Testing Multi-Theory Model (MTM) in Explaining Sunscreen Use among Florida Residents: An Integrative Approach for Sun Protection

Florida residents have the second highest incidence of skin cancer in the nation. Sunscreen usage was found to be the one of the most effective integrative health approaches for reducing risk of skin cancer. Given the limited information on the likelihood of adopting and continuing sunscreen usage behavior, this cross-sectional study aimed to examine the correlates of initiating and sustaining sunscreen usage behavior among Florida dwellers, using the fourth-generation, multi-theory model (MTM) of behavior change. A web-based survey containing 51 questions was emailed to Florida residents aged 18 years or above, who were randomly selected from the state voter file. Psychometric validity of the survey instrument was established using structural equation modeling, and Cronbach’s alpha values were calculated for assessing the internal consistency. An independent-samples-t-test and hierarchical multiple regression tests were used to analyze the data. The results indicated that participants who engaged in sunscreen usage behavior, participatory dialogue (β = 0.062, p < 0.05), behavioral confidence (β = 0.636, p < 0.001), and changes in the physical environment (β = 0.210, p < 0.001) were statistically significant and accounted for 73.6% of the variance in initiating sunscreen usage behavior. In addition, the constructs of emotional transformation (β = 0.486, p < 0.001) and practice for change (β = 0.211, p < 0.001), as well as changes in the social environment (β = 0.148, p < 0.001) were significant predictors of maintaining sunscreen usage behavior and contributed to 59% of variance in sustenance. These findings offer a valuable insight regarding the applicability of MTM models to guiding public health interventions promoting sunscreen usage and preventing UV radiation risk and related skin cancer.


Introduction
Sunscreen offers an integrative health approach to sun protection, to prevent skin cancers. Skin cancer is among the most common forms of cancers in the United States (U.S.), affecting nearly 10,000 people every day [1]. Over three million cases of non-melanoma skin cancers (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), are diagnosed annually, with one in five Americans projected to develop the cancer during their lifetime [2]. The incidence rates may vary across states and regions, depending upon sociodemographic and environmental factors, and rates of cancer screening [1,3]. study aims to investigate the predictability of adopting and continuing sunscreen usage behavior among a high UV index risk population: Florida residents.

Setting, Study Design, and Sample
This study is a cross-sectional study of the general population of Florida, which is the third largest state in the U.S., with a diverse demography [28]. The data for this study were collected through a web-based survey; launched on 11 June 2021 and closed on 27 June 2021. All participants were required to be 18 years or above, current residents of Florida, and able to read and write in English. No other exclusion criteria were applied.

Sample Recruitment
Invitations to participate in this study were sent through emails, which were randomly selected from the Florida vote file. Initial emails were sent to all potential respondents (~100 k) and a follow-up reminder email was sent after 4 days to the non-respondents. We oversampled (~41 k) to reach underrepresented populations to yield a representative sample comparable to the census distribution according to the latest American Community Survey population estimates.

Study Approval and Data Protection Compliance
The study (protocol #1015079-8) received an exempt status by the Institutional Review Board (IRB), University of North Florida. All participants received a detailed participant information sheet outlining the purpose of the study, exact details related to participation (associated risks and benefits), and how information would be stored and disseminated as one or another form of scholarly product. Participants were also informed about their voluntary participation and that they could withdraw from the study at any time. Detailed contact information of the principal investigator was provided if participants had any questions about the study. Data integrity was ensured in accordance with all data privacy laws and regulations. Principal investigators shared deidentified password protected data files with the analyst of this study. The data were stored in a locked computer and analysis results were shared in an aggregate form with the rest of the research team members.

Quality Control and Authenticity of Responses
Several quality control measures were applied to ensure authenticity of the responses. The "Prevent Ballot Box Stuffing" option was selected in the Qualtrics to limit only one response from each participant to collect unique responses. Invalid or incomplete entries were removed.

