Associations among skin carotenoids, anthropometric parameters and healthy lifestyle behaviors in young adults: a cross-sectional, population-based study

Abstract

Background

Healthy lifestyle behaviors are the cornerstone for the prevention of a wide range of metabolic and chronic non-communicable diseases (NCSs). Among lifestyle factors, diet, body mass index (BMI), smoking habits and physical activity are associated with the risk of developing NCSs, including obesity, type 2 diabetes, cardiovascular diseases and certain types of cancer. Particularly, as a part of a healthy diet, increased intake of fruit and vegetable (FV), rich sources of vitamins and minerals, dietary fiber and non-nutrient substances including antioxidants, are known to improve overall health. Carotenoid levels can be measured in skin providing an objective biomarker of long-term FV intake. This study aimed to explore the potential role of skin carotenoids as indicators of health status examining their associations with lifestyle factors among a cohort of young adults. This study aimed to explore the potential role of skin carotenoids as indicators of health status examining their associations with lifestyle factors among a cohort of young adults.

Methods

A sample of 2078 university students were enrolled at the University of Calabria, Italy. All participants underwent anthropometric measurements, assessment of the adherence to the Mediterranean Diet (MD) pattern by the Mediterranean Diet Adherence Screener (MEDAS) and Mediterranean Life Style Index (MEDLIFE) questionnaires and the skin carotenoid content by Veggie Meter®. Student’s t-test, chi-squared test, and univariate and multiple linear regressions were used for analyses.

Results

Participants had a mean BMI of 23.30 ± 3.79, which falls within the normal range as well as a medium adherence to the dietary (MEDAS: 7.19 ± 1.86) and lifestyle (MEDLIFE: 3.38 ± 1.21) MD patterns. Mean skin carotenoid levels were 360.61 ± 97.02, with higher carotenoid score in participants stocking up on FV from garden than market (368.28 ± 99.98 vs 357.84 ± 95.88, p = 0.03). Moreover, skin carotenoids were significantly higher in participants declaring to consume more than 2 servings of vegetables and more than 3 servings of fruits/day compared to those having less FV intakes (391.67 ± 101.03 vs 349.27 ± 90.92, p < 0.0001). Multiple regression analyses have revealed that the carotenoid score was positively associated with age, male gender, MEDAS, stocking up on FV from the garden and consuming high FV, while it was negatively associated with BMI and smoking habits.

Conclusions

Skin carotenoids are objective indicators of health status showing a positive association with the adherence to healthy diet and lifestyle behaviors among a cohort of young adults. Findings from this study may contribute to identify individuals with potential risk factors for NCDs and to develop public health strategies to encourage healthier lifestyles.

Introduction

Healthy lifestyle behaviors are the cornerstone for the prevention of a wide range of metabolic and chronic non-communicable diseases (NCSs). Among lifestyle factors, diet, body mass index (BMI), smoking habits and physical activity are associated with the risk of developing NCSs, including obesity, type 2 diabetes mellitus, cardiovascular diseases and certain types of cancer [1]. Particularly, as a part of a healthy diet, increased consumption of fruit and vegetable (FV) plays a crucial role in reducing the risk of several NCSs. Despite the recommendation of the World Health Organization on the importance to consume more than 400 g of FV per day [2], FV intake remains below the suggested levels in the population worldwide [2, 3]. In particular, young people, especially college students, are more likely to seek fast food and energy-dense takeaway meals, leading to a poor nutritional status and obesity-related disorders [4, 5]. Indeed, college students experience increased financial stressors along with limited work possibility due to the academic priorities, which lead to an unhealthy lifestyle. In Italy, it has been reported that only 44% and 22.5% of university students have at least 1 portion of FV per day, respectively. In addition, it has been found that Italian university students consume FV no more than 2–4 days/week [6], highlighting the need to increase their knowledge on healthy eating dietary pattern and to improve their dietary behaviors. The beneficial effects of FV depend on the presence of several bioactive compounds [7, 8]. Indeed, FV are a source of several macronutrients, including carbohydrates and proteins, as well as micro-nutrients and non-nutrients, such as minerals and vitamins. Among these compounds, carotenoids, naturally occurring fat-soluble pigments responsible for the red, orange, and yellow colors in various FV, play a particularly significant role in human health as very potent dietary antioxidants. They include β-carotene, lutein, zeaxanthin, and lycopene which exert protective actions against oxidative stress and inflammation, improving eye health, immune function and skin protection [9–12]. It has been demonstrated that the skin carotenoid levels correlate with individual plasma carotenoid species [13] and are positively associated with the FV intake, traditionally assessed by self-reported food questionnaires [14–16]. Assessing FV intake with an objective method, such as the measurement of skin carotenoids reduces the bias and inaccuracies associated with self-reported dietary questionnaires. Recently, the Veggie Meter® (Longevity Link Corporation, Salt Lake City, Utah), a non-invasive device based on spectrophotometric technology, has been developed to rapidly measure skin carotenoid levels [17]. It allows to evaluate long-term FV consumption, as skin carotenoid levels reflect the FV intake over approximatively two weeks, providing a more accurate assessment compared to short-term dietary recall methods. To date, the association between the skin carotenoid levels and the anthropometric characteristics and lifestyle habits is still under investigation. Understanding the relationship among FV intake, carotenoid levels and different confounding variables might provide valuable insights for developing tailored lifestyle strategies aimed to ameliorate health outcomes. The aim of this study was to estimate FV consumption measuring the skin carotenoid levels by Veggie Meter® and to evaluate their correlation with lifestyle habits in a cohort of young population. Findings from this study may contribute to the development of public health strategies to encourage healthier lifestyle behaviors among young adults.

