● Varied factors lead to uneven climate health outcomes were revealed.

Climate change significantly impacts human health, exacerbating existing health inequalities and creating new ones. This study addresses the lack of systematic review in this area by analyzing 2440 publications, focusing on four key terms: health, disparities, environmental factors, and climate change. Strict inclusion criteria limited the selection to English-language, peer-reviewed articles related to climate health hazards, ensuring the relevance and rigor of the synthesized studies. This process synthesized 65 relevant studies. Our investigation revealed that recent research, predominantly from developed countries, has broadened its scope beyond temperature-related impacts to encompass diverse climate hazards, including droughts, extreme weather, floods, mental health issues, and the intersecting effects of Coronavirus Disease 2019. Research has highlighted exposure as the most studied element in the causal chain of climate change-related health inequalities, followed by adaptive capability and inherent sensitivity. The most significant vulnerabilities were observed among populations with low socioeconomic status, ethnic minorities, and women. The study further reveals research biases and methodological limitations, such as the paucity of attention to underdeveloped regions, a narrow focus on non-temperature-related hazards, challenges in attributing climate change effects, and a deficit of large-scale empirical studies. The findings call for more innovative research approaches and a holistic integration of physical, socio-political, and economic dimensions to enrich climate-health discourse and inform equitable policy-making.

● Temperature variability is an independent risk factor of cardiovascular diseases.

Relationships between nonoptimal temperatures and cardiovascular disease (CVD) mortality have been well documented. However, evidence of the association between temperature variability (TV) and CVD morbidity is limited. This study aimed to quantify the risk and burden of CVD-related hospitalization associated with the magnitude and direction of TV. Data on meteorology and population-based hospitalizations for myocardial infarction (MI) and stroke were collected in Guangzhou, China, from 2013 to 2017. Hourly temperature variability (HTV) was measured as the standard deviation of hourly temperature records over specific exposure days. The direction (upward or downward) of HTV was defined as the average daily mean temperature change relative to that of the previous day during the exposure period. Quasi-Poisson regression was applied to assess the impact of HTV after adjusting for the daily mean temperature, and the hospitalization fractions attributable to HTV were calculated. A 1 °C-increase in HTV was significantly associated with a 2.24% and 1.72% increase in hospitalizations for MI and hemorrhagic stroke (HS) at lag 0–1 d, respectively, and a 1.55% increase in hospitalizations for ischemic stroke (IS) at lag 0–3 d. During the study period, 5.99%, 4.64%, and 4.53% of MI, HS, and IS hospitalizations, respectively, were attributable to HTV. The upward TV exerts acute effects on CVD hospital admissions, whereas the impact of downward TV generally lags. These findings highlight the importance of the magnitude and direction of temperature fluctuations, in addition to the mean level, in assessing the adverse health impacts of temperature variations.

● Designing of flood passages toward inundation risk reduction was summarized.

Urban roads can be designated as surface flood passages to transport excess runoff during extreme storms, thereby preventing local flooding, which is known as the major drainage system. However, this practice poses significant risks, including human loss and property damage, due to the high flow rate and velocity carried by roads. Moreover, urban roads with low flood-resilience may significantly hamper the transportation function during severe storms, leading to dysfunction of the city. Therefore, there is an urgent need to transform risk-oriented flood passages into resilient urban road-based flood passages. This paper presents a systematic review of existing methodologies in designing a road network-based flood passage system, along with the discussion of new technologies to enhance system resilience. The study also addresses current knowledge gaps and future directions. The results indicate that flood management measures based on the urban road network should integrate accessibility assessment, lifeline and emergency planning to ensure human well-being outcomes. Furthermore, the special needs and features of vulnerable groups must be taken into serious consideration during the planning stage. In addition, a data-driven approach is recommended to facilitate real-time management and evaluate future works.

● The effect modifications of urban landscape were explored at the intra-urban level.

Despite increased attention given to potential modifiers of temperature-mortality associations, evidence for variations between different urban landscape characteristics remains limited. It is in this context that in this paper effect modifications of multiple urban landscape characteristics are explored under different heatwave definitions for different age groups and gender in Hong Kong, China. Daily meteorological data and heatwave-related mortality counts from 2008 to 2017 were collected from the Hong Kong Census and Statistics Department, China. A case-only design was adopted, combined with logistic regression models to examine the modification effects of five urban landscape characteristics under six heatwave definitions. Stratified analyses were conducted to investigate age- and gender-specific effect modifications. It is found that individuals living in greener areas experienced lower levels of mortality during or immediately after heatwaves. In contrast, a higher building density and nighttime land surface temperature (LST) were associated with a higher heatwave-related mortality risk. Pronounced effect modifications of these urban landscape characteristics were observed under hotter and longer heatwaves, and in older adults (age ≥ 65 years) and males. The findings provide a scientific basis for policymakers and practitioners when considering measures for coping with hotter, longer, and more frequent heatwaves in the context of global climate change.

● A study assessing the temperature-injury relationship was conducted among students.

