Other risk factors

This chapter is devoted to a selection of other topics which appear in the popular press from time to time. Some sections cover potential risk factors which an individual can do something about. Other sections are about drug treatments. In all of these cases, the evidence is inconclusive although further research may change that.

Aluminium and Alzheimer’s disease

Background
Aluminium is all around us in the environment. It is generally thought of as the light silvery metal used to make pots and pans. However, it also makes up eight per cent of the earth’s surface and is present in water and the air. Because it is so common it is very difficult to know how much of it you are taking in.

Researchers began exploring a possible link between aluminium and Alzheimer’s disease back in 1965 when it was found that injecting aluminium compounds into rabbits caused tangle-like formations in nerve cells. However, these tangles are different from the tangles found in the brains of people with Alzheimer’s disease.

Evidence
Much of the evidence linking aluminium to Alzheimer’s disease is circumstantial. Aluminium in large quantities is shown to have a toxic effect on the nervous system. It has also been shown to be associated with both the plaques and tangles in brains of people with Alzheimer’s disease, but this does not prove that it is a cause of Alzheimer’s disease.

None of the evidence so far has proved that aluminium contributes to the degenerative changes which cause Alzheimer’s disease. Based on current knowledge the majority medical and scientific opinion is that exposure to aluminium is not a significant risk factor. Most older people do not get Alzheimer’s disease despite the widespread presence of aluminium in the environment.

Guidance
Although aluminium is ever-present, very little is actually absorbed by the human body in normal day-to-day life. Some people worry about using aluminium pans. Most food takes in almost no aluminium, but acidic foods such as rhubarb can absorb it, unless the pan is coated, non-stick or hard anodised aluminium. Some people choose not to use aluminium plans to cook acidic food, but there is no evidence at the moment to say whether this makes any difference to the risk of getting Alzheimer’s disease.

Ginkgo biloba and dementia

Background
Ginkgo biloba comes from the dried leaves of the maidenhair tree. It is an antioxidant that is believed to have medicinal purposes, particularly for enhancing memory and aiding circulation. It is widely available over the counter in pharmacies and health food shops.

There is interest in ginkgo because it is thought to improve the blood flow to the brain, for its possible benefits for memory improvement and for its antioxidant properties.

Evidence
A review of existing evidence on the benefits of ginkgo for cognitive impairment and dementia took place in 2002(86). It found that ginkgo appeared to be safe, with no more side effects for those who used it in the studies than for those who were given a placebo (dummy pill) instead. Overall there was promising evidence of the benefits of ginkgo for cognition and brain function. However, there was some inconsistency in the results of different studies and dissatisfaction with the methods used in many of the studies.

Guidance
More research is necessary to identify any benefits that ginkgo may have in helping prevent or slow the progress of dementia. There is some concern that ginkgo may have side effects when taken with some other medications or when there is a pre-existing medical condition. It would therefore be advisable for anyone considering taking ginkgo to consult their GP if they are on an ongoing course of treatment. It is also important to be aware that the quality of ginkgo products on sale varies.

Head injury and dementia

Background
Head injury, particularly more severe or repeated injury, is regarded as a risk factor in the development of Alzheimer’s disease and other forms of dementia later on in a person’s life. It is thought that deposits may form in the brain as a result of head injury and this may increase the risk of dementia. Boxing has been associated with a dementia called ‘punch drunk syndrome’ and the heading of old style leather footballs was considered a risk factor for brain damage.

Evidence
A study of World War II servicemen who had suffered head injury in early adulthood found that moderate to severe injury increased the likelihood of developing Alzheimer’s disease and other types of dementia later on(87). Most studies have continued to find a link between head injury and increased risk of dementia. However, the findings of these studies have been varied and therefore do not come together to provide a clear picture of the risks(88).

Guidance
Not everyone with a head injury goes onto develop dementia. However, taking steps to avoid head injury is advisable, such as wearing a seatbelt when travelling in a vehicle, keeping to the speed limit and using protective head gear when riding and playing sports.