Survey Instrument
The initial draft of the survey was sent to seven panelists (including three authors). All were experts in instrumentation in social and behavioral health sciences, five were experts on MTM, two were experts in sun protection research, and three were chosen from the target population. The instrument was validated for face and content validity, along with readability, in two rounds. A total of 16 changes were made during two rounds. Consensus was reached between the experts after two rounds, to finalize the survey instrument. To minimize observer bias, all reviewers were blinded. A 51-item survey MTM based questionnaire was created to examine determinants of sunscreen use among Florida residents. The Flesch reading ease of the entire scale was 66.9 and the Flesch-Kincaid grade level was 5.7 (or less than sixth grade). The survey was composed of 20 questions related to demography, outdoor activities, sunscreen use, and medical history. In addition, 31 items were related to two primary MTM theoretical constructs (initiation and sustenance). The initiation component comprised three constructs which included participatory dialogue, behavioral confidence, and changes in physical environments. "Participatory dialogue" between interventionist and subject evaluates the advantages and disadvantages of initiating an action [28][29][30]. "Behavioral confidence" is like selfefficacy but with subtle differences, it focuses on the self-confidence of the individual in acting. "Changes in physical environment" emphasizes the need for the subject to modify available resources and settings for a behavior to occur. The other component, sustenance (a continuation of behavior) comprises another three constructs: emotional transformation, practice for change, and changes in social environment. "Emotional transformation" involves changes in feelings and attitude and in this process, an individual prepares mentally to sustain the action [28][29][30]. "Practice for change" is a reflective process that continues while person is in action phase. The individual monitors behavioral progress and brings needed changes to sustain the behavior. "Changes in social environment" captures the available support around the individual that is conducive to sustaining the behavior [28][29][30]. A visual representation of MTM constructs is provided in Figure 1.
based questionnaire was created to examine determinants of sunscreen use among Florida residents. The Flesch reading ease of the entire scale was 66.9 and the Flesch-Kincaid grade level was 5.7 (or less than sixth grade). The survey was composed of 20 questions related to demography, outdoor activities, sunscreen use, and medical history. In addition, 31 items were related to two primary MTM theoretical constructs (initiation and sustenance). The initiation component comprised three constructs which included participatory dialogue, behavioral confidence, and changes in physical environments. "Participatory dialogue" between interventionist and subject evaluates the advantages and disadvantages of initiating an action [28][29][30]. "Behavioral confidence" is like self-efficacy but with subtle differences, it focuses on the self-confidence of the individual in acting. "Changes in physical environment" emphasizes the need for the subject to modify available resources and settings for a behavior to occur. The other component, sustenance (a continuation of behavior) comprises another three constructs: emotional transformation, practice for change, and changes in social environment. "Emotional transformation" involves changes in feelings and attitude and in this process, an individual prepares mentally to sustain the action [28][29][30]. "Practice for change" is a reflective process that continues while person is in action phase. The individual monitors behavioral progress and brings needed changes to sustain the behavior. "Changes in social environment" captures the available support around the individual that is conducive to sustaining the behavior [28][29][30]. A visual representation of MTM constructs is provided in Figure 1.

Statistical Analysis
Participants' responses were first preprocessed and then exported to IBM SPSS version 27.0 (IBM Corp. Armonk, NY, USA) for statistical analyses. Incomplete responses and those with invalid data entries were excluded. Mean and standard deviation were used to represent continuous variables. Counts and proportions were used to express categorical variables. Inferential statistics were conducted through independent samples-t-tests to perform group-wise comparisons. Cronbach's alpha values were computed for the entire scale and subscales to assess the internal consistency. Two hierarchical regression models (HRM) were fit to explain the variance in the likelihood of initiation and sustenance of sunscreen use behavior by MTM individual constructs, besides the demographic variables. Structural equation modeling (SEM) was utilized for the construct validation. The

Statistical Analysis
Participants' responses were first preprocessed and then exported to IBM SPSS version 27.0 (IBM Corp. Armonk, NY, USA) for statistical analyses. Incomplete responses and those with invalid data entries were excluded. Mean and standard deviation were used to represent continuous variables. Counts and proportions were used to express categorical variables. Inferential statistics were conducted through independent samples-t-tests to perform group-wise comparisons. Cronbach's alpha values were computed for the entire scale and subscales to assess the internal consistency. Two hierarchical regression models (HRM) were fit to explain the variance in the likelihood of initiation and sustenance of sunscreen use behavior by MTM individual constructs, besides the demographic variables. Structural equation modeling (SEM) was utilized for the construct validation. The Analysis of Moment Structure, AMOS (Chicago, IL, USA) was used for SEM [27]. We used indices such as chi-square (χ 2 ), root mean square error of approximation (RMSEA), comparative fit index (CFI), and Tucker-Lewis (TLI) to assess how well our models fit the data [31][32][33]. Models were considered to have adequate fit if they met the less stringent, but traditionally accepted, values of 0.90 or greater for CFI and TLI, and values less than 0.08 for RMSEA. P-values less than 0.05 were considered statistically significant.

Sample Size Justification
Sample size estimation of independent-samples-test was conducted using G * Power software packages, using a Cohen's small effect size of 0.2 at the power of 95% [34,35]. After factoring a 15% attrition rate (n = 163), the minimum sample required was 1247 participants. For the purpose of structural equation analyses, a minimum sample size of 300 was determined to be acceptable, as indicated by previous studies [36].

