Urine collection
Participants collected their urine for 24 h starting on Day 9. Urine was assessed for volume, urine specific gravity (Goldberg Brix Refractometer, Reichert Technologies, Depew, NY), electrolyte concentrations (EasyElectrolyte Analyzer, Medica, Bedford, MA), and osmolality (Advanced 3D3 Osmometer, Advanced Instruments, ON, Canada). Urine flow rate was calculated and used to determine 24‐h sodium excretion. Urine collections were considered valid if collected within 20–28 h, there were not ≥2 missed collections, and volume was ≥500 mL. The first morning void was collected separately on Day 10 to assess melatonin compliance by measuring urinary 6‐sulfatoxymelatonin (ELISA kit, Alpco, Salem, NH). A 4 Parameter Logistics curve fit was used to obtain the calibrator curve with SoftMax Pro Software (Molecular Devices). Values at or above the maximum detectable level of the assay were assigned that value for statistical analysis purposes.