Personal values in adolescence and their associations with metabolic biomarkers in adulthood: a population-based study in Japan

Background : Personal values, which are formed in early life, can have an impact on the health outcome later in life. Objective: The aim of this study is to investigate the relationship between personal values in adolescence and bio-indicators related to metabolic syndrome (MetS) in adulthood. Participant and Methods : The longitudinal data was used from the Japanese Study on Stratication, Health, Income, and Neighborhood (J-SHINE) in 2012 and 2017. Personal values in adolescence were retrospectively obtained in 2017 from a self-reporting questionnaire, composed of value priorities and commitment to the values. Venous samples were collected in 2012 for low and high-density lipoprotein (LDL, HDL) cholesterol and hemoglobin A1c (HbA1c). Body mass index (BMI), waist circumference and systolic and diastolic blood pressure (SBP, DBP) were also measured. The associations of each variable were examined by partial correlation analysis. In addition, multiple linear regression analysis was conducted to examine overall associations between personal values and the sum of standardized scores (Z-score) of the biomarkers as a proxy of MetS. Furthermore, cluster analysis was conducted to identify groups of the participants who have some specic values and to examine their associations with the Z-score. Results : The total population (n=668) included 261 men and 407 women. Among men, the personal value priority of “Having inuence on society” was associated with high HDL cholesterol (partial r=0.13, p=0.032) and “Cherishing familiar people” with low waist circumference (r=-0.129, p=0.049), low SBP, and high DBP (r=-0.135, p=0.039; r=0.134, p=0.041). In women, “Not bothering others” was associated with high SBP and low DBP (r=0.125, p=0.015; r=-0.123, p=0.017). "Economically succeeding" were associated with worse outcome (β=0.162, p=0.042). In the cluster analysis, both in men and women, the cluster which had highest openness to change value; “Having and keeping a belief”, “Exploring what you were interested in” and “Actively challenging” with the highest commitment showed worst proxy outcomes although there were no signicant differences. Conclusions : Although some signicant associations were found between personal values in adolescence and MetS-related markers in adulthood, overall associations were not strong. Culturally prevailing values were likely to be associated with a good outcome of metabolic health.


Introduction
Metabolic syndrome (MetS) recognizes risk factors of underlying cardiovascular and metabolic disease, characterized by comorbidity of abdominal obesity, high blood glucose or insulin resistance, hypertension, dyslipidemia and microalbuminuria (1). At least one-fth of the adult population is affected by MetS with an increase in prevalence in Asia (2). A recent meta-analysis showed that MetS was associated with a higher risk of all-cause mortality in the elderly (3). Early prevention of MetS is of critical importance in Japan, which is highly aged society. Obesity and overweight de ned by body mass index and waist circumference are especially important components of MetS in developing cardiovascular disease and cancer and elevating the risk of mortality (3,4). Therefore, detecting and intervening in the modi able risk factors for MetS in early life stage are important issues in medicine and epidemiology (5).
Previous studies have indicated that individual psychological and behavioral factors are associated with the components of MetS (6)(7)(8)(9). MetS is usually considered a re ection of individual lifestyle, such as insu cient physical activity, excessive stress, and unhealthy eating habits, all of which are matters of personal choice (5). For example, motivations for adherence to improving lifestyle and diet modi cation were key factors in the reduction of MetS components (6). Moreover, these factors have been associated with biomarkers (e.g., serum cholesterol, triglyceride, glucose) related to Mets. As an example of the important role of psychological factors in physical health, stress management is known to be a direct mediator of the link between stress and preferable biomarkers related to MetS through emotional and behavioral self-regulation (8).
Children and adolescents have become important targets of public health because individual healthrelated psychology and behavior are formed in early childhood (10). Previous review has indicated that early healthy practice can be protective for metabolic outcomes in adults (11,12). Psychosocial exposures in childhood, which much in uenced on creation of sense of value, can also be determinants of lifelong predilection to metabolic disease in adulthood (13)(14)(15)(16)(17)(18). There is an urgent need to explore the kind of psychological and behavioral factors in childhood and adolescence that affect the onset of MetS throughout the rest of the life course.
One such factor is personal value, which is supposed to develop in adolescence (19) and could affect health, well-being and the development of MetS in adulthood (20). Personal values consist of value priorities (21) and commitment to values (22). Personal value priorities, introduced by Schwartz (21), are a personal selection of important values. Value priorities are developed in adolescence and affect individual psychological and behavioral health, including personal choice for lifestyle and commitment to one's own health (9,20). In addition, commitment to values, which indicates how committed people are to living their values, is considered important (22). Behavioral commitment to values can be an intrinsic motivation and is known to have a positive relationship with greater well-being (23). Research on personal values in adolescence investigating the relationship with outcomes in adulthood have recently begun to be published (24).
However, it is still unknown how much impact personal values in early life have on the risk of MetS later in life. Ascertaining whether or not there will be a direct association between personal values and health outcomes might be useful in considering the importance of values in adolescence. It seems worthwhile to investigate the relationship between personal values in adolescence and bio-indicators related to MetS in adulthood. Elucidating this relationship would have practical implications for MetS prevention. Although the focus is now mainly on the high-risk adult population, considering personal values in adolescence may shift the target to an earlier life stage. To reveal the speci c association between personal value in adolescence and health status in adulthood possibly contribute to the prevention of MetS in Japan, highly aged society. This study investigates the association between personal values at age 15 with the biological markers related to MetS in adulthood. We explored and tested the interrelationships between value priorities and commitment to those values, and low-and high-density lipoprotein cholesterol, HbA1c, body mass index, waist circumference and blood pressure.
Participants And Methods

