They have been happily married for 37 years. In the past five years, however, a third party has intruded.

The hanger-on is, at his best, an inconvenience, and, at his worst, a monster. He sticks closer than a lover to Steven Lau, who had no choice but to take him along to the wedding lunch for the youngest of his three daughters, Jessica, at an upscale hotel in Sentosa.

On that hot November day, Steven, 63, rose to his feet, to give a speech to the 250 guests present.

He reached into his shirt pocket for the piece of paper, which he unfolded. His middle daughter, Valerie, 33, stood next to him.

For two hours the previous day, she had helped him craft the speech. Sometimes, he nitpicked at her word choice, but could not suggest alternatives. Certain words have become irretrievable from a mind that sometimes feels like chicken floss.

Sentences have a habit now of coiling inside his mind and refusing to come out. Or his mind may wander, his words following as it meanders.

"I just want to let you all know that I am Jessica's dad - just a friendly reminder," said Steven, to laughter and loud cheering. Some among the relatives and friends were aware that he has dementia.

Perhaps, it was also a reminder to himself, anchoring him to the occasion and his place in it.

Then he began reading out his speech, brushing Valerie's hand away lightly, a little annoyed, when she pointed to where he had stopped.

This is simple, he thought. I can read my own speech.

"People can change over time and marriage is not like courtship. Marriage requires a lot of lasting commitment and love from both parties," Steven addressed his youngest child.

Sitting on the stage beside her husband, Jessica, 28, listened, a lump forming in her throat.

She understood the weight of what he had just said because she has seen for herself the toll that dementia has exacted on her parents' marriage and her mother's struggle in wrestling the monster.

His memory is not the only thing that is being stolen from him. Where he once insisted on punctuality from his daughters, keeping time is now beyond him.

That morning, he woke up half an hour late, which meant the traditional ceremony of veiling the bride had to be delayed.

That hiccup aside, he was the consummate host, mingling with the guests with ease and flair.

Valerie recalled her own wedding in France two years ago when she walked down the stairs of the chateau. Her father was at the bottom waiting for her, and the expression on his face was one she would never forget.

"He looks sad, it is as if he is trying to permanently store the memory of that moment even as it is already slipping away," said Valerie, choking up as she recounted what happened.

Jessica, too, resolved to be married as soon as she could so her father would be at her wedding as they remembered him. It was a memory she wanted for herself, even if the tide was going out on his.

WHEN IT BECAME CLEAR SOMETHING WAS WRONG

Steven's father died when he was six. His mother raised him on her $600 salary as a clinic assistant and part-time midwife. She is 88 years old now and has also been battling dementia for the past two years.

An only child, Steven learnt how to fight to avoid being bullied. He was also good at school, graduating among the top students in his accountancy class at university.

He had a short stint as an auditor, and in the late 1980s joined Sembawang Maritime as its chief accountant. In time, he moved on to business development in mergers and acquisitions.

Eventually he became a stockbroker, staying in that line for two decades, at first with securities firm Lum Chang Securities and then DBS Vickers.

"For stockbroking, you don't really need the know-how. You just need to 'know who'," Steven joked.

He worked hard, had a network of banker friends who trusted him with their trades, and worked almost round the clock daily. He would work till 11pm and then wake at 4am or 5am the next morning to track the US market.

At the peak of his career from 2005 to 2010, he earned up to $200,000 a month.

Wong Lai Quen, his wife, also did well in her career, having worked for a multinational IT company as a partner for 37 years before she received a golden handshake at the retirement age of 60 in 2018.

She travelled frequently for work and lived in countries such as China and Indonesia, spending years at a time apart from their children.

One of the first instances she noticed something amiss with Steven was when he visited her in China in 2013. She asked him to go to the post office to pay some bills but he forgot to do so.

His daughters recalled other warning signs - dad ringing them, wanting to know his own postal code, or asking the same questions at dinner over and over.

But the most worrying was when Lai Quen noticed he was failing to complete certain "buy" and "sell" stock market transactions for clients.

