Gender inequalities in heat-related mortality in the Czech Republic

The differential effect of ambient temperature on age-specific and sex-specific mortality in the 300 largest cities of Russia, 2000-19: a first national time-series study

BACKGROUND

Despite a substantial body of evidence on the association between ambient temperature and mortality worldwide, there has not yet been a comprehensive country-wide assessment of the health effects of temperature in Russia. Moreover, there is no consensus on the effect of non-optimal temperatures on age-specific and sex-specific mortality. Our study aimed to provide the first analysis of temperature-related mortality in a large assembly of cities located in different geographical and socioeconomic zones of Russia.

METHODS

We analysed 19 044 538 non-accidental deaths in the 300 most populated cities in Russia between 2000 and 2019. A two-stage analysis strategy was used. First, a quasi-Poisson time-series model with distributed lag non-linear model was fitted to estimate city-specific associations. Second, these associations were pooled with multivariate multilevel meta-regression, from which we also calculated temperature-attributable mortality.

FINDINGS

Relative risks were generally higher for cold than for heat, except for cities in southern European Russia. Cold had a similar effect in both sexes, with a varying age gradient across cities. Although the effect of heat was generally stronger in women than in men, with the relative risk increasing steadily with age in both sexes, men younger than 60 years had a significantly higher risk of dying from heat than women of the same age. With a total of 106 007 (95% empirical CI [eCI]: 88 942-121 318) temperature-attributable deaths, there was a higher mortality attributable fraction for cold (10·74%, 95% eCI 8·80-11·99) than for heat (0·67%, 0·42-0·88).

INTERPRETATION

Russia has a high temperature-related mortality burden, with large differences in risk between cities and subpopulations. This information should be taken into account when planning public health interventions.

FUNDING

European Research Council, National Health and Medical Research Council, and Australian Research Council.

Mortality due to heatstroke and exposure to cold: Evidence from India

The effects of exposure to extreme heat and cold temperatures on human health have mostly been studied in high-income countries. We examined this association by exploring the effect of extreme temperatures on mortality due to heatstroke and exposure to cold in India and by states. We used temperature data from the Indian Meteorological Department (IMD) and mortality data from the National Crime Records Bureau (NCRB) to examine trends in overall, gender, and age-specific mortality. We used structural breaks analysis to observe changes in India's mortality trends during 2001-2019. We examined the time trends in the relationship between extreme temperature and mortality for 24 Indian states from 2001 to 2014. We used panel regression and spline regression models. Between 2001 and 2019, India reported 19,693 and 15,197 deaths due to heatstroke and cold exposure, respectively. Top three states with the greatest number of deaths due to heatstroke were Andhra Pradesh, Uttar Pradesh, and Punjab; for cold exposure it was Uttar Pradesh, Punjab, and Bihar. Working-age men were significantly more susceptible to heatstroke. Spline regression results indicated that mortality varied across different temperature bins for both extreme summer and winter temperatures. Our findings demonstrate an urgent need to strengthen welfare and social support systems and invest in built environment and livelihood interventions to counter the avoidable mortality from extreme temperature events.

Whole genome transcriptomic profiling reveals distinct sex-specific responses to heat stroke

