Spanish validation of the simple lifestyle indicator questionnaire: validity and reliability analysis

Introduction It has been shown that lifestyle is a highly modifiable determinant having a direct effect on the health status. Therefore, short and simple questionnaires assessing the lifestyle of the general and clinical population are needed to create interventions on behavioral aspects that can improve the health status. The Simple Lifestyle Indicator Questionnaire (SLIQ) is a validated health scale in English that combines five lifestyle factors: diet, exercise, alcohol consumption, tobacco use, and stress level. The objective of this study was to validate the SLIQ questionnaire in Spanish by analyzing the scale’s validity and reliability. Its discriminatory power of the scale was also examined by evaluating the differences in health outcomes according to the levels of adherence to a healthy lifestyle. Methods The sample consisted of 745 participants with an average age of 39.94 (SD: 16.99). A transcultural adaptation process was carried out to validate the SLIQ questionnaire in the Spanish context, to determinate the structural equivalence of the Spanish version as compared to the English version, and to assess the psychometric properties of the scale. PREDIMED and IPAQ scales were used to analyze the convergent validity of the Spanish version of the SLIQ regarding to diet and exercise, and the questionnaires SF-12 and DASS-21 questionnaires were used to assess the capacity of the Spanish version of the SLIQ to discriminate health status related to different levels of reported lifestyles. Results Regarding validity, the results indicate significant correlations between the different dimensions of the SLIQ questionnaire and those used as a reference. As for reliability, the test–retest analyses reveal a high temporal consistency for the scores obtained on the questionnaire. Finally, the differences found in anxiety, depression, and quality of life, with regard to the different levels of adherence in the SLIQ questionnaire, suggest that the questionnaire’s Spanish version has adequate discriminatory power. Discussion The obtained correlation coefficients between the SLIQ and the other standardized measures pointed out the adequate convergent validity of the instrument. Moreover, the test–retest results demonstrated the stability of the results obtained through this questionnaire. Finally, the lifestyle categories derived from the SLIQ showed a high ability to discriminate between participants’ health profiles. Hence, it can be concluded that the Spanish version of the SLIQ questionnaire is a valid and reliable tool for the quick and effective assessment of lifestyle.


Introduction
Lifestyle (LS) is a concept referring to a person's behaviors, from both an individual point of view and in terms of group relationships, built around a series of common behavioral patterns (1).These habitual patterns of behavior characterize a person's way of life and may affect their health to a greater or lesser extent (2,3).According to the World Health Organization (WHO), these behavioral patterns are constantly being interpreted and tested in different social situations and, therefore, they are not constant, but rather, they are subject to change (4).LS includes behaviors such as eating, exercising, resting, sleeping, playing, socializing, and working, as well as other aspects; in other words, it refers to an individual's way of living (3,(5)(6)(7).The specific characteristics of LS may change over an individual's life, although certain habits or customs may remain the same over time (5,8,9).It has frequently been shown that a significant relationship exists between LS, health, and quality of life (10)(11)(12)(13).
Different studies have revealed that an unhealthy LS characterized by the use of tobacco, alcohol, and drugs, a lack of physical exercise, and unhealthy eating habits, is related to a series of pathologies such as dementia, cancer, type 2 diabetes, metabolic syndrome, and cardiovascular problems, among others (14)(15)(16).Numerous studies have found that a healthy LS is associated with a lower risk of cancer, cardiovascular disease, diabetes, and mortality, leading to a longer life expectancy and a more years of life free of these diseases (17)(18)(19)(20)(21)(22).These findings suggest that the promotion of a healthy LS could help ease the burden of medical care by reducing the risk of developing multiple chronic diseases and increasing disease-free life expectancy.Therefore, to ensure a longer and better quality life, measures promoting an active and healthy LS should be implemented, paying special attention to the adoption of habits fostering quality of life (23)(24)(25)(26).
Despite the abundance of scientific evidence revealing that maintaining a healthy LS is one of the main conditioning factors affecting health status, few assessment tools permit the quick and effective identification of LS and also assess the main LS dimensions that have been associated with a decline in health status.However, there are numerous questionnaires that allow for individualized assessment of the risk factors related to LS (1,(27)(28)(29)(30)(31).However, these questionnaires may be timely to complete and they may require a lot of very detailed information.This is a significant limitation both in terms of human and time resources with respect to their systematic use, especially in the field of healthcare (27).
Therefore, short and easy questionnaires that assess the LS of the general population and that may also be applied to the clinical and research field are necessary (27,28).The Simple Lifestyle Indicator Questionnaire (SLIQ) is a validated English language health scale consisting of 12 items that assess five factors of LS: diet, exercise, alcohol consumption, tobacco use, and stress level.Moreover, the scale provides a global score for LS and a score for each of its components and is quick to complete (27,28).The original English version of this questionnaire displayed adequate psychometric properties in terms of validity and reliability (6,27).
Different studies have used this tool to analyze the relationship between LS and different variables, including the recent study by Znazen et al. (32) relating LS and stress induced by home confinement during the COVID-19 pandemic.Other studies have also used the SLIQ questionnaire to analyze the association between adherence to an unhealthy LS and an increase in chronic diseases, especially cardiovascular ones (16,25,(33)(34)(35), or between the adoption of inadequate LS patterns and higher levels of stress, anxiety, and depression (36,37).
Considering the advantages of this questionnaire ease of application and good psychometric properties, the objective of this study is to validate the SLIQ questionnaire in Spanish and analyze its psychometric properties, focusing specifically on reliability and validity.Moreover, the study also assesses the questionnaire's ability to discriminate between health results based on the cut-off points established in the questionnaire to determine adherence to a healthy, intermediate, and unhealthy LS.