When the lapses were discovered, Steven had to reimburse the losses out of his own pocket.

Lai Quen knew the danger of making such mistakes in a high-pressure, time-sensitive industry and urged Steven to retire.

He was reluctant. He was a top performer who had won awards. Work gave him a deep sense of identity and fulfilment, and his relationship with clients went back so far that they were inclined to forgive his slip-ups. But when he saw how much money he had been coughing up - his blunder in one transaction cost him $50,000 - he knew he had to call it a day.

He retired from the brokerage firm in 2012. Then, the couple had not yet suspected that it might be dementia.

Said Steven: "I didn't feel good about leaving. But I couldn't be in denial and had to find out what was wrong with me."

YOUNG-ONSET DEMENTIA

Steven was just 58 years old when he was diagnosed with dementia.

People with young-onset dementia have it much harder because others do not treat their erratic behaviour with much empathy, given the syndrome's invisibility.

After he stepped down from work at 2012, he joined Lai Quen in China where she was based.

When the Laus moved back to Singapore in 2014, they immediately arranged to see a neurologist as they had been noticing more memory lapses and behavioural changes in Steven during their time overseas.

The specialist at Mount Elizabeth Medical Centre administered the mini mental state examination, a standard cognitive test. The questions tested his memory, mathematics and motor coordination skills.

For instance, he was asked to count backward from 100 at intervals of seven, as well as fold a piece of paper into half and put it on the floor beside him.

When the diagnosis of mild dementia came, Steven was so taken aback that he could only nod.

Though not surprised, Lai Quen began asking questions: Why did this happen to her husband when he was only 58? Did the fact that both his mother and maternal grandmother also suffered from dementia have anything to do with it?

In Singapore, one in 10 people aged above 60 lives with dementia, and half of those above 85 have the condition. It is estimated that by 2030, there will be more than 100,000 people with dementia, up from 82,000 in 2018.

Dementia is a term that describes a number of different conditions affecting the brain, all of which can rob patients of their memory and daily functions, such as thought processing, concentration and judgment.

It is a degenerative and incurable disease and people live with it about eight to 10 years on average, though some last for 20 years.

There is little treatment for dementia, but Steven receives a patch that is put on his back daily. It contains medication that aims to restore the balance of neurotransmitters in his brain, to improve his memory, awareness and his ability to perform daily functions.

Steven seemed to accept his condition, but there were signs that he may not be fully comfortable with being identified with it.

His daughters, for example, do not tell others in his presence that he has dementia, as he can be sensitive about it.

He quickly turned conversations about his condition to friends in a more advanced stage of the disease.

Struggling to find information after Steven was diagnosed, Lai Quen, 62, began reading widely.

To keep Steven mentally and physically active, they attend the Alzheimer's Disease Association memory cafe programme every Saturday. There, participants with dementia interact with others through activities. Some weeks, they sing, others, they play mahjong or musical instruments.

Steven also has twice yearly check-ups at the National Neuroscience Institute (NNI). As of February, his stage of dementia has still been classified as mild.

Specifically, he has vascular dementia, a type of dementia caused by reduced blood flow to the brain, and Alzheimer's disease, another type of dementia which is a progressive disease of the brain that slowly causes impairment in memory and cognitive function.

What had been hard for Lai Quen was finding herself alienated instead of supported when she told other people about Steven's condition.

"When I tell them that my husband has dementia, they will say, 'aiya, my mother or grandmother also has it'," she said. "And when I ask them how old their mother is, they say 80 or 90. I feel they couldn't understand my pain, Steven was just 58 when he got it."

An estimated 4,000 people in Singapore have young-onset dementia, which is defined as someone aged 65 and below who is diagnosed. Many are still working and have young families when the disease sets in, the NNI found in 2016.

For Lai Quen, it was that sense of estrangement that propelled her to be open with others about her husband's condition through advocacy.

"It is only by sharing about it more with others that people can help me."