Intra-day variations in volar forearm skin hydration

Area of Science:

• Dermatology and Skin Physiology
• Biomedical Engineering
• Clinical Measurement Science

Background:

• Skin hydration (SKH) measurements are vital for understanding skin physiology and diagnosing dermatological conditions.
• Localized skin water assessment is important for pathologies like diabetes and lymphedema.
• Volar forearm measurements are commonly used, but intra-day variations require characterization.

Purpose of the Study:

• To characterize intra-day variations in volar forearm skin hydration.
• To provide guidance on the time-of-day dependence of skin hydration measurements.
• To inform clinical practice regarding the reliability of skin hydration estimates.

Main Methods:

• Forty medical students (20 male) self-measured tissue dielectric constant (TDC) on their non-dominant forearm every 2 hours from 0800 to 2400.
• Participants were trained and pre-certified in the TDC measurement procedure.
• Whole-body fat (FAT%) and water (H2O%) were measured; day average TDC (TDC_AVG) was calculated.

Main Results:

• Females exhibited a significant decreasing trend in TDC from morning to night (p=0.004), while males showed no significant trend.
• TDC_AVG was higher in males (32.7 ± 4.1) compared to females (28.5 ± 5.1) (p=0.008).
• TDC values were not significantly impacted by H2O% or FAT%.

Conclusions:

• Skin water assessed by TDC demonstrates intra-day variations with distinct temporal patterns in males and females.
• Clinical relevance lies in understanding the confidence level of skin hydration estimates at different times of day.
• Expected variation is approximately 5% for both sexes during normal clinic hours.