Nadja Swarovski, 46, and her husband Rupert Adams, 48, talk about the impact of Alzheimer's on their family. Nadja is the only woman on the executive board of the Swarovski Crystal Business, founded by her great-greatgrandfather, and also chair of the Swarovski Foundation. Rupert, 48, is a partner in an investment group. They live in London with three children aged 12, 11 and 10.

Nadja says: The first time Rupert introduced me to his mother Pauline she was nice, but very quiet. I had just moved to London from New York and her manner was such a contrast to what I'd been used to. In New York, everything is fast-paced, everyone is loud and noisy! Rupert's father had died suddenly at he age of 57 and Pauline lived alone.

She was becoming a little bit vague and forgetful. She'd forget names, her keys and say things that showed her understanding of the world was slowing down. For a while it was easy to overlook because of Pauline's nature.

In 2002, when Rupert and I were getting married, Pauline asked my father, "Who is going to walk Nadja up the aisle?" It was another sign that something was wrong - and soon after, Rupert and his sister took Pauline to the well-known neurologist Dr Angus Kennedy. A brain scan showed early-stage Alzheimer's. She was 62.

It's hard to plan ahead or make concrete decisions because the disease is so "inconcrete". Pauline started on Aricept medication, which slows the progression in some people, and we were told the life expectancy was 8-15 years. That was 15 years ago. Her deterioration has been a gradual retreat into her own little world. There are stages along the way. At first, she was still driving but that had to stop because she'd forget where she was going. Then she'd need help getting dressed, or bathing.

In some ways, it has been easy for the family to care for her because she is still so kind and gentle. Alzheimer's took away the cognitive thinking and you're left with the soul. Even as the disease progressed, Pauline would join us at meals and though she couldn't contribute on an intellectual level, she always felt the emotion of what we were talking about. So she'd either be laughing along with us or sympathising. If one of us was sad, she'd notice. She'd say, "Oh gosh. Oh dear."

Now Pauline lives in a cottage close to Rupert's sister, with 24/7 care. Pauline can't talk at all now, she's bedridden, but she'll always receive you with a smile.

Rupert and his siblings are thinking about taking the test to see if they have a gene defect that increases the likelihood of developing the disease. I really believe that the more we talk about this disease, the more awareness there is, the closer we'll get to solving it.

Rupert says: My mother was an amazing woman - caring, gentle and kind. In 1997, my father died suddenly of heart failure. I firmly believe that the shock triggered something in my mother that may have been dormant.

She was asked to be Lady in Waiting to the Queen, which was a tremendous honour. She filled this role for five years, but her creeping symptoms of what we now know was Alzheimer's made it more and more difficult.

I'm very close to my siblings, we've shared different responsibilities. Whether or not to get tested for the gene defect is a tough one. Our children have dealt with it pretty well.

Now, Mum may not know who we are but the emotional connection survives. You can hold her hand, talk to her and just feel that connection making her happier.

What is the genetic link with Alzheimer's?

Inheriting dementia is very rare. Less than one per cent of people living with Alzheimer's disease, the most common type of dementia, may pass on the condition to their children and grandchildren. In cases where this does happen, symptoms often start at a much younger age than usual (so-called young-onset Alzheimer's disease). Defects in three genes, APP , PSEN-1 and PSEN-2, are known to cause this inherited form of Alzheimer's.

Defects in these genes can now be picked up by a fairly simple test based on a blood sample. If a defect is found in a person diagnosed with young-onset Alzheimer's, this warrants testing their adult birth relatives for the same mutation. This is called "predictive" testing because finding the gene defect in a healthy person predicts, with near certainty, if they will go on to develop Alzheimer's.

Genetic testing is available on the NHS for affected families and is carried out in a special regional genetics centre. Deciding to have a predictive test or not can be very stressful, so support and counselling is important for those undergoing it.

When are memory problems a sign of dementia?

