Is it true that taking medicines might affect our thinking skills as we age? Professor Karen Ritchie of the National Institute of Medical Research in France guides us through the evidence, as part of our Staying Sharp series.
- Some memory and thinking problems may be caused by certain medications, particularly a group of drugs known as ‘anticholinergics’.
- The effects are more common in older people who have been taking several different anticholinergic drugs over a long period, but many anticholinergics are typically taken for a short time.
- Don’t just cut them out. Many are life-saving. It’s important to weigh up their benefits and be aware of the risks.
- If you have any concerns, talk to your doctor and discuss possible alternatives.
What’s the link between medication and thinking skills?
Much of the decline in memory and reasoning experienced by older people that has been attributed to ageing in the past is now known to be potentially reversible. It’s therefore important always to consider the cause of the decline. Possible causes include dehydration, malnutrition and build-up of fluid as a result of head injury.
Another cause is the long-term use of medications known to have an 'anticholinergic effect'. These 'anticholinergics' interfere with the functioning of a particular neurotransmitter in the brain and nervous system. This neurotransmitter (acetylcholine) is a chemical signal involved in communication between brain cells and it’s known to be central to healthy functioning of thought processes.
What are anticholinergics?
- This is a large group of drugs that are used to treat a wide range of conditions.
- It includes antihistamines, benzodiazepines, some antidepressants, barbiturates and muscle relaxants.
- Examples of conditions that anticholinergics are used for are asthma and COPD, incontinence, insomnia, depression, dizziness, some allergies including hay fever, and peptic ulcers and diverticulitis.
Which anticholinergic drugs are we talking about?
It is well known that an anticholinergic agent, scopolamine, given to young adults reduces activity in the brain areas associated with memory and mimics the slight loss of attention and psychomotor speed seen in normal ageing (psychomotor speed is the speed at which muscles obey commands from the brain).
What is less known is that many commonly prescribed drugs, and some over the counter medications, have similar anticholinergic properties. These drugs include antiemetics, antispasmodics, bronchodilators, antiarrhythmic drugs, antihistamines, analgesics, corticosteroids, muscle relaxants, antihypertensives, antiparkinsonian agents, ulcer drugs and psychotropic medication.
Continuous use of anticholinergics over one year in people over 65 may produce memory impairments that are easily confused with the early symptoms of dementia (for instance, memory loss is often the first sign of Alzheimer’s disease, which is the most common form of dementia). Research has shown that after four years there is a higher risk of actually developing dementia. Further, a study of people taking anticholinergics conducted over six years showed a steady downward decline in their psychomotor speed and reasoning ability.
Importantly, however, research has shown that discontinuation of these drugs can reverse these cognitive effects.
Anticholinergic drugs are commonly prescribed in middle age and the number prescribed to any one individual may increase over time. Moreover, as we age these drugs are likely to have a more pronounced effect on thinking skills as substances pass from the blood stream into the brain more easily and our bodies process drugs more slowly. It is estimated that around 50% of the adult population are taking drugs with anticholinergic properties with 5% of people in nursing homes taking more than 5 of them.
We are all different in the way our bodies respond to drugs, so the effect of anticholinergics won’t be the same in everyone. There is some early evidence from research to suggest the effect may be greater in people who carry a gene associated with Alzheimer’s disease (known as the APOE4 allele). However, it has also been suggested that the anticholinergic effects may be reduced by estrogen levels or those taking hormonal replacement therapy. This research has yet to be confirmed by further studies.
Take a balanced view
Many of the drugs with anticholinergic effects are only taken for short periods, and many are also life-saving. Moreover, their effects are not the same in different individuals.
It is therefore important not to fearfully exclude them but rather to weigh up their benefits and to be aware that they may influence cognitive functioning, especially in older people, in which case alternative medications may be sought.
The effect on cognitive function of these medications is commonly underestimated in general practice, and rarely are memory complaints in later life attributed to their long-term use. It is therefore important to ensure that memory problems appearing in older people are not due to the underlying effects of these medications and to avoid accumulation through long periods of taking of multiple anticholinergics.
If you have any concerns about your medications and their effects, you should always talk to your doctor.
About the author
Professor Karen Ritchie is a Research Director at Inserm, the National Medical Research Institute of France, and a Visiting Professor at Imperial College in London. Her research interests are in the risk of neurological diseases in older people and identifying potentially reversible risk factors for cognitive decline.
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*A list of commonly used anticholinergic drugs may be found in this paper.