Heat-related mortality remains health challenges exacerbated by climate change, with sex-based differences in outcomes, yet underlying mechanisms remain poorly understood. This study examined transcriptomic responses to heat exposure in peripheral blood mononuclear cells from 19 patients with heat stroke (HS; 8 males, mean age 64.8 ± 6.6 yr; 11 females, mean age 49.7 ± 11 yr) and 19 controls (11 males, mean age 48.9 ± 9.6 yr; 8 females, mean age 44.9 ± 11.8 yr). At admission, gene expression revealed upregulation of heat shock protein genes, and pathway analysis demonstrated activation of heat shock and unfolded protein responses across both sexes consistent with proteotoxic stress. However, distinct metabolic, oxidative stress, cell cycle control, and immune responses were observed within each sex. Females displayed inhibition of protein synthesis, oxidative phosphorylation, and metabolic pathways, including glucose metabolism, indicative of a hypometabolic state. Males maintained metabolic activity precooling and enhanced adenosine triphosphate production postcooling. Females activated nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress responses and inhibited DNA replication and mitosis, potentially mitigating genomic instability, whereas these pathways showed limited regulation in males. Females promoted innate immunity via interleukin (IL)-6, inflammasome, and triggering receptor expressed on myeloid cells 1 (TREM1) signaling, whereas males showed suppression of both innate and adaptive immunity, including IL-12, Th1, and T-cell receptor pathways. Upstream analysis identified over 100 transcription factors in both sexes. Males primarily relied on transcriptional mechanisms, whereas females also exhibited translational regulation via La ribonucleoprotein 1 (LARP1), fragile X messenger ribonucleoprotein 1 (FMR1), insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), and eukaryotic translation initiation factor 6 (EIF6). These findings suggest distinct, sex-specific molecular adaptations to heat stroke, underscoring the need for targeted therapeutic strategies to mitigate heat-induced morbidity and mortality.NEW & NOTEWORTHY Heat-related mortality continues to rise with climate change. Our transcriptomic analysis reveals distinct sex-specific metabolic strategies to heat stroke: females enter a hypometabolic state, an evolutionary adaptation that conserves energy, whereas males sustain metabolic activity. Transcription factors and a subset of translation regulators in females modulate proteostasis and bioenergetics, driving these sex-specific pathways. These novel findings highlight the critical need to consider sex-specific differences in heat-related illnesses and inform carefully targeted interventions to improve patient outcomes.

Municipality assessment of temperature-related mortality risks in Norway

BACKGROUND & AIM

Understanding local vulnerability to heat and cold is crucial for public health planning, yet few studies have provided a nationwide analysis of temperature-related mortality across diverse communities. This study analyses the association between ambient air temperature and non-accidental mortality across mainland Norway, using a constrained hierarchical clustering algorithm to group municipalities with similar geographic, environmental, socioeconomic, and demographic patterns.

METHODS

This study analysed the association between ambient air temperature and non-accidental mortality across 356 Norwegian municipalities, using daily data from 1996 to 2018. We applied a case time series design with distributed lag non-linear models. A downscaling procedure assessed the effect of 21 vulnerability factors on temperature-related mortality risks, using Principal Components Analysis to explore heterogeneity across clusters.

FINDINGS

Cold temperatures contributed to an estimated 3879 deaths per year (95% CI 3718-4130), while heat was associated with 44 deaths annually (95%CI: 29-58). The highest heat-related mortality risk occurred in the South-East, and the highest cold-related risk in the Central-East. Greater heat-related mortality correlated with medium-to sparsely-populated areas, while higher education levels were linked to reduced vulnerability to both heat and cold.

INTERPRETATION

By providing the first comprehensive assessment of temperature-related excess mortality and associated risk factors in Norway, our findings underscore the need for targeted, equitable health policies that integrate environmental and socioeconomic factors. These insights are essential to guide climate adaptation strategies, prioritising vulnerable rural communities and socioeconomically disadvantaged groups to mitigate future climate-related health impacts.

Cardiovascular admission risk attributable to hot apparent temperature: a study in a rural area of northwest China

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, posing a significant threat to public health. Research on the relationship between CVD and temperature has primarily focused on developed urban settings, with limited studies conducted in rural regions with lower levels of development. Additionally, compared to relative risks, attributable risks can provide more information when assessing the risk of CVD hospitalizations associated with exposure to apparent temperature (AT). Apparent temperature is a composite temperature index that takes into account both meteorological factors and temperature, providing an objective reflection of human thermal sensation. Therefore, this study investigates the impact of AT on CVD hospitalization and quantifies the burden of CVD admission in the rural areas of China. We employed the distributed lag non-linear model (DLNM) to estimate the relationship between AT and the relative risk (RR) of CVD hospitalization. Finally, we used attributable risk methods to quantify this relationship further.

