Cognitive performance during senescence in untreated congenital isolated GH deficiency

Abstract

Individuals with untreated isolated GH deficiency (IGHD) due to a mutation in the GHRH receptor gene from Itabaianinha Brazil have increased insulin sensitivity, normal life expectancy, and an extended health span, i.e. the period of life free from disabilities. We hypothesize that their prolonged health span is accompanied by a delayed cognitive decline in senescence. To test this hypothesis, we have administered the Literacy-Independent Cognitive Assessment (LICA) to 15 IGHD individuals aged over 50 years and 15 controls matched by age, sex, years of education, and percentage of illiteracy. All individuals were negative for HIV and syphilis serology, and there were no differences in serum levels of folate, vitamin B12 and TSH between the two groups, while free T4 was higher in the IGHD group. IGHD subjects had a higher total LICA score than controls, 215 (22.7) vs 204.2 (18.1), without reaching statistical significance. Scores of memory, visuoconstruction, language and calculation were similar between the two groups, with better attention (9.5 (1.4) vs 8.3 (1.1), P = 0.01) and executive function (38.3 (4.8) vs 35.1 (2.5), P = 0.03) scores in IGHD. MANCOVA revealed that group (but no age) had a significant effect on the LICA variables (partial eta squared of 0.455, power of 0.812, P = 0.02). This effect is verified on attention (partial eta squared 0.216, power of 0.749, P = 0.01) and executive function (partial eta squared 0.154, power of 0.570, P = 0.03. In conclusion, IGHD in senescence is associated with similar total cognitive performance but better attention and executive function than controls.