Hormone replacement therapy and dementia

Background
Hormone replacement therapy (HRT) provides extra oestrogen to top up a woman’s natural supply, which diminishes with age. HRT is used to relieve unpleasant symptoms associated with the menopause, such as hot flushes and excessive sweating.

Observational studies have suggested that women using HRT have a reduced risk of developing dementia and it has also been proposed as a possible treatment for women who have dementia.

It is thought that HRT may help by reducing the amount of a protein called beta amyloid. Beta amyloid contributes to deposits called plaques which form on the brain of someone with dementia. Another possibility is that HRT may help the brain cope with illness and also top up neurotransmitters damaged in dementia.

Evidence
There have been mixed results from research. Whilst some studies have suggested that post-menopausal HRT improves cognitive performance and may help to prevent or slow the progression of dementia, it is thought that lifestyle differences between those who use HRT and those who do not may mean that these findings are not accurate(89). Other studies have not found that HRT either reduces the risk of developing dementia or slows the progression of the disease(90)(91)(92). One study(93) suggested that women who start taking combined oestrogen and progestin past the age of 65 are more likely to suffer from mild and severe dementia. The study found that combination hormone therapy doubled the risk for probable dementia in women aged 65 and older and did not prevent mild cognitive impairment. Further study is required to establish the potential role that HRT may have in challenging the illness.

Guidance
Based on existing evidence, HRT should not be taken solely for any benefit it may have for the brain. HRT has been associated with a small but increased risk of stroke and the development of some cancers(94).

Scottish guidelines for the management of patients with dementia do not recommend oestrogen for the treatment of associated symptoms in women with dementia(95). Whilst women who are taking HRT may be enjoying possible additional benefits, women who are not experiencing menopausal side effects should not take HRT unless clearer evidence is found to show that the benefits outweigh the risks.

Non steroid anti inflammatory drugs (NSAIDs) and dementia

BackgroundNSAIDs are a group of drugs used to relieve pain and to treat inflammatory conditions such as rheumatoid arthritis and osteoarthritis. They include aspirin, ibuprofen, piroxicam and diclofenac.

It is thought that NSAIDs may reduce the risk of developing dementia for two reasons. Firstly, aspirin has been shown to reduce vascular disease by thinning the blood and reducing the risk of clots, thus reducing the risk of heart attack and stroke, which both increase the risk of dementia. Secondly, it is thought that NSAIDs may alter the processing of the amyloid protein in the brain, which is believed to be one of the key factors in the development of Alzheimer’s disease.

Evidence
A number of studies have found that people who develop dementia typically have a lower use of NSAIDs(96). There is also some evidence that the long term use of NSAIDs may provide protection against Alzheimer’s disease(97). However, it is not known whether the drugs reduce the risk or if there is some reason why people with chronic pain are less susceptible to Alzheimer’s disease.

A review of whether ibuprofen is effective for the treatment of people with Alzheimer’s disease found that no robust scientific evidence exists at present(98). There is therefore a need for further research to develop a clear understanding of the impact that NSAIDs have on Alzheimer’s disease and other dementias.

Guidance
Based on current knowledge NSAIDs should not be taken to reduce the risk of developing Alzheimer’s disease and other types of dementia. NSAIDs are known to cause stomach irritation. There are also more serious side effects associated with prolonged use of these drugs, such as ulcers and gastrointestinal bleeding.

Statins and dementia

Background
Statins are a group of drugs prescribed to reduce cholesterol. They lower levels of LDL cholesterol, the type most strongly linked with coronary artery disease and stroke. They do this by blocking a liver enzyme essential for cholesterol production. There are a number of statins available such as Atorvastatin, Fluvastatin, Pravastatin, and Simvastatin

Statins help to keep the blood vessels and heart healthy. This may in turn reduce the risk of vascular dementia. Also high cholesterol levels may aid the production of beta amyloid protein, which is one of the chemicals though to cause damage to the brain in Alzheimer’s disease. These factors have led scientists to consider whether statins would lower the risk of developing dementia.