Design
This study is part of a large-scale cross-sectional study analyzing LS in the general population and its consequences on health and quality of life.An instrumental study of the validation of the SLIQ questionnaire in the Spanish context was carried out (38,39).Adaption of the SLIQ instrument to the Spanish context was performed in two phases.Firstly, in phase 1, a standard translation and back-translation process was carried out for linguistic validation.Then, in phase 2, the psychometric properties of the Spanish language instrument were evaluated, assessing both validity and reliability as well as the tool's discriminatory power regarding health outcomes, specifically anxiety, depression, and health-related quality of life.

Participants
Participants were selected using a snowballing technique carried out with the general population.
For eligibility to participate in the study, the following inclusion criteria must be met: (i) to have good reading comprehension in Spanish, (ii) to be of legal age, (iii) to have signed the informed consent form prior to participation.
The sample size consisted of 745 participants.The average age of the participants was 39.9 years old (SD = 16.99), and 67.1% were women (32.9% men).The rest of the sociodemographic data is shown in Table 1.

Sociodemographic data
An ad hoc questionnaire was used to collect the sociodemographic and clinical data.The following sociodemographic data were collected: age, gender, weight, height, nationality, place of residence, information on the individuals with whom the participant resides, education level, working situation, monthly household income, and civil status.

Lifestyle
For the assessment of LS, the Spanish version of the Simple Lifestyle Indicator Questionnaire (SLIQ) was used (27).As previously mentioned, this questionnaire assesses LS among the general population.It consists of 12 items grouped into five dimensions: three for Diet, three for Exercise, three for Alcohol consumption, two for Tobacco use, and one for Life Stress.Each item in each dimension is scored separately on a scale from 0 to 5 for Diet, 0 to 4, 0-8, and 0-12 for Exercise, 0 to 2 for Tobacco use, 1 to for Life Stress, and with no range for Alcohol consumption.However, these scores are grouped

Diet
The PREDIMED (40) questionnaire assesses adherence to the Mediterranean Diet (MD).This questionnaire consists of 14 items with a dichotomous response scale (0 or 1).The total PREDIMED score ranges between 0 and 14 points: higher scores are indicative of a higher level of adherence to the MD.One point is given when an individual's responses to each item on the questionnaire are characteristic of the MD (for example, the use of olive oil as a main source of fat in cooking) (40).

Physical activity
The short version of the International Physical Activity Questionnaire (IPAQ) questionnaire (41), consisting of seven items, assesses Physical Activity (PA) by recording walking time, sitting time, and the frequency, duration, and intensity of the exercise performed over the past 7 days.Specifically, this questionnaire assesses three properties of Physical Activity: intensity (light, moderate, or vigorous), frequency (days per week), and duration (time per day).According to the results, Physical Activity Level (PAL) is categorized as either "low, " "moderate, " "or high" (41).

Depression, anxiety, and stress
The short-form version of the Depression, Anxiety, and Stress Scale (DASS-21) (42) assesses the presence and intensity of depressive symptoms, anxiety, and stress experienced over the past week.For this, each of the three scales contains seven items, assessed on a 4-point Likert scale ranging between 0 ("It has not happened to me") and 3 ("It has happened to me a lot of the time, or most of the time").The final score is calculated from the sum of the items of each scale, with a minimum total score of 0 points and a maximum of 21.A score above 11 indicates severe depression, a score above 8 indicates severe anxiety, and a score above 13 indicates severe stress (42).

