3 Risk Factors for Cognitive Decline in Older Adults

November 30, 2017
Mark L. Fuerst

These common conditions may affect the risk of Alzheimer disease or the ability to cope with daily activities.

Elderly patients are prone to sleep apnea, heart disease, and depression. These conditions may affect the risk of Alzheimer disease or the ability to cope with daily activities, according to 3 new studies.1-3

Details of these studies-and their clinical implications-are briefly summarized here.

 

Study 1. Sleep Apnea Elevates Risk of Alzheimer Disease
Biomarkers for amyloid beta, the plaque-building peptides associated with Alzheimer disease, increase over time in elderly adults with obstructive sleep apnea (OSA).

The study
A 2-year prospective, longitudinal study included 208 participants, age 55 to 90, with normal cognition who were not depressed.1 More than half of the participants had OSA, including 36.5% with mild OSA and 16.8% with moderate to severe OSA.

The severity of OSA correlated with a decrease in cerebrospinal fluid amyloid beta levels over time, which is compatible with an increase in amyloid deposits in the brain. This finding was confirmed in a subset of participants who underwent amyloid PET, which showed an increase in amyloid burden in those with OSA.

Clinical implications
Several studies suggest sleep disturbances might contribute to amyloid deposits and accelerate cognitive decline in those at risk for Alzheimer disease. “Results from this study, and the growing literature suggesting that OSA, cognitive decline, and Alzheimer’s disease are related, may mean that age tips the known consequences of OSA from sleepiness, cardiovascular, and metabolic dysfunction to brain impairment,” said senior author Ricardo S. Osorio, MD, Assistant Professor of Psychiatry at New York University School of Medicine. “If this is the case, then the potential benefit of developing better screening tools to diagnose OSA in the elderly, who are often asymptomatic, is enormous.”

Study 2. Reduced Heart Function Linked to Brain’s Memory Center
Reductions in brain blood flow might explain clinical observations that link heart function to cognitive impairment, Alzheimer disease, and dementia.

The studyThe study included 314 participants, average age 73 years, in the Vanderbilt Memory & Aging Project.2 More than one-third (39%) had mild cognitive impairment. They had cardiac index measured with echocardiography, and blood flow in the brain measured with MRI.

Lower cardiac index was correlated with lower cerebral blood flow in the temporal lobe, a brain region critical for memory processing, but not in other regions of the brain.

Clinical implications
A growing body of research makes a strong connection between heart health and brain health. “We currently know a lot about how to prevent and medically manage many forms of heart disease, but we do not yet know how to prevent or treat Alzheimer’s disease,” said lead author Angela Jefferson, PhD, Director of the Vanderbilt Memory & Alzheimer’s Center. “This research is especially important because it may help us leverage our knowledge about managing heart health to address and treat risk factors for memory loss in older adults before cognitive symptoms develop.”

Study 3. Depressive Symptoms Correlate With Activities of Daily Living
The more depressed elderly people become, the more trouble they may have with activities of daily living.

The study
A community-based, prospective, observational study included 769 adults, aged 65 years and older, who could perform their daily functions.3 The participants were followed annually for 7.5 years for the presence of depressive symptoms and any dependence for activities of daily living.

At the study’s end, the researchers observed depressive symptoms in 232 of the 763 participants (30.4%). Those participants with depressive symptoms were more likely to have problems in performing their regular daily activities. There was no clear evidence that living circumstances or marital status had an effect on this association.

Clinical implications
Few published studies have investigated the possibility of an association between depressive symptoms and dependence in activities of daily living in elderly adults. “Our findings suggest that depressive symptoms are associated with future activities of daily living dependence and that living circumstances (except for institutionalization) and marital status do not affect the association,” the researchers stated.

References:

1. Sharma RA, Varga AW, Bubu OM, et al. Obstructive sleep apnea severity affects amyloid burden in cognitively normal elderly: a longitudinal study. Am J Respir Crit Care Med. 2017 Nov 10. doi: 10.1164/rccm.201704-0704OC. [Epub ahead of print]

2. Jefferson AL, Liu D, Gupta DK, et al. Lower cardiac index levels relate to lower cerebral blood flow in older adults. Neurology. 2017 Nov 8. DOI: https://doi.org/10.1212/WNL.0000000000004707. [Epub ahead of print]

3. Nakamura T, Michikawa T, Imamura H, et al. Relationship between depressive symptoms and activity of daily living dependence in older Japanese: The Kurabuchi Study. J Am Geriatr Soc. 2017 Sep 27. doi: 10.1111/jgs.15107. [Epub ahead of print]