Demographic and clinical characteristics of the patient and comparison groups are presented in t1. Group differences for age (F=2.65, df=2, 62, p=0.08), sex composition (χ2=2.16, df=2, p=0.34) and handedness (χ2=1.28, df=2, p=0.53) were not significant. However, the late onset group completed significantly fewer years of education than the comparison subjects (F=4.30, df=2, 62, p=0.02). The patient groups were also significantly more depressed (F=29.91, df=2, 62, p=0.001) and anxious (F=12.32, df=2,62, p=0.001) than the comparison subjects. The early and late onset patient groups did not differ with respect to symptom severity (F=0.41, df=1, 36, p=0.97) on the YBOCS, percentage of patients with comorbid depressive (χ2=1.59, df=1, p=0.26) or anxiety disorders (χ2=2.34, df=1, p=0.18), or percentage of patients receiving psychotropic medication (χ2=0.49, df=1, p=0.49).
Descriptive statistics for neuropsychological test variables are presented in t2. Results revealed that both patient groups recalled significantly less information on LM-I (F=14.09, df=2,62, p=0.001) and LM-II (F=15.53, df=2,62, p=0.001) than the comparison group. The late onset group also took longer to complete TMT-B (F=4.00, df=2,62, p=0.02) and made more errors on the Self-Ordered Pointing Test (F=5.33, df=2,62, p=0.007) than both the early onset and comparison groups, showed poorer delayed recall of the Rey Complex Figure (F=7.63, df=2,62, p=0.001), and had a lower digit span (F=4.04, df=2,62, p=0.02) than the early onset group. All group differences remained significant when controlling for education, depression or anxiety using analysis of covariance (p<0.05). No significant group × sex interaction was observed for any of the neuropsychological variables (p>0.05).