T36. TRAJECTORIES OF CURRENT AND PREMORBID IQ IN SCHIZOPHRENIA SPECTRUM DISORDERS: A 10-YEAR FOLLOW-UP STUDY. (9th April 2019)

• Record Type: Journal Article
• Authors: Flaaten, Camilla Bärthel; Melle, Ingrid; Simonsen, Carmen; Bjella, Thomas; Engen, Magnus Johan; Haatveit, Beathe; Vaskinn, Anja; Ueland, Torill
• Is Part Of: Schizophrenia bulletin. Volume 45(2019)Supplement 2
• Page Start: S217
• Page End: S217
• Publication Date: 2019-04-09
• Subjects: Schizophrenia -- Periodicals; Schizophrenia -- Research -- Periodicals; 616.898005
• DOI: 10.1093/schbul/sbz019.316
• Languages: English
• ISSNs: 0586-7614

Abstract

Abstract: Background: Neurocognitive impairment is a core feature of schizophrenia strongly related to functional outcome. The presence and severity of deficits varies between individuals, with some showing considerably impaired and others relatively intact performance. Tracking the development of cognitive functioning over time and investigating the relationship to other clinical features and outcome, is an important step towards more targeted interventions. Impairments are found in a range of cognitive domains, as well as in both premorbid and current IQ. Premorbid IQ measures are used to investigate decline before and during the course of illness, compared to current IQ. Longitudinal studies generally show stability over time for IQ measures, although few long-term follow-up (fu) studies exist. Thus, this study explored long-term trajectories of premorbid and current IQ, using 10-year fu data. Methods: The sample consists of 33 patients with schizophrenia-spectrum disorders and 92 healthy controls recruited to the TOP study in Norway. Comprehensive clinical and neurocognitive assessments were conducted at baseline and 10-year fu. Premorbid IQ was measured using WASI and current IQ using NART. Thirty-three patients and 89 controls completed the WASI and 30 patients and 92 controls completed the NART at both time-points. Premorbid IQ was estimated from NART error scores using the Norwegian validated formula correcting for age and years of education. Due to missing data only 28 patients and 83 controls were included in this analysis. More cases are being included consecutively. Results: Mean WASI IQ scores for patients were 104.9 (SD 15.3) at baseline and 108.6 (SD 16.2) at fu. For controls, WASI IQ scores were 115.4 (SD 8.4) at baseline and 118.9 (SD 8.5) at fu. For patients, NART error scores ere 19.2 (SD 10.5) at baseline and 17.0 (SD 9.3) at fu, while controls made 14.8 (SD 7.8) errors at baseline and 14.4 (SD 7.4) at fu. For patients, the mean NART IQ scores were 109.7 (SD6.9) at baseline and 109.7 (SD 6.5) at fu. Controls had scores of 113.6 (SD5.0) and 113.6 (SD 4.5) at respectively baseline and fu. Repeated-measures ANOVA showed that patients scored significantly lower than controls on all measures: WASI IQ, F(1, 120) = 24.15, p < 0.000, NART error scores F(1, 120) = 4, 35, p = 0, 039 and NART IQ, F(1, 110) = 14.04, p < 0.000. For WASI IQ scores, there was a significant effect of time, F(1, 120) = 27.49, p > 0.000), but no time*group interaction. For NART error scores, there was a significant effect of time, F(1, 120) = 9.97, p = 0.002, and a time*group interaction, F(1, 120) = 4.57, p=0.035). There was no significant main effect of time or time*group interaction for NART IQ scores. Discussion: In line with other studies, lower IQ was found in the schizophrenia-spectrum group, both at baseline and 10-year fu. Results indicate small, but significant improvements in current IQ as measured by the WASI, as well as NART error scores for both groups. Although NART error scores improved slightly more for patients than controls, estimated premorbid IQ from NART scores was stable across time for both groups. These preliminary findings show slight improvement in current IQ, while premorbid IQ shows a high degree of stability across 10 years. Although small increases are found in WASI scores, they support existing literature finding long-term stability in IQ.