Gender-Specific Differences of Renal Heat Tolerance in Older Adults during Heat Waves

Abstract

Background: Heat waves are known to cause increased morbidity and mortality in susceptible populations like old and functionally impaired people. The objective of the study was to assess renal tubular stress, a predictor for development of acute kidney injury, during heat waves in Central Europe. As a marker of renal tubular stress tissue inhibitor of metalloproteinases-2 [TIMP-2]·insulin-like growth factor binding protein-7 [IGFBP7], a new FDA-cleared renal tubular stress biomarker, was used. Materials and Methods: 68 residents from facilities of sheltered housing with urine samples collected at heat waves in 2015 and at control visits were included. Urinary [TIMP-2]·[IGFBP7] was compared between the heat waves and the control visits. Multivariate linear models were adjusted for age, frailty index, and functional comorbidity index. Results: The median age was 82.0 years, 82.3% were women. The percentage of elevated levels of urinary [TIMP-2]·[IGFBP7] (>0.3 [ng/mL]2/1,000) in the total study population was higher at the heat waves than at the control visits (25.0% vs. 17.7%). The effect of the heat waves on urinary [TIMP-2]·[IGFBP7] was stronger in men than in women: The percentage of elevated levels was 75.0% in men and 14.3% in women. In the multivariate analysis, the mean urinary [TIMP-2]·[IGFBP7] was 0.48 (95% CI 0.25; 0.70) (ng/mL)2/1,000 higher in men than in women. Except gender, a number of additional variables did not show an association with urinary [TIMP-2]·[IGFBP7] at the heat waves or the control visits. Conclusions: At heat waves, urinary [TIMP-2]·[IGFBP7] was elevated and higher in men than in women. This suggests gender-specific differences in renal heat tolerance in older people.