Lifetime History of Indoor Tanning in Young People
Lifetime History of Indoor Tanning in Young People
Subjects for this analysis were controls from a case-control study of early-onset BCC, described in detail elsewhere. This analysis was limited to controls, as these individuals would be more generalizable to the general population than our BCC cases. Briefly, the Yale Study of Skin Health in Young People identified BCC cases and controls with minor benign skin conditions diagnosed between July 1, 2006 and September 30, 2010 through the Yale Dermatopathology database. To be eligible, participants had to: be less than 40 years of age at the time of skin biopsy, reside in Connecticut, speak English, and either the participant (or appropriate guardian for those under age 18) had to be capable of completing all study components. Participants completed a structured in-person interview and several self-administered questionnaires. The study was approved by Yale University's Institutional Review Board and study participants (or guardians) provided appropriate written informed consent.
Potential controls were individuals diagnosed with minor benign skin conditions in the Yale Dermatopathology database during the study period. To determine a list of eligible control conditions for sampling, two dermatologists reviewed a list of all skin conditions diagnosed during a one-year period in persons under age 40 in the Yale Dermatopathology database prior to recruitment. A variety of diagnoses were determined ineligible for sampling, including skin cancers/precancers (e.g., melanoma, squamous cell carcinoma, T-cell lymphomas, actinic keratoses), potentially UV-related benign conditions (e.g., solar lentigo, atypical nevus), erythematous conditions associated with photosensitivity or aggravated by UV exposure (e.g. lupus erythematous, erythema multiforme, rosacea), dermal conditions treated with UV therapy (e.g., psoriasis), and pigment disorders (e.g., vitiligo). Randomly sampled controls were frequency matched to BCC cases on age at biopsy (5 year age groups), gender, and biopsy site (head/neck, trunk, extremity).
A total of 458 controls participated in the study, with a response rate of 60.7% among those able to be directly contacted. Any individual who self-reported a history of BCC during the interview was excluded from the control population. The 458 enrolled controls had a variety of skin conditions; cyst (16.4%), seborrheic keratosis (16.2%) and wart (11.4%) were the three most common and all other diagnoses accounted for < 10% of controls.
During the structured interview, participants were asked about their lifetime use of indoor tanning beds/booths, including regular tanning beds/booths, high speed/high intensity tanning beds/booths, and high pressure tanning beds/booths. Participants were provided color photos of the different types of tanning beds/booths to aid in reporting. We also queried age at which participants first tanned indoors, and number of burns from indoor tanning. Across four specified age periods (ages 11–15, 16–20, 21–30 and 31 or older) frequency of use was also queried. In addition to a dichotomous ever versus never indoor tanning variable, a frequency measure of indoor tanning was calculated: total number of sessions over the four age periods. We also categorized the female ever indoor tanners who were 31 years of age or older into two groups: persistent and non-persistent tanners. Persistent indoor tanners were defined as females who tanned indoors at least once in the last three age periods (excluding the 11–15 age period) or in all four specified age periods.
In addition to sociodemographic information, several other characteristics were ascertained during the interview including: outdoor sunbathing sessions during three time periods (8–15 years old, 16–25 years old, and 26 plus years old), height, weight (age 18 and current), alcohol consumption (red and white wine, hard liquor/mixed drinks, and beer over two age periods; total number of drinks under age 25 and drinks per year ≥ age 25) and tobacco use. Participants were also asked to report their skin color (very fair, fair, light olive, dark olive, brown, very dark brown/black), eye color (grey, blue, green, hazel, brown), skin reaction to strong sunlight for the first time in summer for one hour without sunscreen (severe sun burning with blistering, painful sun burning for a few days followed by peeling, mild burning followed by some degree of tanning, turning brown without any sunburn), and skin reaction upon repeated and prolonged exposure to sunlight (very brown and deeply tanned, moderately tanned, mildly tanned due to a tendency to peel, only freckled with no suntan at all).
This analysis is limited to the 401 (87.5%) self-identified white controls from the total pool of 458 controls. Three individuals in our analytic sample were under age 18 at the time of interview. To evaluate differences between ever indoor tanners and never indoor tanners stratified by gender, we employed the Wilcoxon Rank Sum test and chi-square test. Among the indoor tanners, we used the Wilcoxon Rank Sum test to compare distributions and the z-test to compare proportions between males and females. All variables were first entered into an unadjusted univariate logistic regression model to predict ever versus never indoor tanning. We then constructed a multivariate model using a stepwise procedure; this step was restricted to females given the limited sample size for males. Univariate and multivariate logistic regression models were also built to evaluate characteristics associated with persistent indoor tanning versus non-persistent tanning among female indoor tanners age 31 and older.
For all logistic regression analyses, reported P values correspond to the likelihood ratio test. For the univariate logistic regression analyses, the likelihood ratio test compares a model with the variable of interest to the null model. In the multivariate logistic regression setting, the likelihood ratio test compares the full model to the full model minus the variable of interest. Variables with a P value less than 0.1 were retained in the multivariate models. All analyses were conducted using R and reported P values are two-sided.
