Periodontitis linked to faster cognitive decline in people with Alzheimer’s

A number of studies have demonstrated that poor oral hygiene, a common problem among elderly patients, is a risk factor for developing Alzheimer’s disease. Now, a joint research project led by scientists at the University of Southampton and King’s College London has provided further evidence that periodontitis could be associated with increased dementia severity and a more rapid cognitive decline in Alzheimer’s patients.

Fifty-nine non-smoking patients with an average age of 77.7, mild to moderate dementia and a minimum of ten teeth who had not received treatment for periodontitis in the past six months participated in the study. The patients underwent dental examinations by a dental hygienist at baseline and at the six-month follow-up. In addition, blood samples were taken to measure inflammatory markers in their blood.

The presence of periodontal disease at baseline was associated with a sixfold increase in the rate of cognitive decline in participants over the study period. Periodontitis at baseline was also associated with a relative increase in the pro-inflammatory state over the follow-up period. The researchers concluded that periodontal disease is associated with an increase in cognitive decline in Alzheimer’s disease, possibly via mechanisms linked to the body’s inflammatory response.

As the study only included a limited number of participants, the authors stated that the findings should be validated in a larger-cohort study. In addition, they highlighted that the precise mechanisms by which periodontitis may be linked to cognitive decline are not fully understood and other factors might also play a part in the decline seen in participants’ cognition alongside their oral health. However, the current evidence is sufficient to explore whether periodontal treatment might benefit the treatment of dementia and Alzheimer’s disease, they said.

Periodontitis is a common disease in older people. The World Health Organization estimates that 15–20 per cent of adults aged 35–44 worldwide have severe periodontal disease. The condition may become more common in Alzheimer’s disease because of a reduced ability to take care of oral hygiene as the disease progresses. Higher levels of antibodies to periodontal bacteria are associated with an increase in levels of inflammatory molecules elsewhere in the body, which in turn has been linked to greater rates of cognitive decline in Alzheimer’s disease in previous studies.

Dr Mark Ide, from King’s College London Dental Institute and first author on the paper, said: “Gum disease is widespread in the UK and US, and in older age groups is thought to be a major cause of tooth loss. In the UK in 2009, around 80 per cent of adults over 55 had evidence of periodontal disease, while 40 per cent of adults aged 65–74 and 60 per cent of those older than 75 had less than 21 of their original 32 teeth, with half of them reporting periodontitis before they lost teeth.”

The study, titled “Periodontitis and cognitive decline in Alzheimer’s disease”, was published online on 10 March in the PLOS ONE journal.