Borrelia burgdorferi as a risk factor for Alzheimer's dementia and mild cognitive impairment

To determine the association of Borrelia burgdorferi infection with Alzheimer's disease or mild cognitive impairment (MCI) in older adults.

Case-control study. Patients older than 60 years, both sexes, were included. Three groups were created: with probable Alzheimer's disease cases with NINCDS-ADRDA criteria, MCI cases in those not meeting NINCDS-ADRDA criteria for dementia, but who had an abnormal cognitive evaluation and independence in instrumental activities of daily living (IADL), cognitively healthy controls were diagnosed with normal cognitive evaluation and independence in IADL were identified in the community. Western blot IgG against B. burgdorferi in serum was done in all the participants. Non-conditional logistic regression was applied to estimate the association of Alzheimer's disease or MCI and seropositive to B. burgdorferi.

Thirty-eight patients with Alzheimer's disease, mean age of 75.6 ± 3.4 years, 69% were females, education 8.3 ± 4.8 years. 39 patients with MCI, mean age of 72.2 ± 6.8 years, 85% were females, education 11.2 ± 4.2 years. A total of 11/38 (29%) were positive to B. burgdorferi with Alzheimer's disease, 9/39 (23%) with MCI, and 11/108 (10%) of controls. In patients with Alzheimer's disease, an adjusted odds ratio (aOR) = 3.65 (95% CI 1.2-11.1) adjusted for education and a history of cerebrovascular disease (CVD) was estimated, and in patients with MCI an aOR = 3.2 (95% CI 1.1-9.1) for a history of diabetes mellitus and CVD was estimated.

In our study, there was an increased risk of Alzheimer's disease and MCI in seropositive IgG patients to B. burgdorferi.