Results
A total of 1284 valid responses were included in the analysis. The mean age of the sample was 50.2 ± 18.1 years. Nearly 86% participants reported living in zip codes not touching an ocean or gulf area (Table 1). About 75 percent of the sample population reported having no college level education or degree. White respondents represented nearly half of the sample population. Six out of 10 respondents reported being employed and having an annual income under USD 100,000 (Table 1). About 13 percent of respondents had a history of skin cancer. Noticeably, 4 in 10 respondents had a family history of skin cancer (Table 1). Sunscreen users had a statistically significant higher mean scores for initiation (2.10 ± 1.49 vs 0.41 ± 1.2) and sustenance (1.82 ± 1.46 vs 0.36 ± 0.74) compared to sunscreen non-users ( Table 2).  Among participants who were engaged in sunscreen usage behaviors, the final model containing the demographic variables and all three constructs to predict initiation was statistically significant (adjusted R 2 = 0.736, F = 113.572, p < 0.001; Table 3). In the same group, constructs of emotional transformation, practice for change, and changes in social environment (besides family history of skin cancer) were significant predictors of the sustenance of sunscreen usage behavior (adjusted R 2 = 0.590, F = 59.565, p < 0.001; Table 3). Among participants who were not engaged in sunscreen usage behaviors, the model containing all constructs of initiation that were significant predictors of initiation was statistically significant; adjusted R 2 = 0.500, F = 61.305, p < 0.001; Table 4. In the sustenance model, emotional transformation, practice for change, and changes in the social environment explained 23.9% of variance in sustaining sunscreen usage behaviors among those who did not engage in sunscreen usage behavior (adjusted R 2 = 0.239, F = 19.80, p < 0.001; Table 4).

Construct Validation through Structural Equation Modeling
The structural equation modeling results (e.g., χ 2 [252] = 1511.870 (p < 0.001), CFI = 0.93, TLI= 0.92, and RMSEA = 0.08) for the initiation model demonstrated the goodness of fit of the data. Standardized effects of latent variables on the factor loading indicators were observed. The factor loadings of all the subscales of initiation are shown in Figure 2.

Discussion
The purpose of this study was to identify the correlates of sunscreen use, based on the fourth-generation multi-theory model (MTM) of health behavior change among Florida residents. MTM has been tested or applied to explain various health behaviors in community settings [37][38][39][40][41][42][43]. The results of the study were encouraging; the contribution of MTM constructs in all four models tested were significant and accounted for a substantial proportion of variance in the dependent variables. In our sample, 40.7% of the The sustenance model fit the data well (e.g., χ 2 [30] = 193.871 (p < 0.001), CFI = 0.98, TLI = 0.97, and RMSEA = 0.07). The factor loadings for emotional transformation, practice for change, and changes in the social environment were statistically significant. The factor loadings for all the subscales of sustenance are shown in Figure 3. The between construct correlations and standardized regression coefficients for emotional transformation showed moderate direct effects on the sustenance of sunscreen behavior, with β ranging from 0.12 to 0.51. However, both practice for change and changes in the social environment did not have any significant effects on the sustenance of sunscreen use behavior.

Discussion
The purpose of this study was to identify the correlates of sunscreen use, based on the fourth-generation multi-theory model (MTM) of health behavior change among Flor-

