The association of periodontal inflammation and inflammatory markers with cognitive dysfunction: A case–control study

Background This study investigated the association of inflammatory markers in saliva, plasma, and cerebrospinal fluid (CSF) with cognitive decline and periodontitis. Methods Patients with Alzheimer disease (AD, n = 52), mild cognitive impairment (MCI, n = 51), subjective cognitive decline (SCD, n = 51), and controls ( n = 76) between 50 and 80 years were included. Participants underwent an oral examination, and blood and stimulated saliva were collected. In addition, CSF samples were collected from patients but not controls. Levels of interleukin (IL)‐1β, IL‐8, IL‐10, IL‐17A, and tumor necrosis factor‐alpha (TNF‐α) were analyzed by multiplex immunoassays. Results Increased salivary levels of IL‐1β, IL‐10, and IL‐17A were found in MCI compared to controls, while in plasma increased IL‐8 levels were seen in all 3 patient groups compared to controls ( p < 0.001). TNF‐α plasma levels were higher in SCD and AD ( p < 0.05). IL‐17A levels in CSF were higher in participants with no/mild periodontitis compared to generalized periodontitis ( p = 0.023). Participants with severe periodontitis showed higher levels of IL‐8 both in saliva ( p = 0.027) and plasma ( p < 0.001), as well as higher TNF‐α levels in plasma ( p = 0.041). Conclusions Inflammation markers could indicate an increased risk for cognitive decline, especially in cases of more severe periodontitis. Plain Language Summary Evidence has indicated an association between periodontitis and cognitive impairment. Hence, this study investigated whether inflammatory markers in saliva, plasma, and cerebrospinal fluid are associated with cognitive decline. Cases with mild or more severe signs of cognitive impairment had more signs of periodontal disease. Levels of some, but not all, inflammation markers were elevated among patients compared to cognitively healthy controls. Oral inflammation could indicate an increased risk for cognitive decline, and chronic inflammation may act as a common pathway. Early periodontal intervention and maintaining oral health may contribute to cognitive well‐being.