3 New Studies on Dementia

August 10, 2018

New data indicate that dementia is largely undiagnosed or unrecognized; exposure to general anesthesia and surgery can lead to a subtle decline in memory and thinking skills in older adults; and sarcopenic obesity in older adults may predict dementia.

Dementia among older adults can often be a subtle illness. Three new studies show that the majority of older adults with dementia are either undiagnosed or unaware of the diagnosis; exposure to general anesthesia and surgery can lead to a subtle decline in memory and thinking skills in older adults; and sarcopenic obesity in older adults may predict dementia.

A substantial majority of older American adults with probable dementia have never been professionally diagnosed or are unaware they have been. A cross-sectional, observational study included 585 adults, age 65 and older, in the National Health and Aging Trends Study who met criteria for probable dementia in 2011 and had 3 years of continuous, fee-for-service Medicare claims prior to 2011. A multivariable logistic regression found more than half (58.7%) of the adults were either undiagnosed (39.5%) or unaware of the diagnosis (19.2%). Those who were Hispanic, had less than high school education, attended medical visits alone, or had fewer functional impairments were more likely to be undiagnosed.

Clinical Implications: “There is a huge population out there living with dementia who don’t know about it. The implications are potentially profound for health care planning and delivery, patient-physician communication and much more,” said lead author Halima Amjad, MD, MPH, assistant professor of medicine at the Johns Hopkins University School of Medicine. “If dementia is less severe and people are better able to perform day-to-day tasks independently, symptoms of cognitive loss are more likely masked, especially for patients who visit the doctor without a family member or friend who may be more aware of the patient’s symptoms.”

Source: Amjad H, Roth DL, Sheehan OC, et al. Underdiagnosis of Dementia: an Observational Study of Patterns in Diagnosis and Awareness in US Older Adults. J Gen Intern Med. 2018;1133-1138.

In adults over aged 70 years, exposure to general anesthesia and surgery is associated with a subtle decline in memory and thinking skills, which could be meaningful for those who already have low cognitive function or pre-existing mild cognitive impairment. An analysis of the longitudinal cognitive function trajectory in 1819 older adults assessed the rate of change in cognition over time, and its association with exposure to anesthesia and surgery. The subjects were followed for a median of 5 years. Those exposed to surgery and anesthesia during the period 20 years before enrollment had a small cognitive decline as compared to those who were not exposed. Cognitive impairment could be attributed to declines in memory and attention/executive cognitive domains.

Clinical Implications: “We need to be sure that patients considering surgery, and their families, are properly informed that the risk of cognitive dysfunction is possible,” said senior author Juraj Sprung, MD, PhD, a Mayo Clinic anesthesiologist. “In addition, alternative strategies should be discussed with patients before surgery is undertaken for those deemed to be at high risk. This study provides further reasons for clinicians to start performing routine preoperative cognitive evaluations of the elderly to further clarify an individual’s risk of exposure to surgery and anesthesia.”

Source: Schulte PJ, Roberts RO, Knopman DS, et al. Association between exposure to anaesthesia and surgery and long-term cognitive trajectories in older adults: report from the Mayo Clinic Study of Aging. Brit J Anaesthesia. Br J Anaesth. 2018;121:398-405.

Sarcopenic obesity can be used in clinical practice as an indicator of probable cognitive impairment in older adults. A cross-sectional analysis included a total of 353 participants, average age 69 years, who had either sarcopenia or obesity, or both. These two diseases have both been shown to have a negative impact on cognitive function. Both sarcopenia and obesity were associated with lower executive function, including working memory, mental flexibility, self-control and orientation, when assessed independently. Those with sarcopenic obesity showed consistent evidence of poor global cognitive performance.

Clinical Implications: “Sarcopenia has been linked to global cognitive impairment and dysfunction in specific cognitive skills including memory, speed, and executive functions,” said senior author James E. Galvin, MD, MPH, associate dean for clinical research and a professor of integrated medical science in Florida Atlantic University. “Understanding the mechanisms through which this syndrome may affect cognition is important as it may inform efforts to prevent cognitive decline in later life by targeting at-risk groups with an imbalance between lean and fat mass. They may benefit from programs addressing loss of cognitive function by maintaining and improving strength and preventing obesity.”

Source: Tolea MI, Chrisphonte S, Galvin JE. Sarcopenic obesity and cognitive performance. Clin Interv Aging. 2018;13:1111-1119.