Mayrovitz Harvey N
Department of Medical Education, Dr. Kiran C. Patel College of Allopathic Medicine, Nova Southeastern University, Fort Lauderdale, Florida, USA.
Skin Pharmacol Physiol. 2024;37(4-6):80-91. doi: 10.1159/000541547. Epub 2024 Sep 19.
Three interrelated skin water assessments include stratum corneum hydration (SCH) via electrical measurements, skin water using tissue dielectric constant (TDC) measurements, and transepidermal water loss (TEWL). These are differentially used for skin physiology research, clinical assessments of dermatological conditions and to assess skin water in diabetes and lymphedema. Often volar forearm skin is used for assessments done at various times of day (TOD). The present goal was to assess the extent of intraday variability in SCH, TDC, and TEWL.
Twelve medical students self-measured SCH, TDC, and TEWL on their forearm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All participants were well trained and pre-certified in all procedures. Tests for parameter differences among TOD were via the nonparametric Friedman test.
No significant differences in SCH or TEWL were found among TOD over the 16-h interval for either day or combined. Contrastingly, TDC decreased slightly but significantly from morning through evening. There was no evidence of a diurnal pattern. Interestingly, a significant nonlinear relationship between TEWL and SCH was detected.
Findings indicate only minor intraday variations with TOD trend except for TDC which decreases slightly from morning through evening. The clinical relevance relates to the confidence now gained associated with the parameter estimates when measured at different TOD during normal clinic hours or beyond. This should help in estimating the potential importance of small differences if measured at a different TOD. From a physiological viewpoint, the findings uncover and describe an interesting nonlinear relationship between TEWL and SCH which may serve to propel further investigations that might better characterize this process.
三项相互关联的皮肤水分评估包括通过电学测量评估角质层水合作用（SCH）、使用组织介电常数（TDC）测量评估皮肤水分以及经表皮水分流失（TEWL）。这些评估在皮肤生理学研究、皮肤病临床评估以及糖尿病和淋巴水肿患者的皮肤水分评估中有着不同的应用。通常使用掌侧前臂皮肤在一天中的不同时间（TOD）进行评估。本研究的目的是评估SCH、TDC和TEWL在一天内的变化程度。
12名医学生在连续两天的08:00至24:00期间，每隔2小时自行测量一次前臂的SCH、TDC和TEWL。所有参与者均接受了充分的培训，并在所有测量程序方面预先获得认证。通过非参数Friedman检验来检测不同时间点之间参数的差异。
在16小时的时间段内，无论是单日还是合并两天的数据，不同时间点之间的SCH或TEWL均未发现显著差异。相比之下，TDC从早晨到晚上略有但显著下降。没有证据表明存在昼夜模式。有趣的是，检测到TEWL与SCH之间存在显著的非线性关系。
研究结果表明，除了TDC从早晨到晚上略有下降外，其他指标在一天内仅有微小变化，且无明显的时间变化趋势。这一结果的临床意义在于，在正常门诊时间或其他时间进行测量时，现在可以更有信心地获得参数估计值。这有助于评估在不同时间点测量时微小差异的潜在重要性。从生理学角度来看，研究结果揭示并描述了TEWL与SCH之间有趣的非线性关系，这可能有助于推动进一步的研究，从而更好地描述这一过程。
