Older Adults Are Not One Group: The Oldest Face the Sharpest Climate Health Risks in the Western Pacific

The oldest older adults bear a disproportionate share of the health burden from climate change across the Western Pacific Region, according to a new scoping review that synthesized 119 cases extracted from 100 peer-reviewed studies published between 2016 and 2025. The review, which followed the Joanna Briggs Institute methodology and the PRISMA-ScR checklist, is the first comprehensive attempt to map how climate-related threats affect health outcomes across different age subgroups within older populations in the region. Its central conclusion challenges a long-standing assumption in both research and policy: that everyone aged 65 and over faces roughly the same climate-related risk. In fact, the evidence points to a consistent gradient, with people generally aged 75 and above—often labeled old–old adults—showing higher point estimates of vulnerability than younger older adults in many, though not all, comparisons.

The demographic stakes in the Western Pacific are enormous. The number of people aged 60 years or over in the region is projected to double between 2020 and 2050, and WHO estimates indicate that more than 240 million people aged 65 and older currently live there. This aging trend is colliding with intensifying climate impacts, including more frequent and severe heatwaves, tropical cyclones, storms, and droughts. Older adults are physiologically more susceptible to these threats because of reduced sweating and fluid dysregulation, chronic diseases, polypharmacy that impairs thermoregulation, cognitive impairment, and social isolation. Sociodemographic inequities and ageism further increase exposure and hinder recovery, amplifying risks of heat stroke, cardiovascular events, and neurodegenerative disease.

Yet most previous research has treated older adults as a homogeneous block. The review’s authors argue that this approach can mask the specific vulnerabilities of the oldest subgroup, since young-old adults may not differ substantially from the general adult population. To address this, the team searched PubMed, Scopus, and Embase using keyword clusters for climate change, older adults, and the Western Pacific, grounded in the World Health Organization’s 2022 list of climate-related threats. That list covers extreme and prolonged heat or cold, air pollution, rising sea levels, extreme weather events, and vector-borne and zoonotic diseases, supplemented with wildfire and drought. Air pollution and vector-borne disease terms were required to co-occur with climate-related terms to keep the search relevant and manageable.

The screening process was demanding. From 544, 2440, and 491 records in the three databases respectively, the team removed 864 duplicates and excluded 2047 records at title and abstract screening. Of 564 full texts assessed, 469 were excluded—443 because they lacked subgroup analysis among older adults and 26 because they reported older-adult results in non-comparable forms, such as raw fatality counts without population denominators. Thirteen additional studies identified before the search strategy was finalized brought the total to 100 original articles. Studies were restricted to English-language, peer-reviewed research published between 2016 and 2025, and gray literature was excluded to ensure the reliability of the estimates being compared.

Geographic concentration emerged as one of the starkest patterns. Seventy of the 100 studies came from mainland China, accounting for 84 of the 119 cases, or 71 percent. Japan contributed 10 studies, Australia 8, Hong Kong Special Administrative Region 7, the Republic of Korea 2, and Malaysia and Vietnam one each, alongside one multi-country global study. No studies from Pacific island nations were identified, even though sea-level rise and vector-borne disease risk are generally more pronounced in those countries. The authors suggest this absence likely reflects limitations in data availability for age-stratified climate-health research in the region rather than a lack of exposure.

Threat coverage was similarly skewed. Extreme heat dominated the evidence base, appearing in 61 of 119 cases (51 percent), followed by extreme cold in 31 cases (26 percent), air pollution in 11 (9 percent), temperature variability in 9 (8 percent), and extreme weather in 7 (6 percent). No studies examining age-stratified impacts of rising sea levels or vector-borne disease among older adults were found. Mortality was the most commonly evaluated outcome, particularly for heat and cold, with hospital admissions, emergency service use, and other health status measures also represented.

To gauge the certainty of evidence, the reviewers classified studies into three tiers. Tier 1 studies reported subgroup estimates without formal statistical comparison; Tier 2 studies formally tested differences against a younger reference group, generally aged under 65; and Tier 3 studies compared older-adult subgroups directly or tested all subgroups simultaneously, providing the strongest evidence of a within-group age gradient. Overall, 72 of 119 cases showed vulnerability increasing with age among older adults. Extreme cold produced the most pronounced gradient: 25 of 31 cases (81 percent) showed increasing vulnerability with age, and every study that applied a formal statistical test—three Tier 3 cases and three Tier 2 cases—confirmed the pattern. In one study of ambient cold exposure, mortality risk rose across age groups, with odds ratios of 1.19 for ages 75 to 84 and 1.33 for ages 85 and over reaching significance against the under-65 reference, while the estimate for ages 65 to 74 did not. A study of cold spells found relative risks of 1.46 for ages 65 to 74 and 1.62 for ages 75 and over, with a formal test confirming a significant age gradient.