Methods
Yale Study of Skin Health in Young People
Subjects for this analysis were controls from a case-control study of early-onset BCC, described in detail elsewhere. This analysis was limited to controls, as these individuals would be more generalizable to the general population than our BCC cases. Briefly, the Yale Study of Skin Health in Young People identified BCC cases and controls with minor benign skin conditions diagnosed between July 1, 2006 and September 30, 2010 through the Yale Dermatopathology database. To be eligible, participants had to: be less than 40 years of age at the time of skin biopsy, reside in Connecticut, speak English, and either the participant (or appropriate guardian for those under age 18) had to be capable of completing all study components. Participants completed a structured in-person interview and several self-administered questionnaires. The study was approved by Yale University's Institutional Review Board and study participants (or guardians) provided appropriate written informed consent.
Potential controls were individuals diagnosed with minor benign skin conditions in the Yale Dermatopathology database during the study period. To determine a list of eligible control conditions for sampling, two dermatologists reviewed a list of all skin conditions diagnosed during a one-year period in persons under age 40 in the Yale Dermatopathology database prior to recruitment. A variety of diagnoses were determined ineligible for sampling, including skin cancers/precancers (e.g., melanoma, squamous cell carcinoma, T-cell lymphomas, actinic keratoses), potentially UV-related benign conditions (e.g., solar lentigo, atypical nevus), erythematous conditions associated with photosensitivity or aggravated by UV exposure (e.g. lupus erythematous, erythema multiforme, rosacea), dermal conditions treated with UV therapy (e.g., psoriasis), and pigment disorders (e.g., vitiligo). Randomly sampled controls were frequency matched to BCC cases on age at biopsy (5 year age groups), gender, and biopsy site (head/neck, trunk, extremity).
A total of 458 controls participated in the study, with a response rate of 60.7% among those able to be directly contacted. Any individual who self-reported a history of BCC during the interview was excluded from the control population. The 458 enrolled controls had a variety of skin conditions; cyst (16.4%), seborrheic keratosis (16.2%) and wart (11.4%) were the three most common and all other diagnoses accounted for < 10% of controls.
Measures
During the structured interview, participants were asked about their lifetime use of indoor tanning beds/booths, including regular tanning beds/booths, high speed/high intensity tanning beds/booths, and high pressure tanning beds/booths. Participants were provided color photos of the different types of tanning beds/booths to aid in reporting. We also queried age at which participants first tanned indoors, and number of burns from indoor tanning. Across four specified age periods (ages 11–15, 16–20, 21–30 and 31 or older) frequency of use was also queried. In addition to a dichotomous ever versus never indoor tanning variable, a frequency measure of indoor tanning was calculated: total number of sessions over the four age periods. We also categorized the female ever indoor tanners who were 31 years of age or older into two groups: persistent and non-persistent tanners. Persistent indoor tanners were defined as females who tanned indoors at least once in the last three age periods (excluding the 11–15 age period) or in all four specified age periods.
In addition to sociodemographic information, several other characteristics were ascertained during the interview including: outdoor sunbathing sessions during three time periods (8–15 years old, 16–25 years old, and 26 plus years old), height, weight (age 18 and current), alcohol consumption (red and white wine, hard liquor/mixed drinks, and beer over two age periods; total number of drinks under age 25 and drinks per year ≥ age 25) and tobacco use. Participants were also asked to report their skin color (very fair, fair, light olive, dark olive, brown, very dark brown/black), eye color (grey, blue, green, hazel, brown), skin reaction to strong sunlight for the first time in summer for one hour without sunscreen (severe sun burning with blistering, painful sun burning for a few days followed by peeling, mild burning followed by some degree of tanning, turning brown without any sunburn), and skin reaction upon repeated and prolonged exposure to sunlight (very brown and deeply tanned, moderately tanned, mildly tanned due to a tendency to peel, only freckled with no suntan at all).
Statistical Analysis
This analysis is limited to the 401 (87.5%) self-identified white controls from the total pool of 458 controls. Three individuals in our analytic sample were under age 18 at the time of interview. To evaluate differences between ever indoor tanners and never indoor tanners stratified by gender, we employed the Wilcoxon Rank Sum test and chi-square test. Among the indoor tanners, we used the Wilcoxon Rank Sum test to compare distributions and the z-test to compare proportions between males and females. All variables were first entered into an unadjusted univariate logistic regression model to predict ever versus never indoor tanning. We then constructed a multivariate model using a stepwise procedure; this step was restricted to females given the limited sample size for males. Univariate and multivariate logistic regression models were also built to evaluate characteristics associated with persistent indoor tanning versus non-persistent tanning among female indoor tanners age 31 and older.
For all logistic regression analyses, reported P values correspond to the likelihood ratio test. For the univariate logistic regression analyses, the likelihood ratio test compares a model with the variable of interest to the null model. In the multivariate logistic regression setting, the likelihood ratio test compares the full model to the full model minus the variable of interest. Variables with a P value less than 0.1 were retained in the multivariate models. All analyses were conducted using R and reported P values are two-sided.
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