Although studies have suggested that non-optimal temperatures may increase the risk of injury, epidemiological studies focusing on the association between temperature and non-fatal injury among children and adolescents are limited. Therefore, we investigated the short-term effect of ambient temperature on non-fatal falls and road traffic injuries (RTIs) among students across Jiangsu Province, China. Meteorological data and records of non-fatal outdoor injuries due to falls and RTIs among students aged 6–17 were collected during 2018–2020. We performed a time-stratified case-crossover analysis with a distributed lag nonlinear model to examine the effect of ambient temperature on the risk of injury. Individual meteorological exposure was estimated based on the address of the selected school. We also performed stratified analyses by sex, age, and area. A total of 57322 and 5455 cases of falls and RTIs were collected, respectively. We observed inverted U-shaped curves for temperature-injury associations, with maximum risk temperatures at 18 °C (48th of daily mean temperature distribution) for falls and 22 °C (67th of daily mean temperature distribution) for RTIs. The corresponding odds ratios (95% confidence intervals) were 2.193 (2.011, 2.391) and 3.038 (1.988, 4.644) for falls and RTIs, respectively. Notably, there was a significant age-dependent trend in which the temperature effect on falls was greater in older students (P-trend < 0.05). This study suggests a significant association between ambient temperature and students’ outdoor falls and RTIs. Our findings may help advance tailored strategies to reduce the incidence of outdoor falls and RTIs in children and adolescents.

● Four scenarios were used to project heat-related excess mortality in China.

Climate change is one of the biggest health threats of the 21st century. Although China is the biggest developing country, with a large population and different climate types, its projections of large-scale heat-related excess mortality remain understudied. In particular, the effects of climate change on aging populations have not been well studied, and may result in significantly underestimation of heat effects. In this study, we took four climate change scenarios of Tier-1 in CMIP6, which were combinations of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the exposure-response functions derived from previous studies combined with baseline age-specific non-accidental mortality rates to project heat-related excess mortality. Then, we employed the Logarithmic Mean Divisia Index (LMDI) method to decompose the impacts of climate change, population growth, and aging on heat-related excess mortality. Finally, we multiplied the heat-related Years of Life Lost (YLL) with the Value of a Statistical Life Year (VSLY) to quantify the economic burden of premature mortality. We found that the heat-related excess mortality would be concentrated in central China and in the densely populated south-eastern coastal regions. When aging is considered, heat-related excess mortality will become 2.8–6.7 times than that without considering aging in 2081–2100 under different scenarios. The contribution analysis showed that the effect of aging on heat-related deaths would be much higher than that of climate change. Our findings highlighted that aging would lead to a severe increase of heat-related deaths and suggesting that regional-specific policies should be formulated in response to heat-related risks.

● Monthly hospitalization expenses are sensitive to increases in PM_2.5 exposure.

Air pollution has been a severe issue in China. Exposure to PM_2.5 has adverse health effects and causes economic losses. This study investigated the economic impact of exposure to PM_2.5 pollution using monthly city-level data covering 88.5 million urban employees in 2016 and 2017. This study mainly focused on three expenditure indicators to measure the economic impact considering lower respiratory infections (LRIs), coronary heart disease (CHD), and stroke. The results show that a 10 µg/m³ increase in PM_2.5 would cause total monthly expenses of LRIs, CHD, and stroke to increase by 0.226%, 0.237%, and 0.374%, respectively. We also found that LRI, CHD, and stroke hospital admissions increased significantly by 10%, 8.42%, and 5.64%, respectively. Furthermore, the total hospital stays of LRIs, CHDs, and strokes increased by 2.49%, 2. 51%, and 1.64%, respectively. Our findings also suggest heterogeneous impacts of PM_2.5 exposures by sex and across regions, but no statistical evidence shows significant differences between the older and younger adult subgroups. Our results provide several policy implications for reducing unequal public health expenditures in overpolluted countries.

● The main and added effect from heat co-existed in China.

Increases in ambient temperatures and the frequency of extreme heat events constitute important burdens on global public health. However, evidence on their effects on public health is limited and inconclusive in China. In this study, data on daily deaths recorded in 33 Chinese cities from 2007 to 2013 was used to evaluate the effect of heat on mortality in China. In addition to the definition of a heatwave established by the China Meteorological Administration, we combined four city-specific relative thresholds (90th, 92.5th, 95th, and 97.5th percentiles) of the daily mean temperature during the study period and three durations of ≥ 2, ≥ 3, and ≥ 4 days, from which 13 heatwave definitions were developed. Then, we estimated the main and added effects of heat at the city level using a quasi-Poisson generalized additive model combined with a distributed lag nonlinear model. Next, the estimates for the effects were pooled at the national level using a multivariable meta-analysis. Subgroup analysis was performed according to sex, age, educational attainment, and spatially stratified heterogeneity. The results showed that the mortality risk increased from 22.3% to 37.1% due to the effects of the different heatwave definitions. The added effects were much lower, with the highest increase of 3.9% (95% CI: 1.7%–6.1%) in mortality risk. Females, the elderly, populations with low educational levels, and populations living inland in China were found to be the most vulnerable to the detrimental effects of heat. These findings have important implications for the improvement of early warning systems for heatwaves.