The Influence of Level of Education on Instrumental Activities of Daily Living in Patients with Alzheimer’s Disease.

Abstract

Background: According to the “brain-reserve hypothesis” in Alzheimer’s disease (AD), patients with more years of education are expected to have higher cognitive status during adulthood. Hence, they might have a relatively larger burden of AD pathology and a more advanced level of the disease when dementia is clinically evident. Higher educated people would also be expected to perform better on standardized cognitive tests that use a single threshold to identify dementia, such as Mini-Mental State Examination (MMSE). These factors might lead to a later manifestation of the typical symptoms of AD and detection of the disease. Thus, diagnosis and treatment might occur in a later stage, which may impair the results of AD therapy. The period in which higher educated individuals experience clinical AD might be shortened, with faster disease progression and earlier death. A higher education level has been associated with more rapid cognitive decline in several studies; however, the relationships between functional abilities and education are less investigated. Objectives: This long-term study aimed to investigate the potential associations between years of education and aspects of Instrumental Activities of Daily Living (IADL) capacity in AD. Methods: The Swedish Alzheimer Treatment Study (SATS) is a prospective, observational multicenter study used for assessing longitudinal effectiveness of cholinesterase inhibitor (ChEI) treatment in a routine clinical setting. Among the 1,258 outpatients clinically diagnosed with probable or possible AD, 1,021 had mild-to-moderate AD (MMSE score, 10–26) at the start of ChEI therapy (baseline). Of these, 767 individuals had lower (<=9 years) and 252 had higher (>9 years) education level, and education level was missing for 2; thus, 1,019 patients were enrolled in the present study. Participants were assessed for cognitive (MMSE) and functional performance (IADL and Physical Self-Maintenance Scale [PSMS]) at baseline and every 6 months for 3 years. The date of death was recorded over 20 years. Cox proportional-hazards regression was used to determine characteristics that affected survival: sex, number of apolipoprotein E e4 alleles, solitary living, duration of AD, age at baseline, specific concomitant medications, and cognitive and functional abilities at baseline and their rates of deterioration. Results: The IADL status at baseline was worse in patients with lower education than those with higher education, mean (95% confidence interval [CI]) 16.3 (15.9–16.7) vs. 14.9 (14.2–15.6) points, p < 0.001. The higher educated group demonstrated faster IADL progression, but not cognitive decline, from the 24-month assessment and onwards (p < 0.011). The IADL capacity was already markedly impaired at baseline; about 45–65% of the participants with higher education and 55–75% of those with lower education were dependent on assistance to perform these activities (IADL score, 2–5). The percentage of patients with impairment in the individual IADL items: “ability to use telephone,” “shopping,” “mode of transportation,” and “responsibility for own medications” and “ability to handle finances,” was significantly lower at baseline in the higher educated cohort. After 3 years, the IADL capacity had deteriorated further; 70–90% of the remaining participants still living at home in both groups could not perform these tasks independently. No significant difference in any of the individual IADL items was found between the groups. Thus, the patients with higher education showed faster deterioration in the abovementioned tasks during the 3-year study.
After 20 years of follow-up, 733 (96%) of the participants with lower education and 231 (92%) of those with higher education had died, p = 0.017. Patients with lower education were older at death than those with higher education, mean (95% CI) 82.9 (82.4–83.3) vs. 80.2 (79.2–81.2) years, p < 0.001). In the Cox regression models, risk factors for shorter lifespan in all individuals were male sex, older age, and faster basic ADL progression. In the lower educated cohort, use of antidiabetics or antihypertensive/cardiac therapy, worse cognitive or basic ADL capacity at baseline, and more rapid cognitive decline were independently observed to decrease survival time. In participants with higher education, lower IADL performance at baseline predicted shorter life expectancy. Conclusion: The present study highlights the clinical importance of functional evaluations in AD. Participants with lower education, who were ~2.5 mean years older, had worse functional status at baseline than those with higher education; however, the higher educated group deteriorated faster over a longer time in several individual IADL items. The patients with higher education were almost 3 years younger at death, on average. Common risk factors for death, such as use of antihypertensive/cardiac therapy or antidiabetics and cognitive impairment, were found in lower educated, but not in higher educated individuals. IADL capacity at baseline was an important predictor of survival in participants with higher education only. These results indicate that the consequences of dementia, such as cognitive and functional outcomes and comorbidities, have different impacts on the course of AD and prognosis in patients with various levels of cognitive reserve.

• author: Wattmo, Carina
• organization: Clinical Memory Research (research group); MultiPark: Multidisciplinary research focused on Parkinson´s disease; EpiHealth: Epidemiology for Health
• publishing date: 2021
• type: Contribution to conference
• publication status: published
• subject: Neurology
• conference name: 14th Clinical Trials on Alzheimer's Disease Conference
• conference location: Boston, United States
• conference dates: 2021-11-09 - 2021-11-12
• language: English
• LU publication?: yes
• id: 4a19ca9f-7fe3-4205-8c59-491312d7a062
• date added to LUP: 2021-11-26 14:53:47
• date last changed: 2021-11-29 09:30:46