Evidence
Studies have found a possible link between statins and a reduced occurrence of Alzheimer’s disease(99). A review of evidence on the role of statins in reducing the risk of Alzheimer’s disease in 2001 concluded that existing studies were not conducted in the manner necessary to stand up to rigorous scientific testing(100). Two recent studies did not find a link between statins and a reduced risk of Alzheimer’s disease and other dementias(101)(102). There is a need for further research to establish if there is a link between statins and dementia risk.

Guidance
Based on current knowledge statins cannot be recommended to reduce the risk of developing Alzheimer’s disease or other forms of dementia. However, keeping cholesterol within recommended levels is good for general health. A diet that is low in saturated fat and regular physical activity are recommended for reducing cholesterol levels.

Other factors and dementia risk

A number of other things have been suggested as possibly having a beneficial effect in preventing or delaying the onset of dementia. However, often these are promoted in the media even though there is no research evidence to provide an understanding of their possible benefit or lack of it.

Alcohol
It is now generally thought that light to moderate alcohol consumption may have health benefits. A low level of alcohol keeps the blood less sticky and reduces the risk of clots forming. Red wine in particular is believed to be good for you when taken in moderation. It contains antioxidants that provide the body with a defence against damaging free radicals. However, too much alcohol can lead to alcohol related brain damage and severe loss of short-term memory.

The findings from a large study in Rotterdam suggested that light to moderate alcohol consumption is associated with a reduced risk of dementia in people aged 55 and over(103). A further study found that those who drank no alcohol and those who drank alcohol frequently in midlife were both twice as likely to have mild cognitive impairment in old age as those who drank alcohol infrequently. It also found that risk of developing dementia increased with rising alcohol consumption for those individuals who carried a particular protein in their body(104). There is insufficient evidence to promote alcohol to non-drinkers as a means of reducing dementia risk. However, there may be benefits for those who enjoy drinking alcohol in moderation. Recommended maximum weekly alcohol limits are 21 units for a man and 14 units for a woman. A unit of alcohol is a small glass of wine, half pint of beer/lager or a pub measure of spirits.

Black Tea and Green Tea
A recent laboratory study has suggested that black and green tea could help improve memory by inhibiting the development of key enzymes in the brain that are associated with the development of Alzheimer’s disease(105). Black tea was found to counteract two chemicals, whilst green tea counteracted three. The effects of green tea lasted for a week, whereas the black tea inhibiting properties lasted for one day. Black and green tea both come from the same plant. However, black tea is fermented and green tea is not.

As green tea is not fermented its chemical properties are not changed and its antioxidant properties remain intact. It is thought that these may provide protection against Alzheimer’s disease by decreasing the production of the beta-amyloid protein. Research on mice genetically engineered to develop symptoms similar to Alzheimer’s disease, showed that if they were injected with large quantities of a component of green tea, fewer beta-amyloid plaques formed in their brains. However, another part of the green tea is known to block the positive effects of this component(106). A study of approximately 1,000 Japanese adults aged 70 and over found that the more green tea they drank the lower their chances were of having cognitive impairment(107). However, this does not prove a cause and effect relationship, as there may be other lifestyle reasons why green-tea drinkers would have sharper mental function. More research is necessary; but in the meantime, there is no reason to change tea-drinking habits.

Curcumin
Curcumin is the main active ingredient in turmeric, which is a popular spice commonly used in curries. It contains both antioxidant and anti-inflammatory properties.

It has been suggested that curcumin may stop the abnormal build up of beta amyloid, which contributes to plaque deposits that form in the brain of someone with dementia. Researchers have been investigating this theory in order to identify whether curcumin could reduce the risk or slow the development of Alzheimer’s disease. Whilst there have been encouraging findings from research projects using mice it is too early to know whether curcumin will be effective in the fight against Alzheimer’s disease in people(108)(109).

References
Glossary
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Useful links:

Information about dementia
Aluminium and Alzheimer's disease
Anti-inflammatory drugs and Alzheimer's disease
Alcohol-related brain damage - Wernicke's encephalopathy and Korsakoff's psychosis