Whether in your morning espresso, followed by an English breakfast with your toast, or a quick cup of instant between meetings, a moderate amount of caffeine throughout the day is associated with a reduced risk of worsening dementia.
A new study has now confirmed a link between caffeine intake and spinal fluid markers for Alzheimer's disease.
Most previous research has focused on observational studies or meta-analyses on the consumption of tea and coffee, with comparatively little insight gathered on the biological changes caffeine delivers.
A team in France looked at data from a prospective study that evaluated patients with mild cognitive impairment or Alzheimer's between 2010 and 2015.
Their analysis of 263 participants aged over 70 included a baseline clinical evaluation and a detailed survey of consumption of foods and beverages such as coffee, chocolate, tea, and soda to assess the amount of caffeine absorbed by their bodies each day. Volunteers also had MRI scans taken, and provided samples of blood and cerebrospinal fluid (CSF).
Those who consumed an average of just over 200 milligrams of caffeine per day were grouped into a 'low' caffeine sample, with those who drank more considered to be higher caffeine consumers.
The difference amounts to a can of energy drink or a cup or two of coffee a day, versus several cans or cups respectively – a distinction that could impact the pathology responsible for dementia.
The team found lower caffeine consumption correlated with a higher risk of mild cognitive decline with impaired memory, compared with higher caffeine consumption.
In fact, those in the low-caffeine consumption group were nearly 2.5 times more likely to have a diagnosis of mild cognitive impairment with impaired memory or Alzheimer's.
A closer look at proteins in the participants' spinal fluid also revealed significant differences in ratios and concentrations of specific forms of beta-amyloid proteins. Those who drank less caffeine tended to have lower concentrations of a soluble form called Aβ42, with reduced ratios of Aβ42 with another form called Aβ40.
They also had a reduced ratio between Aβ42 and a form of tau protein called ptau-181 than those who drank higher levels of caffeine.
Taken together, these specific protein levels in the CSF among those who consumed less caffeine signify increased clumping of beta-amyloid proteins in the brain, which is a biological hallmark of the neurodegeneration responsible for Alzheimer's symptoms.
Oddly, the amount of caffeine consumed didn't seem to affect levels of tau protein, which are also known to increasingly accumulate in brain tissue as Alzheimer's symptoms worsen.
Research on caffeine's effects on tau in the brain has been limited, though one laboratory study has indicated it could reduce the chemical activity that causes the protein to 'tangle' in toxic clumps. Yet whether this occurs in cases of Alzheimer's isn't clear.
This latest investigation is based on a mere snapshot of caffeine habits among a few hundred older individuals, so says little about how a morning coffee throughout your youth or middle age might affect the emergence of dementia later.
Consideration needs to be taken for when and how caffeine is consumed. Drinking it late in the day could impact sleep, for example, which also seems to impact long-term neurological functioning. Relying heavily on chocolate and energy drinks comes with an added load of sugar, which also puts cognitive health at risk.
Taken together with the growing pile of research on the relationship between caffeine and health in general, however, it's a solid bet that your morning Earl Gray, midday latte, and small afternoon chocolate snack might play a role in keeping your body working for many years to come.
This research was published in Alzheimer's & Dementia.