Excess mortality related to high air temperature: Comparison of the periods including 1994 and 2018, the worst heat waves in the history of South Korea

Climate change has caused extreme weather events, including frequent summer heat waves. We examined how the effects of high air temperatures on mortality have changed between the two study periods (1991-1995 and 2015-2019), including 1994 and 2018, the worst heat wave years in the meteorological history of South Korea. Temperature data from the Korea Meteorological Administration and mortality data from Statistics Korea were used in this study. We used distributed lag nonlinear models to estimate the cumulative relative risks (CRRs) to determine the association between daily maximum temperature in summer (June to September) and mortality. CRRs were estimated for each province and pooled using a random-effects meta-analysis for all provinces. Maximum temperature and annual average days in heat wave were 37.7°C and 11.8 in 1991-1995 and 38.3°C and 18.8 in 2015-2019. The slope of the CRR for mortality increases with increasing temperature and has been steeper in the past than in recent years and steeper in those over 65 than in those under 65. Excess mortality has recently declined compared with that in the past. The impact of high summer temperatures on mortality changed between the two periods, suggesting improved population resilience.

Analyzing effect modifiers of the temperature-mortality relationship in the Paris region to identify social and environmental levers for more effective adaptation to heat

Adaptation to heat is a major challenge for the Paris region (France). Based on fine-scale data for the 1,287 municipalities of the region over 2000-2017, we analyzed (time-serie design) the temperature-mortality relationship by territories (urban, suburban, rural), age (15-64 and ≥ 65) and sex, and explored how it was modified by vegetation and socio-economic indicators. Heat was associated with an increased mortality risk for all territories, age groups, sex, and mortality causes. Women aged 65 and over residing in the most deprived municipalities had a relative risk (RR) of deaths at 29.4 °C (compared to 16.6 °C) of 4.2 [3.8:4.5], while the RR was 3.4 [3.2:3.7] for women living in less deprived municipalities. Actions to reduce such sex and social inequities should be central in heat adaptation policy.

Socio-environmental modifiers of heat-related mortality in eight Swiss cities: A case time series analysis

In the light of growing urbanization and projected temperature increases due to climate change, heat-related mortality in urban areas is a pressing public health concern. Heat exposure and vulnerability to heat may vary within cities depending on structural features and socioeconomic factors. This study examined the effect modification of the temperature-mortality association of three socio-environmental factors in eight Swiss cities and population subgroups (<75 and ≥ 75 years, males, females): urban heat islands (UHI) based on within-city temperature contrasts, residential greenness measured as normalized difference vegetation index (NDVI) and neighborhood socioeconomic position (SEP). We used individual death records from the Swiss National Cohort occurring during the warm season (May to September) in the years 2003-2016. We performed a case time series analysis using conditional quasi-Poisson and distributed lag non-linear models with a lag of 0-3 days. As exposure variables, we used daily maximum temperatures (Tmax) and a binary indicator for warm nights (Tmin ≥20 °C). In total, 53,593 deaths occurred during the study period. Overall across the eight cities, the mortality risk increased by 31% (1.31 relative risk (95% confidence interval: 1.20-1.42)) between 22.5 °C (the minimum mortality temperature) and 35 °C (the 99th percentile) for warm-season Tmax. Stratified analysis suggested that the heat-related risk at 35 °C is 26% (95%CI: -4%, 67%) higher in UHI compared to non-UHI areas. Indications of smaller risk differences were observed between the low vs. high greenness strata (Relative risk difference = 13% (95%CI: -11%; 44%)). Living in low SEP neighborhoods was associated with an increased heat related risk in the non-elderly population (<75 years). Our results indicate that UHI are associated with increased heat-related mortality risk within Swiss cities, and that features beyond greenness are responsible for such spatial risk differences.