Epidemiological transitions in Pacific Island countries and territories: 1950-2023

For decades, scientists have tracked how human populations change as they become healthier and live longer. This process, often called the epidemiological transition, describes a shift where people die less from infections, hunger, and childbirth complications, and more from long-term conditions like heart disease and diabetes. It is a story of progress, but also of complexity. Just because a country's average life expectancy goes up does not mean everyone is living the same way. A population might reach a high life expectancy by saving many children, while another reaches the same number by keeping older adults alive, even if those older adults spend their final years in poor health. Understanding exactly where a population stands in this journey—and how fast it is moving—requires looking beyond simple averages to see the specific ages, diseases, and risks that shape daily life.

A new study by Yohannes Kinfu brings this detailed perspective to the Pacific Islands, a region often overlooked in global health research due to its many small, scattered populations. By analyzing data from 1950 to 2023 across all 18 Pacific Island countries and territories, the research reveals that while these nations have made significant gains in how long people live, they are moving through this transition more slowly than the rest of the world. More importantly, the study shows that the path to longevity in the Pacific is not a single, straight line. Instead, it is a patchwork of four different health challenges happening at the same time within the same countries: saving babies, protecting young people from injury, fighting heart disease in working-age adults, and managing the frailty of old age.

The researchers began by looking at the big picture of life expectancy in the Pacific. From 1950 to 2023, the average life expectancy in the region rose from 52.8 years to 69.1 years. This is a substantial improvement, but when the scientists compared the speed of this progress to other countries with similar economic and social conditions, a gap appeared. Pacific populations improved their life expectancy by about 0.14 years less per year than their global counterparts. This slowdown was not limited to a few struggling nations; it was a regional pattern shared by all 18 countries and territories studied. The gap was widest in places like Nauru, the Solomon Islands, Tuvalu, and the Marshall Islands, where life expectancy remains furthest behind global benchmarks.

What makes this finding particularly significant is how the researchers separated two different factors: where a country is in its health journey, and when it is traveling that path. They found that the pace of improvement depends on both. Early in the transition, when life expectancy is low, gains come quickly as infant and child deaths are prevented. As a population gets healthier and life expectancy rises, the speed of improvement naturally slows down. However, the study showed that Pacific nations are slower than expected even when accounting for this natural slowing. Furthermore, the timing matters. The same level of health achieved in the 1970s saw faster progress than the same level achieved in the 2000s. This suggests that historical context, such as global health initiatives or economic shifts, plays a crucial role in how fast a population can improve.

The study also peeled back the layers of age to see where the gains and losses are actually happening. In the early decades of the study, the biggest improvements came from saving young children. As time went on, the focus of progress shifted. By the most recent years, the biggest driver of life expectancy gains was no longer saving babies, but keeping adults alive. Yet, a troubling trend has emerged in the middle years of life, specifically between ages 25 and 69. In many Pacific nations, this age group is now the bottleneck. While deaths in childhood have continued to fall, deaths among working-age adults have stagnated or even increased in some places. This is largely due to a rise in heart disease, diabetes, and kidney problems. In fact, for several countries, the negative impact of these diseases on life expectancy has completely offset the gains made in other age groups.

This shift is reflected in the changing causes of death. In 1990, the leading causes of death were a mix of infections, maternal issues, and injuries. By 2023, the landscape had changed dramatically. Heart disease had become the leading cause of death across almost all the islands, followed closely by diabetes and stroke. The risks driving these deaths have also converged. High blood pressure, high blood sugar, and obesity are now the top health risks across the region. There is one notable exception: in Papua New Guinea and the Solomon Islands, air pollution remains a leading risk factor, showing that environmental challenges still play a major role in some parts of the Pacific.

The research also looked at what it means to be "healthy" versus just being alive. The scientists divided potential life into years spent in good health, years lost to early death, and years lost to living with illness. They found that while people are living longer, they are not necessarily living healthier lives. In the youngest age groups, most of the remaining health loss is due to illness rather than death. For young people, the nature of the threat has changed; self-harm and injuries have replaced infectious diseases as the leading causes of death in many places. For adults, the burden is a mix of premature death and chronic illness. The most striking finding is that for people aged 25 to 69, the loss of healthy years is now dominated by morbidity—living with disease—rather than by dying young. This means that even if people survive longer, they may spend a significant portion of their working lives managing chronic conditions.

The study concludes that the Pacific experience cannot be understood by looking at a single number like life expectancy. Instead, it is defined by four overlapping health transitions that coexist within the same countries. There is an early survival transition focused on saving infants, a youth health transition dealing with injuries and mental health, a premature cardiometabolic transition where heart disease and diabetes threaten working-age adults, and an advanced ageing transition focused on dementia and frailty. These four stages are not sequential steps that a country finishes one by one; they are happening simultaneously. A single nation might be successfully saving babies while struggling to control diabetes in its middle-aged population.

This complexity has important implications for how health systems should respond. A one-size-fits-all approach will not work. The findings suggest that Pacific nations need tailored strategies that address the specific challenges of each life stage. This means continuing to invest in maternal and child health, but also urgently addressing the rising tide of heart disease and diabetes among adults. It also means recognizing that simply extending life is not enough; the goal must be to extend healthy, disease-free years. The study highlights that while the Pacific has made remarkable progress in the last 70 years, the path forward requires a more nuanced understanding of where the region stands, not just in terms of how long people live, but how they live.