Discussion
The purpose of this study was to identify the correlates of sunscreen use, based on the fourth-generation multi-theory model (MTM) of health behavior change among Florida residents. MTM has been tested or applied to explain various health behaviors in community settings [37][38][39][40][41][42][43]. The results of the study were encouraging; the contribution of MTM constructs in all four models tested were significant and accounted for a substantial proportion of variance in the dependent variables. In our sample, 40.7% of the respondents used sunscreen, which was higher than the national rate of 31.5% [21]. However, sunscreen behavior was still low, given the second highest rate of skin cancer in Florida [4,5]. Understanding the determinants of sunscreen behavior is an important first step in promoting sunscreen usage behavior.
In the group who indicated sunscreen usage, all three MTM constructs (participatory dialogue, behavioral confidence, and changes in the physical environment), along with gender, race, and a history of skin cancer, were found to be significant predictors. This accounted for 73.6% of the variance in the initiation of the use of sunscreen, which is substantive in behavioral and social sciences [30]. Likewise, for sustaining sunscreen behavior among those who were already using sunscreens, all three constructs of MTM (emotional transformation, practice for change, and changes in the social environment) were found to account for 59.0% variance in the continuation of sunscreen usage. Moreover, all three constructs of MTM (participatory dialogue, behavioral confidence, and changes in the physical environment), along with gender and race, were significant explanatory variables for initiating sunscreen usage behavior among those who were not currently using sunscreen and accounted for 50% of the variance in initiation. Equally important was the finding that all three constructs of MTM (emotional transformation, practice for change, and changes in the social environment), along with gender and race, significantly accounted for 23.9% of the variance in the intention to maintain sunscreen usage behavior. These findings lend support to MTM as a strong model for designing, implementing, and evaluating sunscreen promotion interventions in the general population.
Consistently with previous studies, males were less likely to initiate use of sunscreens, both among those who were sunscreen users and those who were not. Holman and colleagues (2018), in their national study with 31,162 respondents, found that 22.1% of men compared to 40.2% of women used sunscreens [21]. Gender differences associated with intentional UV exposure through indoor tanning were also studied by previous reports [44][45][46]. In a U.S. based study, a higher proportion of females reported using indoor tanning compared to their male counterparts; however, data describing the setting (indoor or outdoor) of sunscreen use were insufficient [44][45][46]. Another interesting finding of our study was that history of skin cancer was positively associated with initiation of sunscreen usage behavior among those who were sunscreen users, but was not significant among those who did not use sunscreens. This could be explained by the reasoning that non-users were not concerned as much about their getting skin cancer or did not have "cues to action." The MTM can play a vital role in motivating this group of non-users. This finding provides additional support for designing sunscreen promotion interventions based on MTM. Another intriguing finding was that family history of skin cancer was a positively associated significant factor for both initiation and sustenance of sunscreen usage among those who were sun screen users, indicating that users were indeed convinced of the benefits of wearing sunscreens. These findings provide the basis of developing MTM-based interventions to promote sunscreen use.

Strengths and Limitations
To our knowledge, this was the first study to apply MTM to explain sunscreen usage behavior. We collected data on a multitude of correlates and adjusted for those in our analysis to generate robust estimates. Despite these strengths, this study is not without limitations. First, the use of a cross-sectional design has the limitation of collecting information on independent variables and dependent variables at the same time, thereby precluding causal inferences. Future studies could test the validity of MTM in experimental designs, whereby actual manipulation of the variables is done in a longitudinal manner. Furthermore, self-reports are liable to several shortcomings, such as dishonesty, exaggerated responses, and so on. However, when measuring attitudes, one cannot choose another approach and these are indeed the only means. Finally, the study was done in Florida, thereby limiting the generalizability to other parts of the country.

Implications for Practice
The MTM offers a valuable prototype to design efficacious and effective sunscreen promotion interventions. Such interventions can be delivered in community settings, such as through recreational centers, faith-based organizations, community centers, communitybased organizations, beach clubs, and other such venues. The promotional interventions could take the form of media campaigns; social media campaigns; one to one health education interventions, as well as in group forums; events and fairs; m-health interventions; counseling at clinics and patient care settings; and policy level efforts. For promotional interventions, the construct of participatory dialogue can be mobilized by underscoring the advantages, such as appeals to health, prevention of skin cancer, having peace of mind, not getting sunburn, and so on. At the same time, misperceptions about the disadvantages, such as staining, inconvenience, forgetfulness, cost, etc. can be clarified through discussion. The construct of behavioral confidence can be built through discussions on building assurance through self-reflection and other sources and overcoming potential barriers. The construct of changes in the physical environment can be developed through looking into the possibility of making sunscreen available to those who cannot afford it, discussing methods of application during travel and also looking into mobilizing policy support in this direction. Regarding the maintenance constructs, for emotional transformation, learning to identify feelings must be the first step in educational interventions. Then ways of converting these feelings, especially those that are negative, along with self-motivation and overcoming self-doubt must be undertaken. Regarding the practice for change construct, methods of monitoring sunscreen application behavior through apps or simple record keeping in a diary should be discussed. Troubleshooting lapses in practice and remedies must also be discussed. Finally, ways to mobilize support from family, friends, social media, health professionals, etc. must be discussed.

Conclusions
This was the first study undertaken to study the determinants of sunscreen usage behavior, using the fourth-generation, multi-theory model (MTM) of health behavior change. All the constructs of MTM were found to be significant predictors of sunscreen use among Floridians, thereby lending support to this model. All the constructs of MTM are modifiable, making it a practical approach for effecting behavior change. This study provides preliminary data to develop and test theory-based interventions to promote sunscreen usage among Florida residents.