The interplay between climate change and ageing: A systematic review of health indicators

in this systematic review growing evidence that climate change is largely affecting the physical and mental health of older adults (65 years or over). Based on the existing literature, climate change embraces different manifestations such as climate variability and its frequency and extreme events. Alterations in temperature, heat- waves, precipitation, ENSO and other modes of variability, wildfires, droughts, hurricanes, and floods were already observed and are expected to be aggravated in the future [56, 57]. The present systematic review, covering 19 original studies, revealed that the majority of these cli- mate change phenomena are associated with an increased risk of all-cause and cause-specific mortality and several morbidity outcomes in older adults. The impact on morbidity had sev- eral causes, the most common causes of hospitalization were cardiovascular or respiratory dis- ease. Climate changes affect the health of older adults directly through ambient temperature variability, extreme and abnormal temperatures, strong winds, sea temperature variability, extreme ENSO conditions and droughts, and indirectly by air pollution from wildfires. In par- ticular, full drought periods, extreme heat, smoke waves resulting from wildfires, and varia- tions in temperature within a season have an impact on respiratory morbidities. The increase in average annual temperatures, variability in sea surface temperatures, and an overall rise in daily temperatures influence cardiovascular morbidities. Renal morbidities are affected by

extreme heat, periods of high temperature, and elevated daily temperatures. Mental health is influenced by temperature increases and variability during summer and winter. Lastly, physi- cal injuries are linked to sudden variations in wind speed or direction. The higher vulnerability of the older population to heat or cold exposure and other weather events can be attributed to the physiological and pathological changes of age. Aging is associ- ated with impaired thermoregulatory control, which includes a decrease in the capacity to pro- duce sweat, the primary mechanism for heat loss. In fact, older adults experience a progressive variability in body temperature, rendering them less adept at adapting to fluctuations in exter- nal temperatures [58]. Aging also compromises the flexibility of the immune system, thus older adults are less responsive to environmental stressors [59]. Renal function impairment is likewise associated with age, as the kidney goes under age-related anatomic and functional changes, such as decreased renal blood flow. Under environmental stress, the aged kidney requires more time to respond to and correct the abnormality [60]. Finally, the presence of multiple comorbidities that may implicate excessive polypharmacy, the reduction of mobility, cognitive limitations and the presence of frailty exacerbate this vulnerability. Social factors, e.g. limited access to care, living alone and isolated and housing without air conditioning systems, can also be implicated [61].

It was possible to observe different effects of climate change phenomena between gender in several health outcomes found. Biological differences and care-seeking behaviours can partly explain these differences. For instance, women may face a greater vulnerability compared to men due to their higher subcutaneous fat and surface-to-mass ratio [62]. Women are also reported to visit care providers for both physical and mental health concerns to a greater extent than men [63]. In addition to examining gender disparities, numerous studies investigate the impact of varying income and education levels on the effects of climate change. Lower socio- economic status or poverty can exacerbate the consequences of climate change, primarily due to limited access to essential resources such as air conditioning, ventilation systems, and ade- quate home insulation necessary for maintaining optimal or safe body temperatures. More- over, individuals in lower socioeconomic groups may also face additional challenges associated with other health conditions and reduced access to healthcare services. Lower levels of education and income can lead to misinformation and less preventive and/or protective behaviours [64]. Therefore, the less educated and the ones with low socioeconomic status among the older adults are more vulnerable to a changing climate. PLOS ONE Climate change, ageing and health PLOS ONE | https://doi.org/10.1371/journal.pone.0297116 April 24, 2024 12 / 17