Health-related quality of life
The 12-Item Short Form Health Survey (SF-12) (43), validated with the Spanish population (44), is an instrument used to assess the quality of life of the general population.This instrument consists of 12 items and 8 dimensions: general health, physical functioning, physical role, emotional role, bodily pain, social functioning, mental health, and vitality.Using these 8 dimensions, two additional components are created: a Physical Health Component (PHC) and a Mental Health Component (MHC).The total score of the scale ranges from 0 ("worst health status") to 100 ("best health status").

Linguistic validation
In the process of translation-back translation and linguistic validation of the SLIQ questionnaire, a direct conceptual translation was performed from the original English version of the SLIQ into Spanish.Subsequently, a bilingual translator, unfamiliar with the original SLIQ instrument, translated the first Spanish version into English using a blind back-translation process.In the third step, a third unbiased translator compared the back-translated translation with the original version to check the linguistic equivalence while considering cultural differences.Here, minor changes were introduced such as the elimination of sports that are not practiced or that are practiced by a very small minority in Spain and therefore, are not well known (e.g., curling), the introduction of equivalences when some specific food products are referred (e.g., Raisin Bran), and specific changes regarding measures in the case of alcohol (e.g., oz. was replaced by ml).Finally, a committee consisting of four Spanish experts in LS assessment ensured the cultural and linguistic accuracy of the translated questionnaire.In terms of the instrument's interpretability, a total of 20 cognitive interviews were conducted, in which the questionnaire's pilot version was administered to the general population: 10 men and 10 women.
A psychologist trained in the assessment of health results collaborated in the interviews.Participants were asked to read the questionnaire aloud, fill it out, and indicate whether they understood or had any doubts about the meaning of the previous instructions, the items, and the alternative answers.When difficulties arose in reading comprehension, the interviewer helped the participant by clearly reading each item aloud.Finally, they were asked for an overall assessment of the specific instrument.There were no difficulties with understanding any of the items and all of them were adequately assessed by the interviewees.Therefore, none of the items were modified and the final version of the questionnaire was obtained in Spanish.The Spanish version of the SLIQ is included in Table 2.

Assessment procedure
The study was approved by the University of Alicante Research Ethics Committee (UA-2020-11-20) following the recommendations established in the Ethical Principles for Medical Research Involving Human Subjects (45).All participants were informed of the study objective and the confidentiality of the data collected, and prior to their participation, they signed an informed consent form, explaining that their authorization could be withdrawn or canceled at any time.
To administer of the questionnaires, a completely anonymous, and confidential online assessment protocol was created, including an information sheet about the study, informed consent for participation, and the distinct assessment instruments collected in the project.All of the questionnaires were administered in Spanish and all participants (n = 745) completed the full set of questionnaires included in the evaluation protocol: SLIQ, PREDIMED, IPAQ, DASS-21, and SF-12.A non-probabilistic sample was used, selected using the "snowball sampling" technique.In this technique in the first phase of the study, participants who are representative of the target population are identified, requesting their collaboration to invite others with the same characteristics to participate in the study (46).This technique, widely used in biomedical and behavioral science research studies, has obtained good results as it permits access to a representative and relevant sample of the target population, while simultaneously reducing costs (in terms of both time and money) (46).
The degree of consistency and stability of the scores obtained from the SLIQ questionnaire was verified through a test-retest procedure.To this end, the Spanish version of the SLIQ was administered twice to a random selection of representative individuals of the obtained sample (n = 101) with a six-month time interval between the test and retest.This procedure permits the analysis of the degree of stability of the test over time and, thus, allowed for the quality of the data obtained to be verified.

Statistical analysis
Descriptive and frequency statistical analyses were used for data analysis.In addition, correlational analyses were conducted to establish associations between the variables analyzed, such as Pearson-type correlations and intraclass correlations.Based on the scores obtained in SLIQ, participants were divided according to the original cut-offs into three groups, depending on the quality of their lifestyle: unhealthy (n = 113), intermediate (n = 408), and healthy (n = 224).With the objective of establishing the differences between groups regarding depression, anxiety, stress and health-related quality of life (HRQoL), uni-or multivariate ANOVAs were performed.Statistical significance was established at p < 0.05.All analyses were carried out using the JASP statistical package (Version 0.16.3).