Extreme heat showed a somewhat weaker but still substantial gradient, with 39 of 61 cases (64 percent) indicating increasing vulnerability with age. Among the formal comparisons, 5 of 11 Tier 3 cases and 5 of 6 Tier 2 cases supported the pattern, and 29 of 44 Tier 1 cases showed an age gradient. Some cases found that heat significantly increased mortality among old–old but not young-old adults, and one study of compound hot-dry events found mortality effects significantly larger among old–old adults than among people under 65. Under less severe conditions where only a heatwave occurred, significantly large impacts were observed only among old–old individuals. Temperature variability showed a weaker gradient, with 3 of 9 cases (33 percent) showing increasing vulnerability, though 2 of 3 Tier 3 cases did; one study found that only adults aged 75 and over showed significant associations between diurnal temperature range and cardiovascular emergency admissions, with effects among women aged 75 and over roughly one to two times higher than among men. Air pollution was intermediate, with 4 of 11 cases (36 percent) showing the gradient, and results sometimes diverging depending on whether particulate matter was measured as PM2.5 or PM10. Extreme weather showed the least pronounced gradient of all: only one of seven cases, a flood study, showed increasing vulnerability with age, and two cases actually found young-old adults more affected—one on mental health impacts of bushfires, floods, and heatwaves, and another on nursing home admissions after flooding.

A small number of cases also reported temporal trends, which the authors caution should be interpreted as suggestive given their scarcity. These generally showed declining vulnerability to extreme cold across both age subgroups, possibly reflecting improved adaptation policies, while heat trends were mixed, with some cases showing increasing risk and others no significant change or decline. One hospital admission study found that heat-related relative risks for ages 60 to 69 and 70 to 79 shifted from non-significant over 1995 to 2016 to significant in 2016 alone, while the 80-plus group showed no significant change. The authors note that a non-significant age-related increase does not imply uniform vulnerability; the relationship may be non-monotonic, or true differences may lack statistical power, and where absolute risk among older adults is already high, relative risk measures may understate the absolute increase.

The review’s implications cut against current policy frameworks, which typically define older adults as a single category aged 60 or 65 and over. WHO regional documents and the Regional Action Plan on Healthy Aging in the Western Pacific rarely distinguish subgroups within older populations, and the authors argue this homogenization may leave the old–old inadequately protected. Their evidence suggests the age at which climate-related vulnerability becomes statistically distinguishable from younger populations often begins closer to 75, with 9 of 10 Tier 2 cases showing significant differences only among adults aged 75 and over. With the population aged 75 and above in the region projected to more than triple by 2050, and heat-related deaths among adults over 65 already reported to have increased by more than 85 percent since the 1990s, the authors recommend that researchers routinely report outcomes separately for young-old and old–old adults, and that policymakers design and monitor climate adaptation strategies with explicit attention to the oldest group. They also acknowledge limitations: the keyword-based search without citation searching may have missed eligible studies, and the concentration of evidence in mainland China and English-language literature limits generalizability across the region’s diverse settings.

Subject of Research: Age-stratified health impacts of climate change on older adults in the Western Pacific Region

Article Title: Age-stratified health impacts of climate change on older adults in the Western Pacific Region: a scoping review

Article References: Lee, D., Oh, I.-H., Ji, J. S., Kanda, M., Kimura, H., Lee, S., Mothe, J., Park, J., Shinee, E., & Kim, H. (2026). Age-stratified health impacts of climate change on older adults in the Western Pacific Region: a scoping review. The Lancet Regional Health – Western Pacific, 75, Article 102004. https://doi.org/10.1016/j.lanwpc.2026.102004

Image Credits: AI Generated

DOI: 10.1016/j.lanwpc.2026.102004

Keywords: climate change, older adults, Western Pacific Region, scoping review, extreme heat, extreme cold, population aging, air pollution, temperature variability, vulnerability, public health, old-old adults