Reliability and validity of a bioimpedance measurement device in the assessment of UVR damage to the skin.

Ultraviolet radiation (UVR) is the primary cause of skin cancers. However, it is difficult to evaluate the amount of UVR absorbed into the skin retrospectively. Therefore, objective and non-invasive quantitative method would be valuable for epidemiological UVR exposure assessment. Photodamage reduces the amount of bound water in the skin, and thus, measuring the skin's dielectric constant can provide an opportunity for assessing the cumulative UVR exposure. The purpose of the study was to assess the reliability and validity of the bioimpedance device, Moisture Meter-D. The measurements were performed on 100 subjects at three separate measurement times. A questionnaire was used to obtain information on the host factors and on the past UVR exposure. The biological samples, to determine the elastin proportion of the dermis, were collected. Some long-term as well as seasonal variations in the dielectric constants were detected. Also, a weak relationship between the dielectric constant and the UVR exposure indicators and host factors was observed. The MoistureMeter-D appears not to measure structural alterations in the skin caused by photodamage, and thus it is not a valid instrument for the assessment of photodamage, i.e., past UVR exposure.