How coffee and tea can help lower the risk of stroke and dementia

16Dec 2021
The Guardian
How coffee and tea can help lower the risk of stroke and dementia

Dementia manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behaviour, which negatively impact a person's ability to function and carry out everyday activities.

Aside from memory impairment and a disruption in thought patterns, the most common symptoms include emotional problems, difficulties with language, and decreased motivation. The symptoms may be described as occurring in a continuum over several stages. Dementia is not a disorder of consciousness, as that is not usually affected. It ultimately has a significant effect on the individual, caregivers, and relationships in general.

A diagnosis of dementia requires a change from a person's usual mental functioning and a greater cognitive decline than what is caused by normal aging. Several diseases and injuries to the brain, such as a stroke, can give rise to dementia.

Whereas astroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functioning properly. Signs and symptoms of a stroke may include an inability to move or feel on one side of the body, problems understanding or speaking, dizziness, or loss of vision to one side. Signs and symptoms often appear soon after the stroke has occurred. If symptoms last less than one or two hours, the stroke is a transient ischemic attack (TIA), also called a mini-stroke. A hemorrhagic stroke may also be associated with a severe headache. The symptoms of a stroke can be permanent. Long-term complications may include pneumonia and loss of bladder control.

The main risk factor for stroke is high blood pressure. Other risk factors include high blood cholesterol, tobacco smoking, obesity, diabetes mellitus, a previous TIA, end-stage kidney disease, and atrial fibrillation.

At least two cups of tea or coffee are needed to see an effect, said the study, published in the journal Plos Medicine recently. The research project, carried out by researchers at Tianjin Medical University in China, included 365,682 participants from the UK Biobank study.

“Our findings suggested that moderate consumption of coffee and tea separately or in combination were associated with lower risk of stroke and dementia,” the study authors wrote. People who drank two to three cups of coffee or three to five cups of tea a day, or a combination of four to six cups of coffee and tea had the lowest incidence of stroke or dementia, the researchers found.

Those who drank two to three cups of coffee and two to three cups of tea daily had a 32 per cent lower risk of stroke and a 28 per cent lower risk of dementia compared with those who did not drink tea or coffee.

The research, led by Yuan Zhang, further suggests that the intake of coffee alone or in combination with tea is associated with a lower risk of post-stroke dementia. Researchers studied the 365,682 participants between 2006 and 2010 and followed them until 2020. At the start, participants self-reported how much coffee and tea they drank.

Over the study period, 5,079 participants developed dementia and 10,053 experienced at least one stroke. However, the scientists pointed out that the UK Biobank reflects a relatively healthy sample in relation to the general population, which could restrict the ability to generalise.

In addition, few people in the study developed dementia or stroke, which could make it difficult to extrapolate rates accurately for larger populations. Finally, while it is possible that coffee and tea consumption may be protective against stroke, dementia and post-stroke dementia, researchers say causality cannot be concluded from the associations.

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