Psychometrically sound measurement of skin color and damage is important for surveillance in skin cancer prevention and intervention efforts. While the current study did not include an assessment of skin cancer, the study is unique in its use of observer ratings of skin color, UV photographs to assess cumulative skin damage, and its comparison of four different skin color and damage measurement strategies. Reliable ratings of UV photo damage were obtained. Moderate to high correlations emerged between self-report of skin color and the gold standard, skin reflectance spectrophotometery, indicating that these measures have convergent validity. Observer rating correlated with spectrophotometry rating of current but not natural skin color, suggesting that observer rating of current skin color converges with the gold standard skin reflectance spectrophotometry, although observer rating of natural skin color does not. Overall, lighter-skinned individuals reported more cumulative skin damage, which was supported by UV photography. Although women's current skin color was lighter and their UV photos showed similar damage to men's, women reported their skin to be significantly more damaged than men did.
Previous studies have used viewing UV photos as an intervention to promote skin cancer prevention behaviors (Gibbons et al., 2005
; Mahler et al., 2007
; Mahler et al., 2003
; Mahler et al., 2005
; Pagoto et al., 2003
), but none have assessed their utility as an outcome measure of intervention effect. As expected, the UV photos were able to be rated reliably in the current study; however, the ratings were only minimally correlated with self-report ratings of cumulative skin damage. The small correlation between UV photos and self-report of damage suggests that these measures have low convergent validity; however, the small correlation may represent self-report bias or misjudgment of damage. Because the photos were only compared with self-report of cumulative damage, this does not allow us to draw conclusions about the validity of the UV photos. In future studies, the validity of the photo ratings could be assessed by monitoring exposure and protective behaviors longitudinally or by creating a more comprehensive self-report scale measuring cumulative UV damage including items inquiring about UV exposure and protection behaviors over time. Additionally, the use of UV photos with darker-skinned individuals needs to be evaluated further. Finally, digital UV photography is now available, which allows even greater accuracy and versatility.
The use of a simple 1-7 Likert scale for self-report of natural skin color was found to correlate better with the other measures of interest than the more sophisticated and commonly-used Fitzpatrick (Fitzpatrick, 1988
) scale measuring skin sensitivity. Clinically, our group has noted that individuals typically underestimate their skin sensitivity. Self-report of natural skin color was moderately to highly correlated with spectrophotometry readings for each body area that was measured, again supporting convergent validity. The strength of this correlation is impressive given that self-report was compared to a “gold standard.” Interestingly, the correlation was similar regardless of which body area was measured. Spectrophotometry measurements of the upper inner arm were highly correlated with both the facial cheek and the lower outer arm. The similarity of the spectrophotometry ratings indicates that measuring the upper inner arm may not accurately reflect a body area that does not receive UV exposure as suggested previously (Mahler et al., 2007
). We could have analyzed our data using lower arm minus upper arm spectrophotometry readings to indicate tanness. However, prior research has found that spectrophotometry measurements of the upper inner arm change over time with UV exposure (Mahler, personal communication, 2006). Likewise, we found very few people whose lower arm was significantly darker than their upper arm. Assessment of lower exposure body areas, however, may be more successful in high exposure settings (i.e., warm climates) or times of the year (i.e., summer).
Observer rating of tanness was moderately to highly correlated with spectrophotometry scores from the facial cheek and lower arm, but observer rating of untanned skin color was not correlated with spectrophotometry measurement of the upper arm. Thus, spectrophotometry readings converge with observer rating of tanness but not observer rating of untanned skin color. In other words, the rater was relatively successful at rating what she actually saw in person, but was also given the difficult task of rating what she would have seen if participants had no tan. Additionally, the rater generally only saw the face, arms, and hands of the participants in an individual session with no opportunity to compare their skin color to others, thus the failure to find a significant association is not surprising. A more accurate way to gather observer ratings would be to have the observer rate current skin color, perceived race/ethnicity, examine areas of the body that might receive more or less UV exposure, or to compare individuals to others or to standard images. Ideally, more than one observer or an expert observer such as a dermatologist would be utilized, but this was not feasible in the current study. Likewise, we took only black and white photos, but obtaining color photos might have allowed for more comprehensive observer ratings.
Lighter-skinned individuals, as determined by spectrophotometry, self-rating, or race/ethnicity, reported more cumulative skin damage than darker-skinned individuals. This is not surprising given that light-skinned individuals are at higher risk of skin damage such as sunburns and skin cancer, particularly when not well protected (Bajdik et al., 1998
; Böni et al., 2002
; Davis et al., 2002
; Hall et al., 2003
). These results support one form of discriminant validity of spectrophotometry and self-rating. Although the differences in self-rated skin damage between dark and light-skinned individuals were statistically significant, they were not large in absolute terms. Given the low report of damage, it is possible that some participants under-reported their amount of skin damage because even the light-skinned individuals did not rate their damage as above four out of seven on average, and participants were selected for having at least one skin cancer risk factor (Fitzpatrick, 1988
Interestingly, although women's current skin color was lighter and their UV photos showed similar damage to men's, women reported their skin to be significantly more damaged than men did. Which sex was a more accurate judge of skin damage is unclear without further assessment of skin color and damage. For example, darker skinned men may have reported more damage based on recent tanning behavior. However, lighter skinned women may have reported more damage based on prior burning experiences. Prior studies have found that women both tan more and protect their skin more (e.g., use sunscreen) than men (Steffen et al., 2007
; Thieden et al., 2005
; Weinstock et al., 2000
). This gender difference is likely due to greater appearance concern and cultural pressure to be attractive for females (Boldeman et al., 2003
; Boldeman et al., 1997
; Demko et al., 2003
; O'Riordan et al., 2006
). Although American men are at higher risk for melanoma than American women (Ries et al., 2006
), men in the current sample self-reported significantly less skin damage than did women. Therefore, different skin cancer prevention interventions may be appropriate for men and women, or at least subgroups of individuals with high UV exposure and low protective behaviors or other skin cancer risk factors such as a family history of skin cancer. However, more research is needed in this area because the current study sample included only 18 men and 82 women.
Limitations of the study are that it utilized a cross-sectional convenience sample, and only a small number of items were rated by the participants and the observer. A convenience sample of individuals responding to advertisements may differ in a variety of ways from individuals selected randomly. Study findings suggest that self-report continues to be a valuable measurement strategy when measuring skin reflectance is not feasible or appropriate and that UV photos may also be useful but need to be tested further. Observer rating of skin color were satisfactory but may be improved through the use of additional measures or with more comprehensive protocols or training. Future research should continue to test these measurement strategies with larger and more diverse populations and compare them with other types of measures over time such as behavioral observation or objective measurement of UV exposure and protective behaviors such as dosimeters measuring real-time UV exposure and skin swabbing for evidence of adequate sunscreen application (for a review, see (Glanz and Mayer, 2005
). Longitudinal studies could also evaluate the predictive validity of some of these measures. Skin cancer rates and exposure behaviors such as indoor tanning are rising, while protective behaviors such as sunscreen use remain steady (Feldman et al., 2004
; Lamberg, 2002
; NCI, 2007
; Robinson et al., 1997
). Adequate measurement of skin color and damage is important for surveillance in prevention and intervention efforts. To this end, we must determine which measures are most reliable, valid, convenient, and cost-effective for specific situations.