Is climate change turning up the heat on China's aging population?

By Dr. Priyom Bose, Ph.D.Oct 2 2023Reviewed by Benedette Cuffari, M.Sc.

The rapid aging of the global population is expected to become a significant social problem in the future. A recent Npj Climate and Atmospheric Science study investigates the role of temperature rise on mortality rates in the elderly population in China.

Study: Projection of temperature-related mortality among the elderly under advanced aging and climate change scenario. Image Credit: Ljupco Smokovski / Shutterstock.com

Background

Two of the most interlinked concerns of the 21^st century are population aging and rapid climate change. Climate change contributes to rising global temperatures, which has been correlated with higher morbidity and mortality rates. Climate change also leads to biodiversity and ecosystem changes that can have immediate or delayed impacts on human health.

Previous studies on temperature-related mortality due to climate change have shown that the risks imposed by cold and hot temperatures are not the same in relation to age. For example, compared to higher temperatures, low temperature causes more global non-communicable deaths.

A recent survey revealed that as compared to heart-related issues, a more significant number of older individuals died due to cold-associated conditions. These findings imply the importance of mitigating the effect of cold temperatures on advanced aging to combat potential severe public health consequences.

Aging has accelerated due to increased life expectancy and reduced fertility rates. The United Nations World Population Outlook 2022 reported that the proportion of the elderly population will globally increase by 60% from 2022 to 2050.

According to a 2021 analysis, the aging rate of the Chinese population has increased by 14%, which is expected to further increase to 21% by 2025. This increase in the aging rate of China’s elderly population will likely continue until 2055 and then stabilize. Due to increasing life expectancy, advanced aging could become a significant issue in China, particularly in the second half of the 21^st century.

An increase in the number of heat-related deaths has been documented in China and is expected to continue to rise due to global warming. Although many studies have investigated the effects of climate on mortality rates, these studies have not considered individuals over 80 or 90 years of age, many of whom are most affected by non-optimal temperatures.

About the study

The current study analyzed the direct and indirect effects of temperature on the oldest group in China. This study considered population data from Nantong City, China, as it has the highest proportion of older people among 340 cities.

To determine how temperature change affects this population, all-cause mortality and temperature/humidity data were collected between January 1, 2012, and December 31, 2017. This data was categorized into three groups based on age, including 65-79 years (young-old), 80-89 years (middle-old), and 90+ years (oldest-old).

The effect of temperature on the aging population was determined using 27 global climate models that are included in the Coupled Model Intercomparison Project Phase 6 (CMIP6) and four emission scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5).

Study findings

The minimum mortality temperature (MMT) for the elderly population in Nantong increased with age, which suggests that climate change and aging increase heat-related mortality and reverse the trend of cold-related mortality. 

Based on the assumption that the population demographics of Nantong remained constant, the study findings indicate that climate change, which is defined as an increase in extremely high temperatures (high RR) and a decrease in moderately low temperatures (low RR), will continue to cause an increase in mortality. Thus, future studies must assess whether climate change will influence positive or negative net annual mortality related to temperature.

Consistent with previous reports, the study findings reveal that the range of high temperatures was narrower compared to low temperatures. Furthermore, most of the minimum temperature-related mortality was associated with the local temperature percentile.

Typically, the association between temperature and mortality is dependent on numerous social factors, including urbanization rate, the region’s development, usage of air conditioning, central heating, economic performance, and population age structure. 

The population-attributable fraction (PAF) of cold and heat varied across different populations and climate change scenarios. The interactive effect of advanced age and increased temperature was even higher than the accumulation of their independent effects.

Since cold-related mortality linked to advanced aging will continue to increase or remain constant, health risks associated with low temperatures must also be considered.

Conclusions

Advanced aging accelerates heat-related mortality; therefore, governments throughout the world must focus on reducing greenhouse gas emissions to mitigate global warming, which will reduce heat-related mortality in the oldest old age group. The study findings emphasize the importance of formulating both cold and heat prevention policies based on local population structure and the extent of climate change.