Heat-related acute kidney injury risk in England: a nationwide case-crossover analysis of 947 342 AKI alerts.

BACKGROUND

Acute kidney injury (AKI) incidence is rising and while heat-AKI associations are established, the demographic and clinical groups most vulnerable remain unclear. Identifying these groups is essential for kidney-specific heatwave guidance.

METHODS

A total of 947 342 AKI alerts in England from April to September 2017-21, from UK Renal Registry data, were linked to HadUK-Grid dataset and hospital admission data. We utilized a time-stratified, bidirectional case-crossover design with distributed lag models estimated odds ratios (ORs) for AKI associated with temperatures above 25°C, stratified by demographic characteristics and admission diagnosis.

RESULTS

Heat exposure was associated with AKI [OR 1.038; 95% confidence interval (CI) 1.036-1.040 per 1°C rise above 25°C] with highest odds for stage 3 AKI (OR 1.047; 95% CI 1.039-1.055). Associations were more marked in males (OR 1.041; 95% CI 1.037-1.044) than females (OR 1.035; 95% CI 1.032-1.039); odds doubled in those aged ≥85 years (OR 1.054; 95% CI 1.049-1.060) compared with the 45-64 years age group (OR 1.027; 95% CI 1.021-1.032). Ethnic risks varied between Chinese (OR 1.054, 95% CI: 1.012-1.098), White (OR 1.041; 95% CI 1.038-1.044), Indian (OR 1.033; 95% CI 1.019-1.047), Pakistani/Bangladeshi (OR 1.027; 95% CI 1.011-1.044), Caribbean (OR 1.024; 95% CI 1.005-1.042) and African (OR 1.001; 95% CI 0.982-1.021), with differences partly explained by younger age distribution in ethnic minority groups. Heat-related AKI was more marked for admissions of patients with delirium (OR 1.061; 95% CI 1.029-1.094) and with respiratory diseases (OR 1.044; 95% CI 1.037-1.052).

CONCLUSIONS

There was effect modification by age for heat-related AKI risk, with especially high risks amongst older individuals; those admitted with delirium or respiratory illness and some ethnic groups. These findings support the development of targeted kidney-specific hot weather guidance to protect the vulnerable populations identified.