Neurocognitive factors influencing inequalities in aging and brain damage
On March 18th, at 11.00 a.m. Raffaella Ramiati, full professor at the (Scuola Internazionale Superiore di Studi Avanzati SISSA, Trieste) presents the seminar "Neurocognitive factors influencing inequalities in aging and brain damage". The seminar will take place in Aula 3 (Scuola Superiore Sant'Anna). Click here to join the meeting via Microsoft Teams.
Abstract
Patients with the same neurological disease and comparable brain damage often display different functional outcomes. For instance, more than 25% of elderly individuals with no sign of cognitive impairment meet post-mortem pathological criteria of Alzheimer’s disease. By the same token, 10% to 40% of individuals with mild to moderate brain pathology showed no clinical symptoms of dementia. To account for this divergence between clinical symptoms and brain damage, the construct of cognitive reserve (CR) was put forward. This concept is operationalized by indirect measures, by linking cognitive performance to the combined influence of variables like, for instance, education, IQ, occupation, and lifestyle. The hypothesis is that an individuals’ CR helps them maintain or improve their cognitive performance in the face of pathological events, through yet unspecified compensatory mechanisms. Support for the CR hypothesis comes mainly from the observation that better education correlates with both a higher level of cognitive functioning and the delayed onset of cognitive decline, both for normal aging and for dementia, while low education is a risk factor for dementia and exacerbates its development. In addition, a patient’s high level of education is associated with less severe post-stroke cognitive deficits, and a low level of education, analogously to a low premorbid IQ, increases vulnerability to cognitive impairment after traumatic brain injury. Education has also been shown to affect patients with multiple sclerosis and Alzheimer’s disease. In a first retrospective study (Mondini et al. 2021) we quantified the relative contribution of age and sex as demographic factors, comorbidity, education, and occupation as CR proxies in accounting for cognitive aging. All participants (3,081) were evaluated at baseline with a complete neuropsychological test battery (T1) and those with unimpaired profiles were classified as Subjective Cognitive Decline, those mildly impaired as Mild Neurocognitive Decline, and those severely impaired as Major Neurocognitive Decline. From the first assessment 543 individuals were assessed a second time (T2), and 125 a third time (T3). Depending on whether they maintained or worsened their profile, participants were then classified as resistant or declining. Results showed that, in addition to age, at baseline education and occupation were the best predictors of all patients’ performance. Furthermore, across assessments, the resistant had higher levels of education and occupation than the declining. In particular, the Subjective Cognitive Decline, and all other groups included the most severely impaired, education and occupation predicted cognitive performance. In the second study (Tomasino et al. in prep.), we measured the contribution of CR, indexed by demographic and social background, education, occupational status, and whether they live in a large city or in a rural environment, to account for the patients’ cognitive individual differences caused by brain tumors. A large sample of around 700 patients, diagnosed with a brain tumor, received a MRI brain examination, and performed a battery of eleven different tests measuring their cognitive abilities before they underwent neurosurgery. We controlled for type, side, site, and size of the lesion, and for age and gender, in order to cast out the effect of cognitive reserve. The analysis was conducted with a separate statistical analysis of the eleven cognitive outcomes. We found a robust positive effect of education, and also, if less precisely determined, of professional background and of the nature of the urban environment of the patient’s residence. Moreover, substantial differences in these effects seem to depend on the cognitive function and on the cerebral hemisphere where the lesion occurred. This study establishes the role of CR, in addition to the neurological variables, in explaining the patients’ individual differences in cognitive functions caused by brain tumors