Preventing memory loss

THE next time you find yourself forgetful, do not pass it off as part of ageing. While it is commonly believed that memory loss is an inevitable consequence of ageing, medical research has provided physicians with evidence that this deterioration can be reduced - and even reversed - when appropriate measures are taken.

Blood pressure and cognitive decline

The development of high blood pressure (HBP) in mid-life appears to be an important risk factor for the development of dementia later in life. The presence of poorly controlled HBP is associated with cognitive decline. Multiple studies on blood pressure lowering in the middle-aged showed that it decreased the incidence of dementia.

In the well designed Syst-Eur trials, the results show that the treatment of 1,000 HBP patients for 5 years can prevent 20 cases of dementia. This benefit is also seen in those with prior strokes. The Perindopril Protection Against Recurrent Stroke Study (PROGRESS), showed that there was a reduction of incidents of dementia or cognitive decline when blood pressure was reduced. The benefits of blood pressure lowering were particularly seen in certain classes of blood pressure lowering drugs.

In a 2013 Neurology journal publication on the subsequent analysis of the Ginkgo Evaluation of Memory Study (GEMS) - a 6-year effort to determine if use of the herb ginkgo biloba reduced dementia risk - a study team led by researchers from John Hopkins found that people over the age of 75 with normal cognition, who used blood pressure drugs such as diuretics,

angiotensin-1 receptor blockers and angiotensin-converting enzyme inhibitors, showed a reduced risk of Alzheimer's dementia by at least

50 per cent. Beta blockers and calcium channel blockers did not show a link to reduced risk in this study. Hence, the selective choice of blood pressure drugs may provide incremental benefit for reduction of dementia risk.

Is a fast heart rate detrimental?

The question that is often asked is this: If the resting heart rate is high, is there a detrimental effect on health? In the Prevention Regimen for Effectively Avoiding Second Strokes (PRoFESS) study, those with prior stroke who had a higher heart rate of more than

67 beats per minute (bpm) had an accelerated decline in cognitive decline. The findings suggest that a low heart rate can reduce the size of the stroke rather than reducing the likelihood of a second stroke.

The data also suggests that high heart rate may be considered as a risk factor for cognitive decline and dementia. It has also been observed that patients with Alzheimer's dementia had a higher heart rate when compared with controls.

Sleep disturbances

Patients who snore or sleep with their mouths open are likely to have decreased oxygen saturation in their blood while they sleep, resulting in oxygen "starvation" of the brain during sleep. This is also termed as sleep apnoea, and can be diagnosed with a sleep test.

Chronic oxygen deprivation during sleep can result in reduction of brain volume and damage to the brain. This damage appears as white patches on a magnetic resonance scan of the brain and are referred to as white matter hyperintensities (WMH). Decrease in brain volume and progressive increase in WMH are associated with cognitive decline and dementia.

This oxygen deprivation is due to obstruction of the nasal passages or obstruction of the upper airway, and can be relieved by appropriate treatment. Studies have also shown that those with decreased brain volume and memory impairment who are given sufficient oxygen therapy continuously during sleep for 3 months have an increase in brain volume and improvement in cognitive testing. Taking proactive measures to diagnose the problem and to relieve the airway obstruction can help to reduce the likelihood of cognitive decline.

Sleep deprivation with few hours of sleep or an interrupted sleep pattern can cause memory decline. During sleep, the brain consolidates the memories so that it can be recalled. Without sufficient sleep, which means 7 hours or more for adults, the brain has difficulty absorbing and recalling new information. A 2016 study of young adults and teenagers showed that those with sleep deprivation were more likely to form false memories - that is, incorporating misleading post-event information into their responses during memory retrieval.

Strokes

Strokes can cause significant cognitive decline. Risk factors for stroke include HBP, diabetes mellitus, high cholesterol, and smoking. These risk factors are easily identified and can be treated to reduce the risk of stroke. However, less apparent and a relatively common cause of stroke in the elderly is the abnormal heart rhythm termed as atrial fibrillation (AF). It is estimated that for those aged 65 and above, about one in ten has AF. In AF, there is a "short circuit" of the electrical system in the upper heart chambers resulting, in a heart rate of about 400 bpm. This condition increases the risk of blood clot formation in the heart chamber. If a blood clot forms, it can potentially flow out of the heart into the brain circulation, blocking an artery and causing a stroke.

Alcohol

Alcohol interferes with receptors in the brain, making them produce steroids that interrupt the learning and memory-building process and hence affecting short-term memory. Alcohol bingeing can also cause alcohol blackouts. During alcohol blackouts, the brain is not able to create long-term memories, but short-term memories continue to function.

As such , the person can continue to socialise and participate in activities that they will not be able to remember. Typically, alcohol-related amnesia are primarily anterograde, which means that that excessive alcohol impairs the ability of the brain to form new memories while the person is intoxicated, but it does not erase memories prior to the alcohol binge. Studies seem to show that slow gradual heavy consumption over an evening does not cause blackouts. Blackouts occur as a result of alcohol bingeing causing rapid blood alcohol elevation, often in a setting of drinking on an empty stomach or while dehydrated.

Medical procedures

Some diagnostic procedures to check the heart (coronary) , neck (carotid) or brain (cerebral) arteries involve the insertion of a long plastic tubing (catheter) through the leg artery or wrist artery and manipulating the catheter into the target artery, after which contrast dye is injected and X-ray images of the arteries (angiograms) are obtained.

While manipulating the catheters in the arteries, there is always a risk that the catheter may scrape against the wall of the aorta or an artery and dislodge cholesterol deposits into the blood stream. If these dislodged cholesterol deposits travel into the brain arteries, they can result in a stroke.

Minor "silent" strokes from invasive procedures such as coronary angiography have been reported to occur in 5-22 per cent of patients undergoing the procedure in at least 7 prospective studies. These silent strokes can contribute to the development of dementia. Hence, whenever you are asked to undergo an invasive angiogram test that involves the insertion of a tube into arteries in the vicinity of the neck arteries, you should always discuss with your physician a safer, non-invasive alternative.

Age wisely

Cognitive decline is not an inevitable consequence of ageing. Multiple non-genetic factors contribute to the development of cognitive decline and dementia.

Early recognition of the risk factors or conditions that can predispose to the development of cognitive decline will enable one to take proactive measures to age wisely.

• This article is produced in collaboration with Royal Healthcare Heart, Stroke & Cancer Centre