Failing to brush your teeth properly could increase the risk of dying prematurely from cancer, researchers claim.
They found a link between high levels of dental plaque, or bacteria, and dying from cancer up to 13 years earlier than might otherwise be expected.
Those with the most bacteria on the surface of their teeth and gums had an 80 per cent increased risk of premature death.
Be thorough: Brushing your teeth badly can raise the risk of cancer, according to the latest research
Researchers say infection and inflammation play a role in up to one in five cancers, and is a key element in gum disease caused by dental plaque.
Gum disease causes bad breath, bleeding gums and, if untreated, cavities, receding gums and tooth loss after plaque settles between teeth and under the gumline.
It has been linked to chronic health problems including heart disease, thought to be caused by inflammation passing from the gums into the bloodstream, although US researchers have recently suggested the link may be coincidental.
Similarly, the Swedish researchers behind the latest study have admitted their findings do not prove a causal link between cancer and dental plaque. Poor mouth hygiene may be an indicator of other lifestyle factors associated with cancer.
The study tracked the health of 1,390 randomly selected adults from Stockholm for 24 years, starting in 1985.
All the participants were in their 30s and 40s at the start of the monitoring period, when they were questioned about factors likely to increase their cancer risk, such as smoking and wealth.
Their mouth hygiene was also assessed to find out their levels of dental plaque, tartar, gum disease, and tooth loss.
None had overt gum disease, but all had varying levels of plaque on the tooth and gum surface.
By 2009, 58 had died, around a third of whom were women (35 per cent). Of these deaths, 35 were caused by cancer.
The average age of death was 61 for the women and 60 for the men according to the study, published in the online journal BMJ Open.
A woman conducts a breast exam: Deaths among the women were predominantly caused by breast cancer
The women would have been expected to live around 13 years longer, and the men an additional 8.5 years, so their deaths could be considered premature, said study leader Professor Birgitta Soder, of the department of dental medicine at the Karolinska Institute, Huddinge.
Deaths among the women were predominantly caused by breast cancer, while those among the men were attributed to a range of different cancers.
The original dental plaque index in those who had died was higher than in those who had survived. They had values of 0.84 to 0.91, indicating that the gum and teeth surface had been covered with plaque.
The values among the survivors were consistently lower, between 0.66 to 0.67, indicating that their teeth and gums were only partially covered with plaque.
Even after known risk factors were considered such as age, smoking, lower educational attainment and frequency of dental visits, links between the amount of dental plaque and premature death remained strong.
However, the absolute risk of premature death was low.
Dr Paul Pharoah, reader in cancer epidemiology at the University of Cambridge, said the results suggested higher levels of plaque are associated with ‘higher all-cause mortality’.
‘Over the 24 years of follow-up the average death rate was two per thousand per year.
‘For the 2.5 per cent of the population with a plaque index about one higher than average (1.7 compared to 0.7) the average death rate would be about three per thousand per year.
‘That means that a small proportion of the population with the worst level of plaque are at a slightly increased risk of dying. This association may not be causal.’
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