BACKGROUND: Lyme neuroborreliosis (LNB) caused by the tick-borne spirochetes of the Borrelia burgdorferi sensu lato species complex has been suggested to be associated with a range of neurological disorders. In a nationwide population-based cohort-study we examined the association between LNB and dementia, Alzheimer's disease, Parkinson's disease, motor neuron disease, epilepsy and Guillain-Barré syndrome.

METHODS: We used national registers to identify all Danish residents diagnosed during 1986-2016 with LNB (n=2,067) and a gender and age matched comparison cohort from the general population (n=20,670), and calculated risk estimates and hazard ratios (HR).

RESULTS: We observed no long-term increased risk of dementia, Alzheimer's disease, Parkinson's disease, motor neuron diseases or epilepsy. However, within the first year eight (0.4%) of the LNB patients developed epilepsy compared with 20 (0.1%) of the comparison cohort (difference 0.3%, 95% CI: 0.02% to 0.6%). In the LNB group 11 (0.5%) patients were diagnosed with Guillain-Barré syndrome within the first year after LNB diagnosis compared with 0 (0.0%) in the comparison cohort. After the first year, the risk of Guillain-Barré was not increased.

CONCLUSION: LNB patients did not have increased long-term risk of dementia, Alzheimer's disease, Parkinson's disease, motor neuron diseases, epilepsy or Guillain-Barré. Although absolute risk is low, LNB patients might have an increased short-term risk of epilepsy and Guillain-Barré syndrome.