Symptoms of heat stress predict changes in serum creatinine among rural patients with chronic kidney disease during heatwave conditions in Northern India.

BACKGROUND: Heat waves are being increasingly experienced in many parts of the world, including in subtropical dry zones in northern India. Patients with pre-existing chronic kidney disease are more likely to develop acute kidney injury, but the extent of the problem and its predictors are currently unknown. The objective of the present prospective, observational study was to evaluate the association between self-reported heat stress symptoms and changes in kidney function during heat wave conditions, among patients conforming to chronic kidney disease of unknown etiology (CKDu) clinical phenotype. METHODS: The study participants were recruited in the months of April-May in 2023 and 2024, from an ongoing hospital-based registry for patients with CKD conforming to CKDu clinical phenotype from central and eastern districts of Uttar Pradesh. In addition to clinical, information, symptoms of self-reported heat stress [modified from health hazard evaluation of heat stress (HETA questionnaire)] were noted. The questionnaire has sixteen questions, each scored ordinally from 0 to 2 for frequency of the symptom, and therefore, a maximum score of 32, constituting the heat stress index. Blood was drawn for serum creatinine at study inclusion and at one month (in the same lab providing isotope dilution mass spectrometry (IDMS)-traceable values), among study participants and all were advised for maintaining hydration, avoiding continuous outdoor heat exposure > 2 h and continued on usual care. RESULTS: Of a total of 266 screened patients with CKD from the hospital-based registry, 138 were included in the final analysis, of whom 58 reported agriculture as their occupation (42%), 53% were males, majority belonged to CKD Stage III (38%) and 64% had mild hypertension. The median heat stress index among the study participants was 6 (IQR 3-9) and 58.7% had any reduction of serum creatinine, with 24.6% having > 10% reduction on repeat serum creatinine values drawn at a median of 38 days (IQR 26-45). Baseline estimated glomerular filtration rate and heat stress index were significant predictors for reduction of serum creatinine in a multivariate logistic regression model. [odds ratio 1.028 (95% confidence interval = 1.003-1.053), p value = 0.028 and odds ratio 1.196 (95% confidence interval = 1.076-1.329), p value = 0.001, respectively]. CONCLUSION: Among rural patients from northern India with chronic kidney disease pertaining to CKDu phenotype, during heat wave conditions, heat stress index predicted any reduction of serum creatinine after one month. TRIAL REGISTRATION DETAILS: The study was prospectively registered with Clinical Trials Registry of India (CTRI) as CTRI/2023/01/049117 dated 19-01-2023.