15 Apr 2024

NZ bucked life expectancy trend during Covid-19 paper shows: What you need to know

11:21 am on 15 April 2024
Line drawing of NZ, scientists, test tubes, and abstract shapes

Photo: RNZ

Explainer - The first two years of the Covid-19 pandemic undid earlier success in increasing life expectancy, except for in a handful of countries - Aotearoa New Zealand among them.

Global life expectancy declined by 1.6 years between 2019 and 2021, reversing the longstanding trend of life expectancy improvement, according to the latest analysis of the Global Burden of Disease study, known as the largest and most comprehensive effort to quantify health loss across places and time.

Coordinated by researchers at the Institute for Health Metrics and Evaluation at the University of Washington and published in The Lancet on 11 March, it tracked trends in excess mortality and life expectancy within and between more than 200 countries and territories.

But for seven of those - New Zealand, Taiwan, Mongolia, Japan, Iceland, Antigua and Barbuda, and Barbados - the all-age excess mortality rate for 2020 and 2021 combined was negative. That meant the locations experienced fewer deaths during the first two years of the pandemic than expected based on past trends.

"In 2020, 20 countries and territories had negative excess mortality, while in 2021, only New Zealand and Barbados had negative excess mortality."

Top-line findings

"For adults worldwide, the Covid pandemic has had a more profound impact than any event seen in half a century, including conflicts and natural disasters," author Dr Austin Schumacher, an assistant professor of health metrics sciences at the institute, said in a statement.

The paper reported the pandemic killed nearly 16 million people worldwide in 2020 and 2021, accounting for about 12 percent of deaths from all causes.

Between 1950 and 2021, global life expectancy at birth increased by 22.7 years, from 49 years to 71.7. But in the period between 2019 and 2021, it declined by 1.6 years.

During the same period, long-term trends of decreasing mortality were superseded by marked increases in mortality rates in age groups older than 15 (22 percent for men and 17 percent for women).

However, mortality in children under 5 years was largely unaffected by the pandemic and continued to decrease (by 7 percent).

What's excess mortality?

Excess mortality due to the pandemic was defined as the "net difference between the number of deaths that occurred between 2020 and 2021 and the number of deaths that would be expected over the same period based on previous trends in all-cause mortality".

In other words, the total number of deaths minus the number of expected deaths based on historical trends.

Globally comparable measures of excess mortality due to the pandemic showed substantial variation in the burden experienced by different countries and territories, the authors wrote.

New Zealand context

"These findings provide further evidence supporting the effectiveness of the elimination strategy for minimising mortality from the pandemic," Otago University epidemiologist Professor Michael Baker told RNZ.

New Zealand has been praised for its elimination strategy in the early stages of the pandemic. It kept Covid numbers down until vaccines became widely available.

New Zealand in 2020 and 2021 also experienced very little influenza.

By the end of 2021, 90 percent of the eligible population had been double vaccinated.

It was not until 2022, after the government had relaxed pandemic controls, that the country had its first major outbreak, fueled by the highly transmissible Omicron variant.

In 2022, deaths in New Zealand were up 10.4 percent on the previous year - the biggest annual increase since 1918 (following the influenza pandemic).

There were two obvious contributors to the increase: the pandemic and the country's ageing population, according to Statistics New Zealand.

In total, nearly 6000 New Zealanders have died with Covid, according to the latest Te Whatu Ora data.

But compared with other nations, New Zealand is said to have got off lightly.

"[The paper] reinforces other evidence that New Zealand's response was extremely effective at minimising mortality during the pandemic," Baker said.

The country's Covid mortality rates were still "among the lowest in the world".

"But it's a point in time, so it's limited in what it's telling us about our current experience. We're still in a prolonged pandemic mainly becuase the virus keeps changing.

"We'll have to wait at least another year for the next update, which will include the period we were heavily exposed to the virus."

The findings were also reassuring of the safety of vaccines, he added. "By far the largest number of Covid-19 vaccines were given in 2021, which was a year when excess mortality dropped to low levels."

What's missing

While the study highlighted the impact of Covid on global mortality rates, it did not address the impact of debilitating, chronic symptoms some people experience after a Covid infection.

Around 7 percent of adults in the United States say they are currently experiencing long Covid, according to the Centers for Disease Control and Prevention.

Authors of a March briefing published by the Public Health Communication Centre Aotearoa described Long Covid as "a major threat to individual health, societal wellbeing and economic performance" and called for government action to manage it.

"Long Covid is now where the pandemic is at," Baker said.

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