Ecological momentary assessment of cognitive symptoms in individuals with phenylketonuria

Abstract

Phenylketonuria (PKU) is a rare autosomal recessive condition characterized by mutations in the gene encoding the phenylalanine hydroxylase (PAH) enzyme that is necessary for the metabolism of the amino acid phenylalanine (Phe). When not properly metabolized, excess Phe can have disruptive effects on the brain. Although early identification and intervention largely prevent severe impairments associated with untreated PKU, individuals with early-treated PKU continue to experience some neurological and neurocognitive impairment. The neurocognitive profile of early-treated PKU is characterized by a slight decrease in overall intellectual functioning and circumscribed disruptions in executive function, attention, processing speed, and fine motor control. The present study represents the first to measure “in-the-moment” symptoms of cognition in individuals with early-treated PKU through use of ecological momentary assessment (EMA). We recruited a sample of 27 adults with early-treated PKU and 26 adults without PKU. Participants completed a short eight-item PKU-specific cognitive symptom survey called the EASSI-EMA four times a day for seven days. In-the-moment response data was also compared to data from a retrospective version of the measure, neurocognitive performance data, and blood Phe levels. As expected, the PKU-group reported higher cognitive symptom severity across the week as compared to the non-PKU group. In addition, individuals with PKU performed poorer in task-based measures of cognition. Contrary to expectations, there was not a significant relationship between blood Phe level and neurocognitive symptoms or task performance. The present findings demonstrate the feasibility and potential value of utilizing EMA methodology to capture in-the-moment, day-to-day functioning in individuals with PKU and other rare metabolic conditions.