Healthcare usually focuses on treating the diseases and symptoms presented by patients. The World Health Organization (WHO) wants to promote research on 'Healthy Aging'. To this end, they have proposed the 'intrinsic capacity' (IC) construct: a composite of five different physical and mental capacities of an individual. Together with environmental factors, the IC determines a person's 'functional ability'. "Functional ability is about a person's well-being and quality of life. This would involve questions such as: can you do basic daily activities? Can you maintain relationships? Can you contribute to society?" says researcher Natasja van Schoor.
The researchers suggest that an IC score can be calculated by choosing one or more measurement instruments for the five domains of intrinsic capacity: mobility, cognition, vitality, psychology and senses. The results of these measurements are then rescaled to a score from 0 to 100 in order to calculate an average of these scores. To test whether such a calculation works, they used data from LASA: a study in which older people are interviewed and tested over a long period of time. From the LASA study, the researchers took data from 1908 participants aged between 57 and 88 years. They looked at how large the difference was in IC scores between younger and older people and between people with different numbers of chronic diseases. They also looked at whether such a score could predict the risk that a person's ability to do daily activities would deteriorate, or the risk of dying within 10 years.
In the end, the score could show a difference between people with younger or older age and better or worse health status. Scores were higher among younger participants and those who had fewer chronic diseases. One extra point in the IC score gives a person a 7% lower risk to be functionally impaired after 6 years, and 2% lower risk to die within 10 years.
With the IC-score, the researchers started a new study in June 2023 to investigate how the intrinsic capacity of older people changes during ageing. They will also investigate what role environmental factors play, and also what the wishes and needs of older adults themselves are during ageing. Van Schoor: "We have now measured intrinsic capacity at one time point, the next step is to examine how the IC score changes during ageing. This is important because WHO recommends monitoring the IC of older adults, in order to intervene early in time in case of a sudden decline. We also plan to use machine learning to look at predictor variables of functional ability, such as environmental variables but also diseases and lifestyle, to see which ones are most important to include in the Healthy Aging model of the WHO.