Scores in each item and dimension of SLIQ
Table 3 shows the scores obtained for each item included in the SLIQ scale.In addition to the descriptive score of the five dimensions included in the SLIQ scale, Table 4 shows the score categorization including the percentage of participants within each category.The total questionnaire score is also categorized in this table.

Convergent validity
Table 5 shows the correlations of the diet, exercise, and stress dimensions of the SLIQ questionnaire with their reference standards: the PREDIMED questionnaire for Diet, the IPAQ questionnaire for Exercise, and the Stress subscale of the DASS-21, respectively.In all cases, the correlations are significant.

Test-retest reliability
The intraclass coefficient correlation (ICC) for repeated measures in the SLIQ questionnaire was 0.836 (p < 0.001) for the total diet score, 0.921 (p < 0.001) for exercise, 0.978 (p < 0.001) for alcohol consumption, 1.000 for tobacco use, 0.825 (p < 0.001) for stress, and 0.923 (p < 0.001) for total healthy lifestyle score.According to the literature, this indicates good to excellent agreement.
The test-retest reliability for the different items of the scale ranged from 0.718 for fiber consumption to 1.000 for tobacco use item, respectively (Table 6).

Differences regarding levels of depression, anxiety, and HRQoL as a function of lifestyle
To identify the discrimination power of the Spanish version of the SLIQ on health outcomes, the differences in HRQoL, anxiety, depression and stress based on the level of adherence to a healthy LS were evaluated.Hence, participants were initially classified into three groups according to their scores on the SLIQ questionnaire for LS ("unhealthy, " "intermediate, " and "healthy") (Table 7).
In the case of HRQoL, differences between groups were found in physical functioning (PF) [F( 2 Differences between the three groups were revealed after the posthoc analysis was performed, revealing differences between participants with high adherence to a healthy LS as compared to those with low adherence (p < 0.05).No significant differences were found in the analyses for physical role (PR) and the Physical Health Summary Score (p > 0.05).

Discussion
The aim of this study was to carry out the transcultural adaptation of the SLIQ questionnaire to Spain and validate it.This is a short and easy-to-apply instrument that provides a global lifestyle score, as well as specific scores for each of its components.After analyzing the data, the results appear to indicate that the Spanish version presents adequate psychometric properties to assess the LS of the general population.Regarding the translation process and the transcultural adaptation of the questionnaire, the results show an adequate frontiersin.orgequivalence between both the English and Spanish items, which apply to the Spanish context without the need for further modifications.Regarding psychometric properties, to assess the convergent validity, associations between the SLIQ dimensions and different standardized referral questionnaires were analyzed.Statistically significant correlations were obtained from these analyses, which were similar to those obtained in the study by the authors of the original scale (6).Specifically, in the study by Godwin et al. (6), the correlations between the dimensions of diet and alcohol consumption from the SLIQ questionnaire and the scores from the Diet History Questionnaire were analyzed, obtaining r = 0.679 and 0.665, respectively (6).Regarding physical activity, a pedometer was used to measure the number of steps taken over 3 days and correlate it with the scores of the exercise dimension of the SLIQ questionnaire, obtaining r = 0.455 (6).Stress was another variable used by the authors of the original scale to assess convergent validity.It was measured using the Social Readjustment Rating Scale, obtaining a score of = −0.264(6).Finally, with regard to concurrent validity, the eightquestion scale on cardiovascular risk by Spencer et al. (47) was assessed, obtaining a reasonable correlation (r = 0.475) (47).In this study, the diet, exercise, and stress variables were correlated through the IPAQ and PREDIMED questionnaires and the stress dimension of the DASS-21 questionnaire, respectively.The correlation coefficients of diet, exercise, and stress analyzed in this study were 0.466, 0.490, and −0.369, respectively, thus displaying a significant relationship (p < 0.01).Although the size of the obtained correlation coefficients was smaller than expected and lower in comparison to the previous studies indicated above, the results demonstrate that the Spanish version of the SLIQ questionnaire may be a valid instrument for the assessment of different LS dimensions, having significant associations with scores obtained in other standardized instruments considered the gold standard for the assessment of the same variables.
Moreover, the SLIQ questionnaire has been shown to have good test-retest reliability.Test-retest reliability was determined by calculating the ICCs (48).The ICC results were obtained between the first and second measurements of the SLIQ questionnaire for the total score of each scale item; the total score of the five dimensions (Diet, Exercise, Alcohol consumption, Tobacco use, and Stress); and the total healthy lifestyle score.General guidelines for clinical research were used to establish the criterion to define the correlation strength, with a correlation below 0.25 indicating little or no agreement, a correlation between 0.25 and 0.50 indicating some agreement, a correlation between 0.50 and 0.75 indicating moderate to good agreement, and a correlation above 0.75 indicating good to excellent agreement (49).Finally, to analyze whether the questionnaire would permit the identification of LS profiles that may discriminate the health status of the population, the differences regarding HRQoL, depression, anxiety, and stress were analyzed among individuals in the unhealthy, intermediate, and healthy lifestyle groups.Differences were found for the SF-12 questionnaire in the dimensions of physical functioning, bodily pain, general health, vitality, social functioning, emotional role, mental health, and the mental health summary score.Regarding the DASS-21 questionnaire, these differences were found in the anxiety, stress, and depression dimensions, suggesting that an unhealthy lifestyle is related to higher levels of anxiety, stress, and depression.Likewise, for the SF-12 questionnaire, with the exception of the dimensions of the physical role and the physical health summary score, the other dimensions showed significant differences between the groups.These results are in line with those from past studies, which found that individuals with lifestyles having more health risk factors obtained lower scores on health-related quality of life (50,51).Among the lifestyle risk factors, special note should be made of alcohol consumption, tobacco use, stress, unhealthy diet, and lack of physical activity (52)(53)(54)(55).Likewise, as in this study, the ASPREE work (56) revealed differences in quality of life depending on the population's lifestyle, with those consuming less alcohol and leading a more active life obtaining higher scores on the physical and mental components, while smokers obtained worse results in the physical component, implying a poorer quality of life (56).Many studies show that regular physical activity and a healthy diet improve HRQoL and well-being (57,58).However, alcohol consumption and tobacco use, as well as high stress levels, are related to a poorer quality of life, having a great negative impact on HRQoL (59)(60)(61).Likewise, a healthy LS can contribute to the prevention of health diseases, especially chronic and cardiovascular ones (23,33,35).As a result, the SLIQ questionnaire has been shown to be valid and reliable for identifying differences in LS and its relationship with health outcomes.

