High cognitive reserve results in better neurocognitive performance in bipolar disorder

Cognitive reserve in bipolar patients gives a possible explanation for the differences seen among patients in their ability to perform in neurocognitive tests.
Cognitive reserve in bipolar patients gives a possible explanation for the differences seen among patients in their ability to perform in neurocognitive tests.

Patients with bipolar disorder who had high cognitive reserve performed better in tests of attention, verbal fluency, and verbal memory than those with low cognitive reserve, indicating that cognitive reserve may be valuable in predicting neurocognitive performance in those with premorbid bipolar disorder, according to findings were published in the Journal of Affective Disorders.

Researchers from Spain recruited 102 participants from the Bipolar Disorders Program of the Hospital Clinic of Barcelona who met DSM-IV criteria for bipolar I or II, and who were euthymic (YMRS ≤ 6 and HDRS ≤ 8) for 6 months, as well as 32 healthy controls.

Participants underwent a neuropsychological assessment that evaluated premorbid IQ, frontal executive functions, attention, working memory, verbal fluency, and verbal learning and memory.

Participants' Cerebral Reserve Score (CRS) was derived from estimated IQ, educational level, and occupational achievement, and a group CRS median was calculated (P50= 181.05). Participants with cognitive reserve scores above the median were considered to have high cognitive reserve, and those with cognitive reserve scores below the median were considered to have low cognitive reserve.

After multivariable adjustment for potential confounders, such as number of admissions and prior psychotic symptoms, participants with high cognitive reserve had better performance in attention (digits forward: F= 4.554, P=.039), phonemic and semantic verbal fluency (FAS: F= 9.328, P=.004; and Animal Naming: F= 8.532, P=.006), and verbal memory (short cued recall of California Verbal Learning Test: F= 4.236, P =.046).

The researchers noted that this means cognitive reserve may be a moderator of neurocognition in patients with bipolar disorder.

“The concept of cognitive reserve thus gives a possible explanation for the differences seen among patients diagnosed with bipolar disorder in their capacity to deal with neuropathology,” wrote Iria Grande, MD, PhD, from the Hospital Clínic de Barcelona and colleagues.

They also noted that similar to in Alzheimer's disease, neurocognitive decline in bipolar patients with high cognitive reserve may be seen later than in patients with low cognitive reserve, because pathology is tolerated longer.

“Specific programs addressed to improve cognition and functioning conducted in the early stages of the illness, or even at a premorbid stage in patients at risk for bipolar disorder, may be highly valuable in order to boost cognitive reserve and thus, prevent cognitive decline,” the authors concluded.

However, this field of research is still in its early stages, and large-scale prospective studies are warranted to confirm this hypothesis.

Limitations

  • The study's sample size was small, which may have limited some results
  • The study's cross-sectional design does not allow inferences about causation to be made
  • Because there is not much consensus on cognitive reserve, it is difficult to compare cognitive reserve assessment with existing research
  • Since this study was conducted in a specialized care center, results may not be generalizable to other settings
  • The possible effect of pharmacological treatment and comorbid substance use on cognitive reserve was not studied

Reference

Grande I, Sanchez-Moreno J, Sole B, et al. High cognitive reserve in bipolar disorders as a moderator of neurocognitive impairment. J Affect Disord. 2016; doi:10.1016/j.jad.2016.10.012

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