| Abstract: | This study examined whether 15‐hr and 24‐hr urinary catecholamine measures show comparable associations with other physiological measures that are expected to correlate with sympathetic nervous system activity. Participants (193 healthy adults) provided 24‐hr urine samples that were collected in a controlled environment (hotel), and divided into 9‐hr daytime and 15‐hr overnight collections. On the same day, resting blood pressure (BP) was measured, and 8 samples of salivary Cortisol were collected. Catecholamine (15‐hr and 24‐hr) measures were correlated substantially in the entire sample, and when examined separately by sex and by race. Both 15‐hr and 24‐hr epinephrine (E) correlated significantly with systolic BP and Cortisol; 15‐hr and 24‐hr norepinephrine (NE) correlated significantly with Cortisol. Correlation coefficients for 15‐hr measures were similar, but not equivalent to those for 24‐hr measures. Urinary catecholamines obtained via 15‐hr overnight collection approximated but were not equivalent to catecholamines obtained via 24‐hr collection. Overnight collection was associated with reduced power to detect significant associations of catecholamines with criterion variables, such that use of 15‐hr rather than 24‐hr sampling required a relative increase in sample size of 1.32 times for E and 1.18 times for NE to detect similar effects. Researchers should weigh the costs of additional subjects to the benefit of decreased burden when choosing between the two sampling methods. |
