The study found that women with Alzheimer’s had significantly fewer of these unsaturated fats in their bloodstreams, but “there was no difference in these lipids in healthy and cognitively-impaired men,” Legido-Quigley says.

These findings suggest that there is “something going wrong in the brains of women” who develop Alzheimer’s disease which is not affecting men. Scientists don’t yet fully understand what that process is, but the finding was “a big surprise for us, because we’ve been doing this work for 15 years and I’ve always assumed that there would be a mixture of sexes within results like this,” Legido-Quigley says.

Proving that the disease is directly caused by a decline in fatty acids is complex, but Legido-Quigley now believes that women “should take extra care to make sure that they are getting omega-3 fatty acids in their diet” through food or supplements in order to protect themselves from Alzheimer’s.

But it’s clearly not the only factor at play when it comes to our risks of Alzheimer’s. Exactly how large a role a woman’s biology plays in their heightened risk of the disease, versus social ones, “is the billion-dollar question,” says Barbara Sahakian, professor of clinical neuropsychology at the University of Cambridge.

So what can you do to reduce your likelihood of getting Alzheimer’s disease if you’re a woman? This is what we know so far.

1. Build up your cognitive reserve at any age

Numerous studies have shown that building up “cognitive reserve” – your brain’s ability to withstand ageing and disease – throughout your life, by challenging your brain in new and inventive ways, is a good way to reduce your likelihood of developing dementia.

This reservoir of memories and skills is built up through life experiences of all kinds, such as working, studying for a degree, learning a language and socialising. A review published earlier this year found that people who develop Alzheimer’s disease, despite having a large cognitive reserve, also maintain their cognitive function for longer than those who start out with less.

“Historically, women have had less access to intellectually-demanding jobs,” says Professor Barbara Sahakian, a professor of clinical neuropsychology at the University of Cambridge. “Caring for children is certainly stimulating, but it’s not the same as solving problems and engaging with other adults in the workplace. So it may be the case that women who are in their eighties and developing Alzheimer’s today have had fewer chances to build up cognitive reserve.”

If you’re a midlife woman reading this, then chances are you’ve likely spent longer in employment than a woman in your mother’s generation, so your risk of developing Alzheimer’s disease may already be lower than it would have been 50 years ago. But it is still worth working to boost your cognitive reserve for the long-term protection it can bring, and doing so can have a positive impact at any age, even if you’ve had long stretches out of work or have never worked full-time.

“You need to keep your brain active – it’s a use it or lose it thing,” says Prof Sahakian. It is especially important to look after your hippocampus, which deals with episodic memory – “of where you’ve parked your car or left your keys” – and your entorhinal cortex, which deals with memory consolidation, as these are the parts of the brain most vulnerable to dementia-related decline.

“The really key part is variety,” Sahakian says: alternate learning a language with a physical skill like painting, and then try volunteering somewhere new to meet a wider range of people.

2. Look after your mental health

“Women experience more depression than men,” says Sahakian, a split that still exists in midlife and afterwards. At 60, the incidence of depression sits at 28% for women and 22% for men. Experiencing depression or anxiety at any point, “even in early adulthood”, can increase a person’s chance of developing dementia, but suffering from depression that begins after someone turns 75 “is very strongly associated with dementia,” Sahakian says.

The best course of action if you have depression is to seek treatment, be it through SSRIs, psychotherapy or a mix of the two. There is no age at which it becomes impossible to cure depression. The best place to start with finding help is with a visit to your GP.

Women may also be more affected by social isolation as they age, and being socially isolated can increase Alzheimer’s risk “by as much as 26%,” Sahakian says. To remedy that, start with small steps: strike up a conversation with the cashier in your corner shop, or go out for a stroll with your neighbour. Face-to-face conversation is best as it demands the most of your brain, “but electronic communication, on the phone or a video call, is certainly much better than nothing,” Sahakian says.

3. Consider taking HRT

How menopause affects the brain and puts it at risk of Alzheimer’s “is something that needs much more research,” says Sahakian. Scientists around the world are now working to establish a link between the two, which is likely to be very significant, as lipids such as omega-3s make up 60% of our brains and are influenced hugely by the hormone changes that cause the menopause.

“The lipid [fat] makeup in the brains of women and men is different, and it changes a lot in women in the menopause,” says Legido-Quigley. These changes happen because of declining estrogen levels, which causes other kinds of lipids in the brain to rebalance themselves in different quantities.

“The way we store lipids changes very quickly as well, after the menopause,” she adds. Exactly what that means for brain health is not yet clear.

We all know, however, that the menopause can be stressful for the majority of women, and that a stressful life means a higher risk of Alzheimer’s in older age. Hormone replacement therapy (HRT) “isn’t currently recommended as being neuroprotective in its own right,” Sahakian says, but if you’re really suffering with menopause symptoms, especially depression that can be caused by its turbulence, then it may well be worth having a conversation about HRT with your doctor.

4. Make sure you exercise – even brisk walking helps

Exercise “is extremely important when it comes to preventing Alzheimer’s,” says Sahakian, who has written a book, Brain Boost: Healthy Habits for a Happier Life, in part to make that point. “It boosts your mood, improves cognition and improves your immune system, too. You really must make sure that you get sufficient exercise, but women are less likely than men to do so.”

Research suggests that people who exercise regularly are up to 20% less likely to develop dementia than those who do not, and the protection offered by regular movement may be even more important for women. One study, published in 2018, found that women who are very fit in midlife are a full 90% less likely to develop dementia than women who are only moderately fit – and in the unlikely event that they still wound up with the disease, it happened 11 years later, at an average age of 90, compared with 79.

The Alzheimer’s Research and Prevention Foundation recommends that everyone carries out at least 150 minutes of exercise each week, which can be a combination of cardiovascular exercise and strength-based exercise. Brisk walking even counts, or walking at a pace that leaves you able to chat but unable to sing. So does swimming and (effortful) cycling.

5. Eat more eggs, as well as oily fish

The latest research from King’s College London suggests that diet is especially important for women when it comes to preventing Alzheimer’s. Specifically, getting enough omega-3s in your diet, either through foods such as oily fish like salmon or mackerel – two portions of which per week is recommended – or through omega-3 supplements.

In theory, “both are as good as each other,” says Legido-Quigley, but if you’re going down the supplement route, be sure to read the label on the back of your packet. “Some supplements only contain one kind of omega-3, called DHA, but you need both. EPA seems to be the fatty acid that is really key in reducing your risk of dementia, but some supplements on the high street contain none of this at all,” she warns.

To boost your Alzheimer’s protection further, however, make eggs a staple in your diet. Eggs contain phosphocholine, which “helps the body to produce and use omega-3,” she adds.

Contrary to the belief that too many eggs can raise cholesterol and cause health issues down the line, Legido-Quigley believes that “women who are concerned about developing Alzheimer’s should absolutely get more eggs into their diets”. So if you’re worried about developing Alzheimer’s in later life, the best place to start may be with your weekly shop – just make sure that you’re careful about the kinds of supplement you pick up.