In a study conducted at Columbia University Mailman School of Public Health and the Robert N. Butler Columbia Aging Center, researchers developed a new metric, the “Adjusted Health Dependency Ratio” (HADR) as an alternative to most commonly used metric of aging, the old age dependency ratio (OADR).
Research suggests that age-related health burden is distinct from a ratio based exclusively on age and is the first to integrate the dependence associated with poor health to generate a new metric that represents a more holistic measure dependency for 188 countries. The results are published in Lancet Healthy Longevity.
“Rather than using an arbitrary age limit such as age 65, we used absolute health,” said lead researcher Vegard Skirbekk, PhD, professor of population and family health. at Columbia University Mailman School of Public Health. “In some countries, a given level of poor health occurs in the 40s and in the 70s in others. Thousands of studies have been written using old age dependency – but they are probably invalid,” notes Skirbekk.
In the current study, Skirbekk proposes constructing a dependency metric using information from the 2019 Global Burden of Disease study as an alternative to OADR. This health-adjusted dependency ratio was generated for the adult population aged 20 and over for each country, where the numerator consists of the relatively unhealthy or “dependent” population and the denominator includes the relatively healthy people, who could potentially “sustain” the dependent population. OADR, on the other hand, is more associated with the growth of health expenditure.
The study published in Lancet Longevity shows that African countries, and some countries in Central Asia, South Asia and Eastern Europe, are older than their demographics suggest. Nations in Oceania, East Asia, Europe, North America, Central and South America are younger.
As an example, Japan had the highest OADR at 0.49 in 2017, followed by Western European countries (with OADR > 0.32). The United States, Canada, Eastern Europe, Uruguay, China, South Korea and Thailand follow with an OADR > 0.24. “This implies that several demographically older populations might have relatively lower HADR burden if health levels are good, while demographically younger populations might have higher HADR if health levels are poor.
In terms of health, the proportion of elderly people is about the same for rich and poor countries. “This is important, because it means the world is just as old – or young – and similar types of health problems apply. It also means that the delivery of health care needs to be reoriented towards treating the life-course-related diseases, Skirbekk observed. “And finally, being young demographically is no guarantee of being young as a nation; in many cases the opposite is true.”
Past assessments were made up of measures that tended to be based on data for a single country – mostly populations of European ancestry. “In sum, measures of early aging tend to lack global coverage, global demographic information, or global health data,” noted Skirbekk, who also works at the Columbia Butler Aging Center.
“In fact, while the old-age dependency ratio or OADR was often used as an indicator of population aging, it did not take into account variation in health and therefore may represent an incomplete assessment of aging and dependency. related to aging,” Skirbekk said. “Traditional indices used on variation in aging at the population level tended to focus only on demographic indicators. Our method allowed us to generate a new metric to measure aging, allowing us to assess the variation in both population aging and age-specific health across countries.
Skirbekk further points out that previous research has shown that in 2017, the chronological age at which this occurs differs by up to thirty years, ranging from 45.6 years in Papua New Guinea to 76.1 years in Japan.
“In the future, it may be more useful to more holistically assess addiction and policies associated with age-related addiction using a metric that includes the impacts of poor health, such as HADR,” Skirbekk said. “The results of our work have specific policy implications that will help countries plan, develop and implement aging policy programs and health care reforms to effectively address the rapid demographic change underway.”