The world's population is aging, and that's a good thing. It reflects improvements in public health and medicine and the fact that, as a global society, we have reduced the risk of premature death and controlled or prevented disease. Look at it this way: In 1950, the likelihood of a baby born in a high-income country surviving to age 90 was 4.8%; now, it's 26.7%. It's projected to be 50% by 2060.

But is the world socially and economically prepared for a continually expanding aging population? A pioneering study by researchers from the National University of Singapore (NUS) and Columbia University in New York has revealed that some countries are more ready than others.

"While high-income countries lead the rankings in readiness for a rapidly aging society, low- and middle-income nations trail behind," said Assistant Professor Cynthia Chen from the NUS Saw Swee Hock School of Public Health (SSHSPS) and the study's lead and corresponding author. "Although low- and middle-income countries often have younger populations today, many are expected to experience rapid population aging in the future."

The researchers previously studied how high-income countries have adapted to population aging, examining five key domains in a Global Aging Society Index: productivity and engagement, well-being, equity, cohesion, and security. For the present study, they modified their Index, refining each domain and weighting it so it could be applied to low-, middle-, and high-income countries.

Here is what each of the domains refers to. The productivity and engagement domain is about facilitating the engagement of older people in society, either through paid or volunteer work. Well-being, as you'd expect, is the provision of healthcare that is informed by an understanding of the particular needs of older persons. Equity is the even distribution of resources across the older population, a lessening of the gap between the 'haves' and 'have nots'. The cohesion domain is about maintaining social connectedness and camaraderie within and between generations. And security refers to providing economic and physical security to older persons.

The researchers used their modified Index to assess the readiness of 143 countries – 95.4% of the world's population – to tackle the challenges of an aging population. Countries scored lowest in the productivity and engagement domain, followed by the equity domain, well-being domain, and security domain. The highest scores were for cohesion. In most domains, a country's gross domestic product (GDP) level was significantly associated with its aging index score.