Understanding Dementia – Are Women Really At Higher Risk

As we get older, our memory tends to age with us. Recollection of names or words can slow, and it might be harder to learn new information. Though it may be frustrating, these minor memory quirks are considered a normal part of aging. But what about the not-so-normal aspects of memory loss? When does forgetfulness move from an age-related side-effect to something more serious like dementia? And are women really at higher risk?

The Dementia Umbrella

Dementia is not a disease but the name given to a group of symptoms affecting memory, reasoning, and decision-making. Dementia is progressive in nature – this means that symptoms are generally mild at first but will worsen over time. “We describe dementia as an umbrella,” says Dr Brigid Ryan, a neuroscientist and research fellow with the Centre for Brain Research at the University of Auckland, “a group of symptoms that affect thinking and behaviour but can be caused by lots of different diseases – and the most common cause is Alzheimer’s.” 

Alzheimer’s disease accounts for around 60-70% of all dementia cases. It is thought to be caused by an abnormal build-up of protein ‘plaques’ and ‘tangles’ within the brain and brain cells. These plaques and tangles disrupt regular brain cell activity, usually beginning in the area of the brain that controls memory. Another relatively common type of dementia, is vascular dementia. “We think that it affects around 15 to 20% of all people with dementia,” says Brigid, “[and is] caused by damage to the blood vessels in the brain. This sometimes happens when people have a stroke, for example.” 

Less common types of dementia include Lewy body dementia and frontotemporal dementia. Lewy body dementia accounts for roughly 5-10% of all dementia cases. It is caused by abnormal deposits of a specific protein in the brain. These deposits, referred to as Lewy bodies, interfere with cell function in the brain – eventually leading to dementia. Frontotemporal dementia is caused by the degeneration of nerve cells in the frontal and temporal lobes of the brain. Frontotemporal dementia is unusual in that it tends to present in people under the age of 65. “Of all the people in New Zealand with dementia,” says Brigid, “about 7% of them will be under 65. That translates to about 4000 people.”

Normal Aging or a Cause for Concern

The signs and symptoms of dementia differ depending on the cause. In Alzheimer’s disease, the main symptom is generally memory loss. Memory loss can present as difficulty remembering conversations, repeated statements or questions, misplacing possessions, or getting lost in familiar environments. In advanced Alzheimer’s, people can forget how to perform basic activities, such as dressing or preparing food. Lewy body dementia presents in a similar way to Alzheimer’s disease. “But,” adds Brigid, “it also has an additional component of movement. So, people will have similar movement changes to someone with Parkinson’s [disease] – things like muscle stiffness and tremor.” 

Dementia affects people differently. Some people may find it difficult to communicate or control their emotions, while others may experience confusion or personality changes. Additional symptoms associated with dementia include difficulty planning, agitation, hallucinations, and unusual or inappropriate behavior. When it comes to sorting dementia symptoms from age-related memory changes, Brigid emphasises the importance of impact. “ . . .the really critical thing,” explains Brigid, “is that the change needs to be significant enough that its affecting your normal functioning.” 

One of the difficulties in recognising dementia is that the affected person often lacks the insight to notice symptoms. “Quite often it will be someone close to the person who notices changes,” says Brigid, “whereas the person with dementia actually thinks everything is fine. So, something that I often hear people saying is that if you think there’s a problem, you’re probably fine. But if your partner thinks there’s a problem, then you should probably take it seriously.”

Recognising Risk

Studies have identified a number of environmental, lifestyle, and genetic risk factors for dementia. Aging is the single biggest risk factor because it increases the likelihood of health conditions that can damage the brain causing dementia, such as a stroke. From 65 years of age, the risk of dementia roughly doubles every five years. “So, if you’re between 65 and 69,” says Brigid, “about 2% of people in that group have dementia. But between 85 and 89, it’s about 20%.” In people over 90 years old, this figure rises to around 33%. 

When it comes to genetics, scientists have identified ‘risk’ genes and ‘causative’ genes as having a role in the development of dementia. Having a risk gene does not mean a person will get dementia, and, in most cases, the increased risk is only slightly higher than someone who does not carry the gene. Causative genes are different from risk genes. They contain a genetic mutation that will cause dementia in those who carry them. “Less than 1% of people with Alzheimer’s will be born with a single genetic mutation that will directly cause their Alzheimer’s,” says Brigid, “with frontotemporal dementia, it’s more like a third of people that have that genetic cause.”

Hearing loss is another somewhat surprising risk factor for dementia. In one of the first studies to explore this relationship, mild hearing loss was found to almost double the risk of dementia, while moderate hearing loss was found to triple it. Severe hearing loss increased dementia risk by nearly five times that of people with normal hearing. Scientists believe hearing loss may increase dementia risk by accelerating brain atrophy (shrinking) and encouraging risk inducing behaviours such as withdrawing from social interactions.

Alcohol use is another avoidable risk factor to consider. “There is a specific type of dementia,” explains Brigid, “that’s caused by the overuse or misuse of alcohol. That occurs when someone is far exceeding the recommended amount of alcohol. It’s an interesting form of dementia because if it’s diagnosed early enough, it can actually be reversed – if the person stops drinking.”

Air pollution, a history of depression, and type 2 diabetes are other factors believed to increase the risk of dementia. “Another thing I wanted to mention,” adds Brigid, “[is that] there is no evidence that any dietary supplements are useful to prevent or cure dementia. I think it’s important to be wary of anyone who is claiming they have a dietary supplement that [does] because currently, there aren’t any.” 

Women and Dementia

Over 55 million people worldwide are living with dementia. Yet, women are disproportionally affected, making up 65% of all dementia cases – and dementia-related deaths. The main reason for this difference is thought to be because women tend to live longer than men – and dementia risk increases with age. But age alone doesn’t explain the dementia gap.

Recently, however, researchers have begun to explore if estrogen plays a role in the development of dementia. While this research is still in its infancy, studies have shown that women frequently report negative cognitive changes during menopause transition. There is also evidence to suggest that early menopause and shorter reproductive periods may increase the risk of developing dementia.  “[Estrogen] does seem to have a role in the brain,” says Brigid, “and there’s evidence that it might be involved in memory and other types of thinking abilities . . . there’s a hypothesis that maybe because postmenopausal women have less estrogen, and if their estrogen is important for memory, then maybe it’s increasing [the] risk of dementia. But basically, we don’t have enough evidence yet to say either way.”

Unsurprisingly, the potential relationship between estrogen and dementia has given way to studies exploring hormone replacement therapy (HRT) as a possible preventative. The results, however, are mixed. While some studies show a positive effect of HRT in reducing dementia risk, others show a negative effect – or no effect at all. While these results might seem disheartening, it’s a positive step forward. “It’s encouraging this area [of research] is being looked into more,” says Brigid, “it could potentially tell us something about the origins of dementia . . . and if something like estrogen was involved in that, it would also potentially be a target for treatments – which would be really exciting.”