The winter death rate among older people in Wales rose in 2007-08
People are being urged to check on elderly relatives and neighbours as temperatures plunge across Wales.
Deputy Chief Medical Officer for Wales, Dr Jane Wilkinson, said the cold weather could have a "major impact on people's health and well-being".
"I would encourage people to check to see if elderly relatives and neighbours are managing when the weather is very cold," she said.
Temperatures as low as -10C have been recorded in Wales during the cold snap.
The Welsh Assembly Government's annual Keep Well This Winter campaign aims to remind older people and those with chronic conditions how they can stay safe and well.
"The campaign highlights the importance of wearing several layers of clothing, having regular hot meals and drinks, and the need to keep at least one room in the house warm," said Dr Wilkinson.
She said the cold weather could aggravate conditions such as asthma, and encouraged friends and neighbours to keep an eye on older people.
Age Concern runs good neighbour schemes which offer support to older people in their own homes.
This can involve help with shopping and transport, benefits advice or just popping round for a chat.
Kathryn Coupland, a scheme co-ordinator in the Llantwit Major area in the Vale of Glamorgan, said her volunteers would be keeping a close eye on older people during the cold spell.
"Some people like somebody to come and visit them for a chat and a cup of tea so I have volunteers who do that," she said.
"Sometimes we take them shopping and other times they're not able to, so our volunteers do the shopping for them, which might be an issue in the cold weather.
"I know the volunteers who regularly pay home visits will be keeping an eye on our clients. Volunteers will tell me if they're worried about anyone."
TIPS TO KEEP WARM AND WELL
Heat your home well
Dress well for warmth
Get financial support
Get a flu jab
Source: Keep Well This Winter campaign
Ms Coupland said she was getting bread for one woman before Christmas and realised she was not well.
"I contacted her doctor when I could see she wasn't well. She had a cold or flu or this virus and she was admitted to hospital," she said.
The winter death rate among elderly people in Wales went up in 2007-08 to 1,400, which was 100 more than the previous year.
There is concern from charities that the figures for what is officially known as "excess winter deaths" will be even higher this year because of the cold spell.
"Our concern is that cold-related illnesses, heart attacks, strokes and other ailments will increase because of the cold weather with, potentially, fatalities," said Iwan Rhys Roberts, of Help the Aged in Wales.
"We cannot overestimate the importance of keeping your house warm, eating warm meals and drinking warm drinks and wearing layers during a cold spell.
"It's also important that we show community spirit and we look out for older people especially now when the weather is particularly cold."