Subjective health complaints and exposure to tick-borne infections in southern Norway

Acta Neurol Scand. 2020 Sep;142(3):260-266. doi: 10.1111/ane.13263. Epub 2020 May 26.


Objectives: Whether tick-borne infections can cause chronic subjective health complaints is heavily debated. If such a causal connection exists, one would expect to find more health complaints among individuals exposed to tick-borne infections than among non-exposed. In this study, we aimed to assess if exposure to tick-borne infections earlier in life, evaluated by examination of serum for IgG antibodies to tick-borne microbes, was associated with self-reported somatic symptom load.

Materials & methods: All individuals with residential address in Søgne municipality in southern Norway, aged 18-69 years, were invited to participate in the study. Blood samples were analyzed for IgG antibodies to different tick-borne microbes, and somatic symptom load was charted by the Patient Health Questionnaire-15 (PHQ-15).

Results: Out of 7424 invited individuals, 2968 (40.0%) were included in the study. We detected IgG antibodies to Borrelia burgdorferi sensu lato (Bb) in 22.9% (95% CI 21.4-24.4). Bb seropositive individuals reported less frequently moderate to severe somatic symptom load (ie, PHQ-15 sum score ≥ 10) than seronegative individuals (12.5% versus 17.7%, difference 5.2% [95% 2.1-8.0]). However, when adjusting for several other variables in a multivariable linear regression model, presence of serum IgG antibodies to Bb was not associated with somatic symptom load. Presence of IgG antibodies to other tick-borne microbes than Bb, or seropositivity to at least two microbes, was also not associated with somatic symptom load.

Conclusion: Presence of serum IgG antibodies to tick-borne microbes was not associated with self-reported somatic symptom load.

Keywords: PHQ; diagnostic self-evaluation; lyme borreliosis; medically unexplained symptoms; seroepidemiologic studies; tick-borne diseases.

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Animals
  • Cost of Illness
  • Female
  • Health Status
  • Humans
  • Immunoglobulin G / analysis
  • Lyme Neuroborreliosis / complications
  • Lyme Neuroborreliosis / epidemiology
  • Male
  • Middle Aged
  • Norway / epidemiology
  • Self Report
  • Sex Factors
  • Surveys and Questionnaires
  • Tick-Borne Diseases / complications*
  • Tick-Borne Diseases / epidemiology*
  • Tick-Borne Diseases / immunology
  • Young Adult


  • Immunoglobulin G