number of cases of Alzheimer’s disease, but it seems highly likely that there is a cause and effect relationship.

[1] Alzheimer Europe (2010) ‘The impact of Alzheimer’s disease in Europe’ Available at http://www.alzheimer-europe.org/EN/Research/PharmaCog/Why-PharmaCog/(language)/eng-GB
[2] Alzheimer Europe (2010) ‘The impact of Alzheimer’s disease in Europe’ Available at http://www.alzheimer-europe.org/EN/Research/PharmaCog/Why-PharmaCog/(language)/eng-GB
[3] Dall’ Igna O P, Fett P, Gomes M W, Souza D O, Cunha R A, Lara D R (2007), Caffeine and adenosine A2a receptor antagonists prevent β-amyloid (25-35)-induced cognitive deficits in mice, Experimental Neurology, Vol. 203, pp. 241 – 245.
[4] Artero S, Van Boxtel M, Dartigues JF, Deeg D, Dick M, Frisoni G, Galluzzo L, Jolles J, Jonker C, Luck T, Peres K, Riedel-Heller S, Ritchie K, Sacuiu S, Scafato E, Skoog I, Schoevers R, Verhey F, Jelle Visser P (2008), P4-004: Risk factors for progression to dementia in general population: The diagnostic criteria for predementia Alzheimer’s disease (Descripa) study (European pooled data base), Alzheimer’s & Dementia, Vol. 4, n. 4, Supplement, pp.  T667-T668.
[5] Ryan J, Carrière I, Carcaillon L, Dartigues JF, Auriacombe S, Rouaud O, Berr C, Ritchie K, Scarabin PY, Ancelin ML (2014), Estrogen receptor polymorphisms and incident dementia: The prospective 3C study, Alzheimer’s & Dementia, Vol. 10, n. 1, pp 27-35.

 

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