Passive Heat Therapy Compared To Aerobic Exercise In Reducing Albuminuria In Adults With Untreated Hypertension

Albuminuria is an independent risk factor for chronic kidney disease, cardiovascular disease, and all-cause mortality and is prevalent in 40% of adults with untreated hypertension, while urinary creatinine excretion above and below normal levels is associated with impaired renal function. Physical activity is recommended for improving cardiovascular and chronic kidney disease risk profiles but has poor adherence. Recent evidence suggests heat therapy may be a viable alternative to exercise for reducing urine albumin excretion. PURPOSE: To test the hypothesis that chronic hot water immersion (HWI) reduces urine albumin excretion in adults with untreated hypertension to a greater extent than aerobic exercise training (EX). METHODS: Participants (n = 23, 6F; 47 ± 7 years) were randomized and completed either 30 sessions of HWI (n = 10, 2F) or EX (n = 13, 4F) over ~10 weeks. For HWI, participants were immersed to mid sternum in 40 °C water for 45 min with a 5-min recovery. EX consisted of upright cycling at 60% of heart rate reserve (HRR) for 40 min, with a 5-min warm-up and cool-down at 30% HRR. Blood pressure was measured and a 24-hour urine collection protocol was completed before (PRE) and after completion of all 30 sessions (POST). Urine albumin excretion was quantified via ELISA, and urine creatinine excretion was quantified via colorimetric assay. Data were analyzed PRE vs. POST for EX and HWI using a two-way repeated measures ANOVA and are presented as mean ± SD. RESULTS: There was no effect of time (p = 0.67), group (p = 0.61), or group x time interaction (p = 0.16) for 24 h urine albumin excretion PRE vs. POST for EX (10.6 ± 6.6 vs. 18.4 ± 25.6 mg/24 h) or HWI (25.6 ± 49.9 vs. 10.3 ± 7.3 mg/24 h). For 24 h urine creatinine excretion, there was a significant interaction effect (p = 0.034). EX was reduced at POST (1612 ± 485 vs 1443 ± 391 mg/24 h, p = 0.049), while HWI was not different (1518 ± 493 vs 1620 ± 465 mg/24 h; p = 0.25). CONCLUSION: Among adults with untreated hypertension, aerobic exercise training has a greater impact on reducing 24 h urinary creatinine excretion than hot water immersion, with both PRE and POST within normal ranges. Neither intervention impacted urinary albumin excretion, suggesting these interventions may not reduce urine albumin excretion in adults with untreated hypertension. NIH R01HL144128 NIH F32HL164021