Forgetting why you have walked into a room. Not necessarily a sign of dementia and can happen to anyone, particularly 50s-plus. A possible sign of dementia is if the room itself seems unfamiliar, even when it's a room they know well.

Occasionally forgetting the name of a person, thing or place. This is very common. It may only point to dementia if you forget close friends, places that are very familiar or forget things very frequently.

Forgetting where you have left your car keys. This isn't something to worry about. What is a concern is leaving something in an unusual place - for example your keys in a bathroom cabinet.

"Creating a plan for my future has been incredibly empowering"
Kay Sayer, 70, lives with her husband, Ian, in Christcurch. She has two grown-up sons from an earlier relationship. Kay was diagnosed with Alzheimer's disease in 2014.

Kay says: Before I received my diagnosis, I spent a lot of time hoping I didn't have dementia. My mother had Alzheimer's and her mother had vascular dementia, so when I started forgetting things - whether I'd done a chore or what I'd done five minutes earlier - I knew I couldn't just bury my head in the sand.

It took 18 months to get a proper diagnosis - it's hard not to feel frustrated by that, even now. On my first visit to the doctor, he simply asked a few questions - who the Prime Minister was and what day it was - which inevitably I got right, and initially I was told that I had mild cognitive impairment. I was asked to wait another six to eight months, by which time I had no doubt I was in the early stages of the disease. Eventually, an MRI revealed I was right.

My dad kept my mum's diagnosis a secret from me for many years - I've made a point of being open with my family; I want us all to be as informed as possible - and the boys and Ian treat me as if I'm normal, which I am...apart from my brain!

Early on, I gave Ian the power of attorney and I told everyone what I wanted to happen when I'm about to die. It might sound morbid, but actually, it's empowering. You lose so much control when you have dementia, so it's nice to be able to claw some back. There are still decisions we haven't made - I'd rather not go into a care home, but I suspect I might have to.

I'm still in the early stages of the disease, but my biggest struggle is remembering names and numbers. And sometimes, I can't find the words at all. I have to say to people, "Please can you be patient?" because I want to finish a sentence on my own. I write my daily schedule in a diary, otherwise I wouldn't remember what I was doing either.

You never lose hope of a cure - you can't. I've been on Aricept since my diagnosis, but unfortunately it's tends to only be effective for about five years. So I also take part in drug trials at Moorgreen Hospital - the first one I did meant injecting myself with a drug once a day for a year, and I'm about to start another, which is a daily tablet. I know that they won't necessarily help me, but they might help somebody else further down the line.

I haven't let dementia stop me doing things. I go orienteering and I've joined a local singing group. Unfortunately for me, it's my brain that's gone wrong, but the rest of me is okay, so why not make the most of that?

One thing I know is that I couldn't do get through each day without Ian. He's so patient. My diagnosis has actually brought us closer.

Ian says: When Kay was diagnosed, it might sound strange, but part of me felt relieved. It was distressing, of course, but I'd noticed her memory had been getting worse - she'd ask the same thing two or three times within few hours - and to have someone say, "This is what's wrong" at least meant we could try to do something about it.

You meet some people and they'll whisper, "My wife's got Alzheimer's" - but we don't try to sweep it under the carpet. Why should you feel embarrassed about a disease? When you're open about it, it destroys any awkwardness when Kay stops halfway through a sentence because she's forgotten the next word. There's no, "Oh, what's wrong with her?"

Kay is still very independent - she drives, cooks and does the shopping - but the disease is always in the back of my mind. I purposely don't do things with her that I think she could do on her own, but gradually we're having to make changes. She's got lost a couple of times when we've gone orienteering, which was frightening - so now we insist she takes her phone with her as a safety net.

Our motto is "carpe diem" - seize the day - we're doing everything we can, while we can. Kay has never been up Mount Snowdon, so we've got that scheduled for July.

We try not to dwell on what's to come, but I'll care for Kay full-time when she needs it. It's not a decision I've actively made, it's just what I feel will be right. We're as close now as we've ever been - a disease isn't going to change that.