Abstract
Background:High education level and high occupational complexity have been implicated as risk factors for Parkinson’s disease (PD).Objective:The objective was to determine whether cognitive capacity, measured as IQ, in early adulthood is associated with the subsequent development of PD.Method:Data on IQ were retrieved from the Swedish Military Service Conscription Registry, comprising Swedish males who enlisted for military service in the period 1968–1993 (N = 1,319,235). After exclusion, 1,189,134 subjects in total were included in the present study. Individuals who later developed PD (N = 1,724) were identified using the Swedish National Patient Register and the Swedish Cause of Death Register.Results:High education level was associated with PD. High IQ was associated with PD (p < 0.0001), both when analyzed as a continuous variable and when divided into three categories. The hazard ratio for the high IQ category compared to the low IQ category was 1.35 (95% confidence interval 1.17–1.55). Strong test results on the subtests, measuring verbal, logic, visuospatial and technical abilities, were also associated with PD. In a subgroup, smoking was inversely associated with PD, as well as with IQ.Conclusions:This study identifies high IQ to be a risk factor for PD.
Highlights
It has been reported that high level of education is a risk factor for Parkinson’s disease (PD) [1, 2]
Fardell et al / High IQ is Associated with Parkinson’s Disease and healthcare services, clerkship, social science, law and library jobs, and farming, many but not all of which require a high level of education [4,5,6,7]
The present study is based on data retrieved from the Swedish Military Service Conscription Registry, comprising all Swedish males who were born in the period of 1949–1975, who enlisted for military service in the period of 1968–1993 (N = 1,319,235)
Summary
It has been reported that high level of education is a risk factor for Parkinson’s disease (PD) [1, 2]. C. Fardell et al / High IQ is Associated with Parkinson’s Disease and healthcare services, clerkship, social science, law and library jobs, and farming, many but not all of which require a high level of education [4,5,6,7]. Most of the discussions regarding associations between PD and education and occupations have focused on the possibility that certain occupations may increase the risk for PD by exposure to environmental factors, such as toxins (e.g., in farming) or infections (e.g., in teaching and healthcare services). High education level and high occupational complexity have been implicated as risk factors for Parkinson’s disease (PD). Conclusions: This study identifies high IQ to be a risk factor for PD
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