Study setting
This study was conducted by recall of personal values in adolescence, using longitudinal data from the Japanese Study on Strati cation, Health, Income, and Neighborhood (J-SHINE), which has been described in detail elsewhere (25). It was designed to investigate the complex associations between social factors and health. The ethics committee of the Graduate School of Medicine and Faculty of Medicine, The University of Tokyo approved this study. Consent for participation in the study and the agreement for publication was indicated by completing and returning the self-administered questionnaire.
Additional written informed consent was obtained for participants who undertook physiological measurements and serum samplings.
Study period and participants J-SHINE data was collected at three points: between July 2010 and February 2011 (wave 1), July and December 2012 (wave 2), and October 2017 (wave 3). Target participants were randomly extracted from the Basic Resident Register of adults aged 25-50 years old from four municipalities in Japan (two in the Tokyo metropolitan area and two in neighboring prefectures). Wave 1 sample sizes were 4357 (valid response rate: 31.3% = valid data (n=4357) / originally selected sample (n=13920); cooperation rate: 51.8% = valid data (n=4357) / accessible sample (n=8408)). Wave 2 captured n=2961, 69.0% of wave 1 participants. Researchers invited all 2961, who answered the wave 2 survey, to undergo physical measurement and serum sampling using a self-administered nger-prick blood sampling kit (Demecal Kit; Leisure Inc., Tokyo, Japan). A subpopulation that underwent biomarker measurements was 1205. N=2787 answered the questionnaire on Wave 3 (response rate = 64.9%). We used the data from waves 2 and 3. People who agreed to participate in the study completed a self-administered questionnaire using a computer-aided personal instrument (CAPI). People who were unfamiliar with computers sat for a personal interview according to the CAPI. Eligible participants offered physical data and a serum sample in the wave 2 survey and completed a questionnaire about personal values in adolescence in wave 3. Those who had incomplete data for these variables and confounders (age and education) in 2012 were excluded. The owchart of participant recruitment is shown in Figure 1.

Measurements
(1) Exposure -The Personal Value in Adolescence-Personal values in adolescence was developed based on Schwartz's theory of 10 basic values (21,26).
Although a scale for measuring personal values in Schwartz's theory was already developed, the scale has been used primarily for adults and not adolescents. The terms and constructs should be locally meaningful for adolescents (27). A research article that used this scale has already been published (24).
Personal values contain two components: value priorities and commitment to the values. Value priorities were measured by 11 items: economically succeeding, improving society, exploring interests, in uencing society, actively challenging, cherishing familiar people, graduating from a famous school, and maintaining a stable life. These items are rated on a seven-point Likert scale (1=Not at all to 7=Very important) following the question, "When you were 15-16 years old, how important did you think the following values were in your life?" Test-retest reliability was acceptable (0.556 to 0.729) when examined in another dataset in a 1-month interval, except for the value of "Cherishing familiar people (0.372)." Cronbach's alphas in the same sample ranged from 0.540 to 0.842. These 11 items can be possibly rede ned into Schwartz's four dimensions: Self-transcendence (universalism, benevolence); "Improving society" and "Cherishing familiar people". Conservation (conformity, tradition, security); "Not bothering others" and "Maintaining a stable life"; Openness to change (self-direction, stimulation, hedonism); "Having and keeping a belief", "Exploring what you were interested in" and "Actively challenging"; Selfenhancement (hedonism, achievement, power); "Being evaluated by others", "Economically succeeding", "Having in uence on society" and "Graduating from a famous school".
Commitment to the values was measured by the Personal Values Questionnaire II (PVQ-II) (22). The Japanese PVQ-II consists of eight items (e.g., How committed are you to living this value?). Each item is rated on a ve-point Likert scale. The internal consistency, concurrent, and structural validity have already been con rmed (28). In this study, we changed the items from the present to the past tense and instructed the participants to answer the items they had considered the most important when they were 15-16 years old. The sum of the PVQ-II scores was used for analysis; higher scores indicate greater commitment to the values. Test-retest reliability in 2 weeks in another dataset was 0.742, and Cronbach's alpha was 0.851.
(2) Outcomes -Biomarkers and physical health index-Primary outcomes in this study were important risk factors related to MetS and lifestyle-related disease. Venous samples were collected for low-density lipoprotein (LDL) cholesterol (mg/dL), high-density lipoprotein (HDL) cholesterol (mg/dL) and HbA1c (%, NGSP).
Body mass index (BMI, kg/m2) was calculated using the formula; weight (in kilograms) divided by height (in centimeters). Waist circumference (cm) was measured by a tape measure at the level of the umbilicus.
Auscultatory systolic and diastolic blood pressure (mmHg) were assessed with a mercury column before and one minute after standing three times. We took three measurements and used the average.
(3) Sociodemographic characteristics Sociodemographic variables included age and educational status (less than junior high school diploma, high school diploma, some college, more than university degree). These two covariates were used for adjusting in statistical analyses (partial correlation analysis and multiple linear regression analysis).

