The Childline founder, 77, told the Press Association: "People have memories of Christmases full of light, laughter, warmth and company.
"Now, to be on your own, bombarded with 'happy families' adverts, with a frozen ready meal for dinner, and no-one to talk to ... the comparisons are so harsh."
The grandmother-of-five points to her service the Silver Line, which gives over-55s a friendly voice around the clock and is inundated over the festive season.
Since its 2013 launch, it has answered more than 1.6 million calls, offering weekly telephone chats and a pen-pal style letters exchange.
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Around two-thirds of its calls come overnight and on weekends, when other services are closed.
Dame Esther said she was inspired to create the charity after writing about her own feelings of despair following the death of her husband.
The former TV presenter said: "I was greeted with such a huge response, putting something into words people feel reluctant to admit can open the floodgates.
"At 71, I was living on my own for the first time and hating it. Because whatever you did during the day you came home to an empty flat - sometimes cold, always dark, always bereft of anybody.
"I was used to shouting 'hello' as I walked through the door and someone shouting 'hello' back. Not anymore."
The track record of Childline paved the way, Dame Esther believes, as people now recognise picking up the telephone can save lives.
But the stiff upper lip attitude of older generations means they are often reluctant to ask for help.
She added: "They have so much pride, they hate complaining, the last thing they want to be is a burden.
"And the inescapable fact remains that older people don't have the same pull on our emotions, and I'm afraid generosity, that guide dogs or donkeys do."
And the former journalist added she was tired of negative portrayals of the "ageing society", saying those past the prime of youth still had lots to offer.
She said: "Someone called the demographic the Graph Of Doom. I beg your pardon, am I an example of the doom that faces our nation?
"I'm thrilled David Attenborough is the inspiration behind Britain's most popular TV programme, Debbie McGee is absolutely wonderful, and excuse me saying so, is anyone going to say the two people in Buckingham Palace are past their sell-by date?
"Absolutely not. So instead of talking about older people as bed-blockers, house-blockers and so on let's prize them."
Reflecting on Silver Line's work, Dame Esther finishes with story of a man in his late 60s who lost his wife and became profoundly depressed and housebound, before picking up the phone.
"They were both great ballroom dancers. And suddenly he's lost the love of his life and dancing partner," she said.
"But one of our volunteers convinced him to go back dancing after a while, and he slowly got his mojo back.
"Now he's teaching ballroom classes every weekend. That's what can happen if someone cares about you, takes time with you, and rebuilds your confidence."