Soccer heading is associated with white matter microstructural and cognitive abnormalities

Abstract

Purpose: To investigate the association of soccer heading with subclinical evidence of traumatic brain injury.

Materials and methods: With institutional review board approval and compliance with HIPAA guidelines, 37 amateur soccer players (mean age, 30.9 years; 78% [29] men, 22% [eight] women) gave written informed consent and completed a questionnaire to quantify heading in the prior 12 months and lifetime concussions. Diffusion-tensor magnetic resonance (MR) imaging at 3.0 T was performed (32 directions; b value, 800 sec/mm(2); 2 × 2 × 2-mm voxels). Cognitive function was measured by using a computerized battery of tests. Voxelwise linear regression (heading vs fractional anisotropy [FA]) was applied to identify significant regional associations. FA at each location and cognition were tested for a nonlinear relationship to heading by using an inverse logit model that incorporated demographic covariates and history of concussion.

Results: Participants had headed 32-5400 times (median, 432 times) over the previous year. Heading was associated with lower FA at three locations in temporo-occipital white matter with a threshold that varied according to location (885-1550 headings per year) (P < .00001). Lower levels of FA were also associated with poorer memory scores (P < .00001), with a threshold of 1800 headings per year. Lifetime concussion history and demographic features were not significantly associated with either FA or cognitive performance.

Conclusion: Heading is associated with abnormal white matter microstructure and with poorer neurocognitive performance. This relationship is not explained by a history of concussion.

Figure 1a:

(a, b) Three ROIs in the temporo-occipital white matter detected by the initial voxelwise linear regression of estimated prior 12 months of heading on FA, shown as color regions rendered in three-dimensional images (a) and superimposed on T1-weighted axial (left), coronal (middle), and sagittal (right) images from the Montreal Neurological Institute template (b). FA at each ROI was significantly lower as a function of greater heading exposure. R = right.

Figure 1b:

(a, b) Three ROIs in the temporo-occipital white matter detected by the initial voxelwise linear regression of estimated prior 12 months of heading on FA, shown as color regions rendered in three-dimensional images (a) and superimposed on T1-weighted axial (left), coronal (middle), and sagittal (right) images from the Montreal Neurological Institute template (b). FA at each ROI was significantly lower as a function of greater heading exposure. R = right.

Figure 2a:

(a–c) Inverse logit fits for mean FA values from each of the three ROIs (Fig 1) and (d) for memory versus heading exposure. Observed values and the fitted inverse logit function are expressed in blue circles and black curves, respectively. Light-gray line = estimated threshold (β₂) and its 95% confidence interval = black line with double-sided arrows, red box = mean FA and memory performance values.

Figure 2b:

(a–c) Inverse logit fits for mean FA values from each of the three ROIs (Fig 1) and (d) for memory versus heading exposure. Observed values and the fitted inverse logit function are expressed in blue circles and black curves, respectively. Light-gray line = estimated threshold (β₂) and its 95% confidence interval = black line with double-sided arrows, red box = mean FA and memory performance values.

Figure 2c:

(a–c) Inverse logit fits for mean FA values from each of the three ROIs (Fig 1) and (d) for memory versus heading exposure. Observed values and the fitted inverse logit function are expressed in blue circles and black curves, respectively. Light-gray line = estimated threshold (β₂) and its 95% confidence interval = black line with double-sided arrows, red box = mean FA and memory performance values.

Figure 2d:

(a–c) Inverse logit fits for mean FA values from each of the three ROIs (Fig 1) and (d) for memory versus heading exposure. Observed values and the fitted inverse logit function are expressed in blue circles and black curves, respectively. Light-gray line = estimated threshold (β₂) and its 95% confidence interval = black line with double-sided arrows, red box = mean FA and memory performance values.