Statistical Analysis
First, partial correlation coe cients between the personal values in adolescence and the health outcomes in adulthood were calculated, adjusting age, educational status, marital status, working status, household income, and all other variables of personal values and biomarkers related to MetS. Second, to examine overall associations between personal values and biomarkers of MetS, a standardized score of a proxy of MetS (Z-score) was calculated by summing up standardized scores of each Mets-related marker, higher scores indicating adverse conditions. We used the Z-score as a dependent variable of multiple linear regression analysis. Statistical signi cance was de ned as p<0.05. All of the statistical analyses were performed using SPSS 26.0, Japanese version.

Post-hoc statistical power calculation
After conducting the multiple regression analysis, we calculated the post-hoc statistical power (1-beta) for the signi cant effects. Among men, the smallest and signi cant effect size was 0.015 increase of R2. As a result, the estimated post-hoc power (1-beta) was 0.51 when the total sample size was 261, if the effect size f2 was 0.015, assuming that the alpha was less than 0.05 (two-tailed), using the G*Power 3 program (29,30).

Results
The number of participants who were eligible in this study was 668 (261 men and 407 women) with no missing data on all variables used for analysis. The average age of 261 men and 407 women was 39.27 (SD=6.8) and 38.41 (SD=6.6) years old, respectively. The total population (n=668) was estimated to represent 15.3% of all participants in the J-SHINE cohort. Table 1 shows the descriptive characteristics of this study sample. The frequency distribution of variables showed an almost normal distribution. Compared to those who took biomarker survey but were dropped out from the analysis because of missing variables or not responding to wave 3 (n=537), the nal respondents (n=668) were signi cantly older (mean age, 36.37 and 38,74, respectively, p<0.001), more likely to be married (p<0.001), and had higher household income (p=0.020). There was no signi cant difference in sex, education status, work status, household income, BMI, waist circumference, SBP and DBP, serum LDL, HDL, or HbA1c between the two samples (data available upon request).
"Economically succeeding" were associated with worse outcome (β=0.162, p=0.042). Among women, personal value of "Graduating from a famous school" was signi cantly associated with better outcome in the crude model (β=-0.132, p=0.029) but was not signi cantly after the adjustment (β=-0.066, p=0.291). No signi cant associations were found after applying Bonferroni corrections.
-------------Insert Table 3 here -------------Discussion Some signi cant associations were found between the personal value priorities in adolescence and MetSrelated biomarkers in adulthood: among men, the personal value priority of "Having in uence on society" was associated with high HDL cholesterol and "Cherishing familiar people" with low waist circumference, low SBP and high DBP. In women, "Not bothering others" was associated with high SBP and low DBP. However, these associations regarding blood pressure were inconsistent and very weak, thus it is di cult to address the de nite meaning of this nding. As an overall composite indicator of MetS, "Being evaluated by others" was signi cantly associated with good outcome and "Economically succeeding" was signi cantly associated with worse outcome, even after adjusted all variables. The association was still blurry even when considering a cumulative impact of personal values in the cluster analysis. Personal values in adolescence may therefore not be strongly associated with biomarkers related to MetS.
Even though the association found was weak, but some personal values in adolescence certainly linked with metabolic biomarkers in adulthood in the present study. Possible mechanisms can be through behavioral and/or psychological pathways. One of the pathways may be a value-behavior-biomarker link. Personal values in adolescence could be related to forming health-related behaviors (31) in adolescence that would contribute to the development of MetS (6,7,(32)(33)(34). The other possible pathway is a valuepsychological factor-biomarker link. Previous research has suggested that unhealthy (or maladaptive) values may cause psychological distress as anxiety and depression (20), that could increase a risk factor for MetS (35). The association between personal values in adolescence and MetS in adulthood should be further investigated considering mediating roles of health-related behaviors and psychological distress. Because health-related behaviors and psychological distress may change over the life course that may weaken the observed association between personal values in adolescence and MetS in early adulthood, future research should incorporate time-variant covariates/mediators in the analysis.
