Intrinsic capacity scores predict the risk of mild cognitive impairment in older adults

A recent study published in the journal GeroScience suggests that a person’s overall physical and mental reserve can predict their risk of experiencing memory and thinking problems later in life. Scientists found that older adults with a lower baseline of physical and psychological abilities have a higher chance of developing mild cognitive impairment within a few years. These findings suggest that taking a broad approach to health as we age provides evidence for better strategies to protect our brains.

The World Health Organization defines intrinsic capacity as the total combination of physical and mental abilities an individual can rely on. This idea focuses on a person’s existing strengths rather than their diseases or deficits. The concept promotes a holistic view of aging that includes movement, emotional wellbeing, senses, vitality, and thinking skills.

Traditionally, medicine has often looked at aging simply as the presence or absence of specific diseases. The concept of intrinsic capacity shifts that perspective toward a broader understanding of overall functioning. Measuring these combined strengths provides a complete picture of an individual’s resilience.

Previous evidence shows that having a high intrinsic capacity tends to reduce the risk of hospital visits. It also helps older adults maintain their daily independence for much longer periods. Yet, scientists had not previously tested whether this combined measure of health could predict the onset of memory and thinking problems.

The researchers conducted this study to see if a person’s intrinsic capacity could indicate their future risk of cognitive decline. They wanted to understand if everyday physical and mental abilities could serve as early warning signs. Identifying these early patterns could lead to better public health strategies for an aging population.

“Given my interest in brain health and ageing, I thought it could be important to address the relationships between cognition and this relatively novel concept of intrinsic capacity. I designed this study primarily as research project for an honours medical student, but given the interesting results I decided to expand the analyses for publication,” explained study author Ingrid Buller-Peralta, an honorary fellow at the Centre for Clinical Brain Sciences at the University of Edinburgh.

The scientists analyzed data from the English Longitudinal Study of Ageing. This is a large, ongoing project that tracks the health and wellbeing of older adults living in the United Kingdom. The researchers focused on an exact sample of 731 older adults between the ages of 60 and 89.

At the start of the analysis, none of these individuals had been diagnosed with dementia or Alzheimer’s disease. They all had normal memory and thinking skills during their initial assessment. The scientists measured the participants’ intrinsic capacity using data collected between 2012 and 2013.

The researchers looked at twelve specific indicators spread across five broad categories of health. These categories included thinking skills, movement, emotional health, sensory abilities, and general physical vitality. To measure basic thinking skills, they tested the participants on their memory recall and their awareness of the current date and time.

To measure movement, the researchers recorded walking speed, standing balance, and the time it took to repeatedly stand up from a chair. Emotional health was measured by asking participants about their sleep quality, symptoms of depression, and overall life satisfaction. Sensory abilities included self-reported questionnaires about vision and hearing quality.

Vitality was assessed through lung capacity tests and hand grip strength using specialized medical equipment. The scientists combined all these separate measurements into a single overall score for each person. To do this, they used a mathematical method called item response theory, which calculates an underlying trait based on performance across different tests.

Four to five years later, the researchers evaluated the participants’ thinking and memory skills again. They used a standard screening tool called the Mini-Mental State Examination. This test asks thirty questions to check basic mental functions like memory, attention, and language.

Based on these test scores, the older adults were grouped into categories of normal cognition, mild impairment, or moderate to severe impairment. The researchers found that a lower intrinsic capacity score was associated with a significantly higher risk of developing mild cognitive impairment later on. Participants who maintained normal cognitive abilities over the years had significantly higher initial scores than those who developed cognitive issues.

Older age and lower levels of education also predicted a higher likelihood of memory and thinking problems. The scientists adjusted their data to account for lifestyle factors like physical activity and the number of existing health conditions. In this adjusted model, a person’s sex, exercise habits, and chronic diseases did not independently predict later cognitive decline.

The lack of an independent link between existing diseases and later memory issues suggests that intrinsic capacity captures a more accurate picture of aging. The scientists did note that individuals with a history of smoking showed a higher risk for mild cognitive impairment. This provides evidence that smoking might harm brain health regardless of a person’s overall physical and mental baseline.

“Intrinsic capacity is a novel concept proposed by the World Health Organization that goes beyond purely physical, mental or cognitive health, but integrates several domains to reflect general wellbeing in a more holistic way,” Buller-Peralta told PsyPost. “I see it as quantifiable summary reflecting how well am I emotionally, physically and mentally, but more importantly, as the sum of all my ‘capacities’ saved like our pension funds to help us age better.”

“Although low intrinsic capacity has been related to several age-related physical declines, our study shows for the first time that it is associated with a later cognitive decline. Likewise, high IC in cognitively healthy older adults helps maintaining normal cognitive function 4-5 years later.”

“Overall, these results suggest that keeping a healthy brain a we age goes beyond focusing on one particular aspect of wellbeing such us engaging in physical or social activities, or practice a good sleep hygiene,” she explained.

The researchers pointed out a few potential misinterpretations and limitations of their work. They emphasized that statistical associations do not prove direct cause and effect between intrinsic capacity and cognitive decline. The findings simply highlight a strong predictive relationship that warrants more exploration.

The study also focused on a specific group of older adults in the United Kingdom, meaning these patterns might look different in other cultures. Future studies are needed to see if these findings replicate in populations facing different environmental stressors. Factors like extreme poverty or high air pollution could potentially influence how physical capacities relate to brain health.

Another limitation involves the use of self-reported surveys to measure things like sleep and sensory abilities. People can sometimes misremember or inaccurately estimate their own habits. The researchers suggest that future studies should use objective tools, like wearable sleep trackers, to gather more precise data.

Despite these limitations, intrinsic capacity appears to be a highly personalized way to monitor the aging process. Expanding this research could eventually help doctors use overall capacity scores as a standard screening tool in clinics. Catching early declines across multiple physical systems might allow medical professionals to intervene before memory problems become severe.

The study, “Low intrinsic capacity is associated with risk of developing mild cognitive impairment in the English Longitudinal Study of Ageing (ELSA),” was authored by Rosa Birchenough, Ingrid Buller-Peralta, Alejandra Marroig, and Graciela Muniz-Terrera.