HAVE you forgotten where you put your cellphone or did you have difficulty trying to recall the name of the person who just greeted you? As the population here gets increasingly older, medical advances that prolong longevity and preserve one's power of memory become ever more significant.
Dementia is more common among older people, but while many believe it is an inevitable consequence of ageing, medical science has taught us that it is not always so. Do not worry when you have transient lapses in memory. However, understanding more about the mechanisms of memory loss can enable one to take proactive measures to prevent a deterioration in one's power of memory. Having a checklist of the preventable causes of memory impairment will make taking such appropriate preventive measures easier.
Drugs that poison memory
First on the checklist are drugs.
Among those widely consumed that can cause memory impairment are cholesterol-lowering drugs called statins.
A debate is now raging about whether statins have an adverse impact on memory, but in 2012, the USA Food and Drug Administration issued a warning that a small percentage of patients who consume statins can have transient memory loss or confusion, which resolve when they stop taking the drug.
The most vivid example of this was a middle-aged patient of mine whom I had started on a statin. A month later, he expressed concern that he had become forgetful; he was forgetting where he had put his car keys, appointments he had made and even the names of friends.
When he stopped taking the statin, his memory returned. As he was not on any other new medication, the statin was identified as the cause of his forgetfulness.
Fortunately, statin-related memory lapses are rare and reversible.
Other drugs that can affect the memory include first-generation antihistamines such as chlorpheniramine and diphenhydramine, strong narcotic painkillers, antidepressants, anti-anxiety pills and sleeping medication.
Among the blood pressure drugs, beta-blockers may also affect the memory.
If you notice lapses in your short-term memory, discuss with your physician about changing the medication.
Next on the checklist are procedures that can potentially cause memory impairment.
These involve the insertion of plastic tubes (catheters) into the heart arteries through the leg or wrist arteries (a procedure called a coronary angiogram), or into the neck arteries (carotid angiogram). These do carry a real risk of dislodging cholesterol (emboli) from the accumulated deposits (plaques) from the walls of the arteries when the tip of the catheter comes into contact with these plaques and disrupts the lining of the plaques.
These cholesterol emboli can then travel along the blood stream into the brain arteries and cause minor "silent" strokes, which are a contributory cause of cognitive deterioration. At least six studies have demonstrated a "silent stroke" risk of 5 to 22 per cent following invasive coronary angiograms.
Surgical procedures that involve the heart, such as a heart artery bypass graft or heart valve surgery, are also associated with silent strokes and cognitive impairment. Surgery entailing several hours of general anaesthesia may result in short-term memory impairment.
Therefore, for tests that are mainly for diagnosis rather than for the treatment of a medical condition, you should always consider a non-invasive alternative such as magnetic resonance imaging or a computed tomography scan, rather than an invasive test that entails the insertion of tubes into your heart or neck arteries.
For surgery, always discuss with your doctor about minimising the options and also the period of anaesthesia.
Checking on your health is essential when your memory is not as good as it used to be. If you find your memory failing, check the levels of vitamin B1, vitamin B12 and thyroid hormone in your blood.
Deficiency of any of these can impair your memory. While epilepsy, stroke and other brain conditions can affect memory, these are generally not the main causes of memory impairment. More common conditions such as high blood pressure and diabetes have an important impact on cognitive function.
A study published in March in the Neurology journal which studied 1,400 elderly individuals reported that those who developed diabetes or high blood pressure in middle age were more likely to develop memory impairment.
The presence of diabetes may cause the brain to shrink over time, especially the hippocampus, the memory centre.
Diabetes and high blood pressure also increase the risk of damage to the microvasculature of the brain, identifiable through a magnetic resonance imaging (MRI) of the brain as bright white spots called white matter hyperintensities (WMH).
The presence of extensive WMH is a predictor of future stroke and dementia. Studies on dementia and high blood pressure, such as the Progress trial, show that active treatment of blood pressure, especially in stroke patients, can reduce dementia.
Multiple studies have also shown that 70-year-olds with a lower systolic blood pressure were less likely to develop dementia, and that those with significant WMH in the brain are most likely to show significant progression of brain ageing. Lowering the blood pressure is thus effective in preventing progression.
Do take note that the greatest benefit of preventing the development of WMH in those with high blood pressure and diabetes is seen from good control from middle age. Hence, as the saying goes, prevention is better than cure.
Last but not least, one of the increasingly common causes of WMH and hence, memory impairment, is the decrease in oxygen to the brain during sleep, a condition commonly termed as obstructive sleep apnoea.
It is often due to obstruction in the nose and/or the palate falling backwards as the throat muscles relax during sleep, resulting in the obstruction of the airway at the back of the throat.
Over a long period, chronic nocturnal oxygen deprivation has been shown to shrink the brain and cause WHM. If this is unresolved, dementia may ensue.
Hence, if you always feel tired despite having sufficient sleep, snore nightly, constantly breathe through your mouth during sleep or have dry throat when you wake up, see your physician about the likelihood of airway obstruction. Ensuring that you get adequate oxygen when you sleep will not only prevent progression of brain ageing, but has been shown to improve memory and brain volume in those with chronic nocturnal oxygen deprivation in the brain.
Forgetfulness is not a foregone conclusion or a natural part of ageing. Taking proactive measures to keep good health when you are still young can yield significant benefits, including memory preservation as you age.
- Dr Lim is the medical director at the Singapore Heart, Stroke & Cancer Centre. He is also editor-in-chief, Heart Asia, a journal of the British Medical Journal Publishing Group; he chairs the scientific advisory board of Asia-Pacific Heart Association and is an honorary professor and senior medical adviser at the Peking University Heart Centre
- To read more of Dr Lim's previous health-related articles, please visit: http://www.btinvest.com.sg/specials/shscc
This series is brought to you by Heart, Stroke and Cancer Centre. It is produced on alternate Saturdays.