Besides, the characteristics of each value which had signi cant association with biomarkers should be noted. "Having in uence on society" and "Cherishing familiar people" in men were associated with good outcome of HDL and waist respectively. Although the priority of V9 in men and V1 in women signi cantly in uenced blood pressure outcome, but the results were inconsistent. As a cumulative indicator related to MetS, among men, "Being evaluated by others" was related to healthy and "Economically succeeding" was related to unhealthy outcome. Among women, any value which had a provable association cannot be detected. Possible reasons could be how prevalent the values are among Japanese female and male populations: prevailing values in Japan might be establishing a good role for health. As previous research indicated, individuals may experience di culties if their value hierarchies are incongruent with the prevailing hierarchy in their social environments (36). Sagiv (2000) pointed out that consistency between peoples' value priorities and their cultural values is critical for well-being (20). Adaptive choice for preferable personal value may lead to good health by improving well-being (23). The results from our study seem to be consistent with these ndings. "Having in uence on society" and "Cherishing familiar people" in men, which were associated with better metabolic outcome, might be an acceptable value because values related to self-enhancement and self-transcendence are prevailing among men. This study has several limitations. First, our questionnaire was not the same as Schwartz's original (21). Second, there might be recall bias since this study adopted a retrospective design. Life events from adolescent to the time survey conducted could in uence on the recall of values in adolescent. Third, external validity might be limited because dropout rates were relatively high (wave 2; 31%, wave 3: 35.1%). Fourth, lifestyle and obesity at age 15 and adult, information that we did not collect in this study, might be a potential confounding factor. Time-variant covariates/mediators such as the alteration of behavioral and psychological factors were not considered. Fifth, estimated post-hoc power (1-beta) was low (0.51 in men). It might be possible that the association would increase with a larger sample size.
Sixth, su cient serum biomarker to meet the de nition of MetS, such as triglyceride, were not measured in this study. Lastly, there would be a possible effect of personality, which might be created antecedent to value. Some personality traits such as higher neuroticism and lower conscientiousness reportedly have been associated with greater risk of metabolic dysfunction from early life (9). High extraversion among men and low agreeableness among women are known to be related to obesity (37). Big ve personality consistently affects health-impairing behaviors and psychopathology (38,39). Though value and personality are consistent, a recent meta-analysis found theoretically predictable relationships among them, but the constructs are distinct (40). This study focused on personal values; however, it cannot be denied that personality traits in both adolescence and adulthood affected the association between value and MetS.
Despite these limitations, we have provided evidence that the presence of personal values in adolescence is an important concept for considering health outcome as an adult. Although the overall association was ambiguous, personal values in adolescence might be related to the risk of MetS. Future research would be needed to overcome the limitations of the current study, such as prospective design, using wellvalidated measurement scale of personal value, or obtaining comprehensive biomarkers to meet the criteria of diagnosis of MetS. Nevertheless, if the effect of adolescents' personal values on MetS is provided, two important policy/practice implications in public health would be stated;(1) education in childhood can be improved to include knowledge about the relationship between personal value and health;(2) clinical counseling based on personal value can be new effective approach for health promotion and prevention of MetS. Further evaluation may reveal the impact of personal values on health outcomes through a behavioral and psychological determination of health habits over the lifetime.

Conclusions
The study found no consistent strong pattern for the association between personal value priorities in adolescence and MetS-related biomarkers in Japan. However, culturally favorable values (i.e., cherishing familiar people) might be associated with future properties of biomarker related MetS in adults.

Availability of data and material
The dataset obtained from the J-SHINE cohort studies are not publicly available due to the consensus among researchers. Details of the questionnaire adopted in the J-SHINE surveys are available at http:// park.itc.u-tokyo.ac.jp/dhsb/project.html.

Competing interests
The authors declare that they have no competing interests.

Funding
The research was supported by grants provided by Grant-in-Aid for Scienti c Research on Innovative Areas (No. 21119002) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
Authors' contributions NK conceived the study. NS, KW and NK designed the method. NS and KW analyzed the data and wrote the rst draft. All authors interpreted results and approved the nal version of the report.  Table 3. Coefficient β and p-value for z-score as a proxy of MetS with sum of outcome in relation to personal value in adolescence variables.  A standardized score of proxy of Mets (Z-score) was calculated by summing up standardized scores of each Mets-related marker. High score indicated high-risk metabolic conditions. Figure 1 Flowchart of participant recruitment in J-SHINE.