Prevalence of white matter hyperintensities in a young healthy population

White matter hyperintensities (WMHs) are bright objects observed in the white matter on brain magnetic resonance (MR) imaging. WMHs are often reported as "normal" findings but may represent pathological changes. The prevalence of WMHs appears to increase with increasing age although both the typical timing and clinical significance of their appearance among medically and neurologically healthy persons remains unclear. We assessed the prevalence of WMHs in a cohort of younger healthy subjects.

Our study comprised 243 healthy subjects ages 16-65 years from our prospective normative MR imaging database. MR scans were rated for presence of periventricular and centrum semiovale WMHs using a four-point visual semi-quantitative scale.

WMHs occurred in 5.3% (13 of 243) of subjects. All WMHs were small (rating of 0.5) except one subject age 65 years who had large WMHs (ratings of 2). The median age for subjects with no WMHs was 34.5 years compared to 57.0 years for subjects with WMHs. There were no gender differences (P= .76). Older age correlated with presence of WMHs (r = 0.24; P= .01). Age greater than 55 years had a 10-fold increase in the prevalence of WMHs compared to age < or =55 years (odds ratio = 10.01; 95% confidence interval = 3.1-32.3; P < .001).

WMHs were uncommon in a younger healthy population screened for comorbid diseases, but increased 10-fold in subjects over 55 years of age. When present, the WMHs are generally small (rating of 0.5). While large WMHs appear to be associated with cognitive deterioration, the optimum threshold for identification, clinical significance, and prognostic value of smaller white matter changes requires further research.