Limitations
The results of this study demonstrate the reliability and validity of the SLIQ questionnaire for its use in Spain.Although this represents an advance in the validation of short, valid, and reliable instruments for their use in different clinical and research contexts, some study limitations should be mentioned.Firstly, it is worth noting that the questionnaires were self-reported, which may imply certain comprehension biases and, therefore, could alter the results.Moreover, fewer participants agreed to take part in the retest, and other variables that may have influenced the results of the retest, such as health literacy, were not evaluated.Additionally, the possible differences in SLIQ results between participants from urban versus rural contexts have not been considered in the present study due to comprehension biases or difficulties in completing self-report measures.Future studies should use longitudinal methodologies with larger sample sizes to corroborate the results of this work.

Conclusion
It has been shown that LS is highly related to the population's quality of life and well-being.It also serves as a protective factor against the development of different diseases.Therefore, most studies analyze health risk factors in an individualized manner, with fewer studies undertaking a global analysis, including diet, exercise, alcohol consumption, tobacco use, and stress, through short, valid, and effective instruments.The results obtained in this study show that the Spanish version of the SLIQ questionnaire is a reliable instrument for the assessment of the population's lifestyle and, therefore, they show that its use by both clinics and researchers would provide fast, valid, and highly reliable results on the population's LS.

TABLE 1
Sociodemographic data of the participants.

TABLE 3
Descriptive scores of the items of the SLIQ scale.

TABLE 4
Descriptive scores of the categories of the SLIQ scale.

TABLE 5
Analysis of convergent validity between the dimensions of the SLIQ and referent questionnaires.

TABLE 6
Intraclass correlation coefficients (ICC) between the first and second measurements of the SLIQ scale.
According to the previous correlation strength criterion, only two items (fiber consumption and light exercise) from the SLIQ questionnaire obtained a score of moderate to good with a score of 0.718 and 0.734, respectively.The rest of the items obtained a correlation above 0.75, confirming that the SLIQ questionnaire has a good level of test-retest reliability; and therefore, the temporal stability of the scores was shown to be adequate.Moreover, observing the sociodemographic data of participants who agreed to participate in

TABLE 7
Differences regarding levels of depression, anxiety, stress, and HRQoL as a function of lifestyle.theretest, an equivalence regarding the sociodemographic profile obtained in the first administration of the test is confirmed.This reinforces the stability and reliability of the test, regardless of the respondent's sociodemographic profile.