Cognition in adults with Williams syndrome-A 20-year follow-up study

Williams syndrome (WBS) is a genetic multisystem disorder. The main symptom is borderline (intelligence quotient, IQ 70-79) or abnormally low intelligence (IQ < 70). According to earlier studies young individuals with WBS demonstrate generally a slightly higher verbal IQ (VIQ) compared to performance/nonverbal IQ (PIQ). WBS was recognized as a distinct entity already about 60 years ago, but still cognition in adults with WBS is poorly known.

We followed 25 adults (age at baseline 19-68, median 38) with genetically confirmed WBS for about 20 years. The study subjects underwent medical and neuropsychological assessments at the baseline and at the end of follow-up.

The mean VIQ remained quite stable from early adulthood up to 40 years of age after which it declined. The mean PIQ kept on improving from early adulthood until 50 years of age after which it gradually declined. At the end of the study, all study subjects had at least two longstanding health problems out of which hypertension, psychiatric disorder, and scoliosis or kyphosis occurred most frequently. At end of the study, two patients suffered from vascular dementia. Seven patients died during the follow-up.

In adults with WBS, the course of cognition is uneven across the cognitive profile. Their verbal functions both develop and deteriorate earlier than performance/nonverbal functions. Frequent somatic co-morbidities may increase risk to shortened life span.