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

From the articles that studied morbidity, outcomes such as hospitalizations, emergency department visits or hospital admissions for cardiovascular causes (hypertension, heart dis- ease, stroke, acute myocardial infarction, ischemic heart disease, cerebrovascular disease and heart failure), respiratory causes (respiratory diseases, pneumonia, chronic obstructive pulmo- nary disease (COPD) and respiratory tract infections), renal causes (acute renal injury and renal function impairment), heat-related illness, acute psychiatric causes (depression, schizo- phrenia and bipolar disorder), dementia and hip fracture were described. Interestingly, a research conducted in China from 2002 to 2018 revealed a noteworthy find- ing. According to the study, there was a reduction in the rates of heart disease, stroke, and hypertension with every 1˚C increase in average annual temperature. Specifically, the rates of heart disease decreased by 6% (OR: 0.94; 95% CI: 0.92–0.95), stroke by 5% (OR: 0.95; 95% CI: 0.94–0.97), and hypertension by 3% (OR: 0.97; 95% CI: 0.96–0.97) [39]. On the other hand, a separate study performed in China from 2009 to 2011 that also investigated changes in ambi- ent temperature and cardiovascular morbidities, reported an increased relative risk of emer- gency room admissions for cardiovascular disease when the diurnal temperature range (DTR) increased. In fact, a 1˚C increase in DTR corresponded to a 1.46% (95% CI: 0.74–2.19) and 1.13% (95% CI: 0.11–2.16) increase in all cardiovascular diseases among females (2-day lag

effect) and males (4-day lag effect), respectively [53]. Regarding respiratory morbidities, an USA study revealed that during full drought periods (at least 150 days), respiratory hospital admissions decreased by -1.99% (95% PI: -3.56,-0.38) compared to non-drought periods [38]. Another relevant finding from this article was that the risk of cardiovascular admission and all-cause mortality increased during drought periods vs non-drought periods in geographic locations experiencing less frequent droughts [38]. Thus, the negative health outcome was worse in areas where the climate change phenomenon was not frequent or common. This may be explained due to population acclimatization. In the western USA, the inhalation of fine particulate matter (PM2.5) stemming from wildfire smoke also resulted in alterations in respiratory morbidities. In women and men, the risk of respira- tory admissions rose by 10.4% and 3.7% correspondingly when comparing smoke wave days to non-smoke days [43]. Concerning renal causes, McTavish et al., studied the association between heat periods and acute kidney injury in a Northern climate—Canada. The authors found that heat periods were associated with a higher risk of acute kidney injury by 11% [44]. Elevated daily temperatures were also associated with a detrimental impact on kidney function in the population receiving anti-hypertensive medication [47]. Focusing on mental health, the findings from the case-crossover study of Qiu et al., showed an increase in relative risk of hospital admission by 3.66% (95% CI: 3.06–4.26) for depression,

3.03% (95% CI: 2.04–4.02) for schizophrenia and 3.52% (95% CI: 2.38–4.68) for bipolar disor- der for each 5˚C increase in short-term exposure to cold season temperature [46]. Dementia was another neurological disorder explored and an increase in summer mean temperature was reported as associated with a 12% (95% CI: 1.09–1.15) increase in the risk of dementia-associ- ated hospitalization. Likewise, a 0.5˚C increase in variability of summer temperature was linked to an increased risk for this condition (HR = 1.07; 95% CI: 1.05–1.09) [10]. Physical injuries were also investigated. Two distinct regions with contrasting climates in Spain were explored by Tenı´as et al. and the relationship between weather conditions and inci- dence of hip fracture was studied. Increased risk of hip fracture incidence was associated with days with more frequent and/or high-speed winds by 23.3% (95% CI 7.7–41.1) in a Mediterra- nean climate. Meanwhile, in the region characterized by an inland climate, the observed differ- ence in the incidence of hip fractures was comparatively lower and did not reach statistical significance [50]. PLOS ONE Climate change, ageing and health PLOS ONE | https://doi.org/10.1371/journal.pone.0297116 April 24, 2024 10 / 17