Methods

Participants

This cross-sectional study was carried out among 2078 university students of University of Calabria, Italy, between March and June 2024, in the context of the MEDIET project. After an agreement with the course coordinator and lecturers, students from the first-year faculties were contacted in the classroom after lectures. They were asked to participate in this study voluntarily. Inclusion criteria were university students of 18 years of age or older enrolled into the first-cycle, second-cycle and third cycle degree programs (Doctoral studies and Specialization Schools), had Italian nationality and gave informed consent for participation. Subjects with liver diseases were excluded from the study. Moreover, to be included in this data analysis, after completing questionnaires to assess the adherence to the Mediterranean Diet (MD) pattern, students underwent to the measurements of anthropometric parameters and skin carotenoid levels. Respondents with any missing data were excluded from the study. Approval of this study was obtained from the ethic committee of the University of Calabria, Italy (Approval Number: #0735744/2023).

Assessment of adherence to mediterranean diet and lifestyle

We used a self-administered questionnaire on general and lifestyle habits which was adopted in previous studies [14, 18]. The questionnaire consisted of three different parts. The first part included questions on personal data, such as age, gender, education level, ethnicity and living circumstances, general habits, such as smoking status. The second part includes questions on eating habits and type of food commonly consumed in the Mediterranean area, recording the frequency of consumption of the food items in servings per day or week according to the validated 14-point Mediterranean Diet Adherence Screener (MEDAS) [19]. The third part included questions on healthy lifestyles for physical activity, rest, social habits and conviviality scored according to the validated Mediterranean Lifestyle Index (MEDLIFE) [20].

Anthropometric measurements and Skin carotenoid measurement

Weight and height were measured with subjects wearing light clothing and no shoes by trained personnel using a calibrated analogue scale. Participants’ weights were determined using the KERN MPC250K100 M scale, with an accuracy of 100 g and a load capacity of 250 kg. Height was determined using a Seca stadiometer, with an accuracy of 1 mm and a maximum capacity of 220 cm. BMI was calculated using the standard formula by dividing the body weight in kilograms by the square of height in meters [BMI = weight (kg)/height² (m)]. Using the standard cut points, the four BMI categories are as follows: < 18.5 kg/m² (underweight), 18.5–24.9 kg/m² (normal weight), 25–29.9 kg/m² (overweight) and ≥ 30 kg/m² (obese) [21]. Waist and hip circumferences of each participant were measured by trained personnel using Seca 201 measuring tape, with a range of 1 to 205 cm and a division of 1 mm.

Skin carotenoid levels were measured by the Veggie Meter® device (Longevity Link Corporation, Salt Lake City, Utah) on the index finger of the non-dominant hand of each participant after hand washing. Veggie Meter® scores range from 0 to 800, with higher scores indicating higher skin carotenoid content [14, 15].

Statistical analysis

Numerical variables are reported as mean ± SD, while categorical variables are shown as frequency (%). Comparisons of general characteristics and lifestyle habits between male and female participants were performed using Student's t-test for continuous variables and the Chi-square test for categorical variables. Additionally, one-way ANOVA, when appropriate, and Student's t-test with Holm-Bonferroni correction for multiple testing, were employed to assess differences in carotenoid skin content according to FV supply source and intake. The association between carotenoid score and collected variables was assessed using univariate and multivariable linear regression models. All statistical tests were two-sided, a p value < 0.05 was considered significant. All analyses were conducted using R (version 4.4.3).

Results

General and anthropometric characteristics of the study population

The study sample consisted of 2078 university students, aged 18–27 years old, who participated in the MEDIET project, and were included in the analysis. Participant characteristics, including age, gender, BMI and BMI categories, waist, hip and their ratio, smoking status are presented in Table 1. Over half of the participants were men (51.5%), with a mean age of 21.45 ± 2.16 years that was similar in women (21.37 ± 2.08). Overall, participants had a mean BMI of 23.30 ± 3.79 kg/m², fitting within the normal weight in the BMI classification range (18.5–24.9) for 66%, while 6.5% of subjects were underweight (< 18.5), 23% and 5.1% were overweight (25–29.99) and obese (≥ 30), respectively. As expected, a gender-related difference was observed in the anthropometric values, such as BMI, waist and hip circumference, and waist/hip ratio (p < 0.001). Interestingly, we found that the percentage of overweight and obesity in men was higher than in women (overweight: 30 vs 15; obesity: 6.7 vs 3.5, p < 0.001). Overall, 35% of students declared to be habitual smokers, including 38% men and 33% women (p = 0.017) (Table 1).

Table 1.

General and anthropometric characteristics of the study population

	Overall n = 2078	Men n = 1070 (51.5%)	Women n = 1008 (48.5%)	p value
Age (years) (Mean ± SD)	21.41 ± 2.12	21.45 ± 2.16	21.37 ± 2.08	0.379
BMI (kg/m2) (Mean ± SD)	23.30 ± 3.79	24.27 ± 3.83	22.27 ± 3.47	< 0.001
BMI categories (n, %)				< 0.001
< 18.5	135 (6.5%)	35 (3.3%)	100 (9.9%)
18.5–24.99	1361 (66%)	636 (60%)	725 (72%)
25–29.99	474 (23%)	324 (30%)	150 (15%)
≥ 30	106 (5.1%)	71 (6.7%)	35 (3.5%)
Waist circumference (cm) (Mean ± SD)	78.06 ± 10.37	83.96 ± 8.76	71.83 ± 8.02	< 0.001
Hip circumference (cm) (Mean ± SD)	97.70 ± 8.72	100.20 ± 8.35	95.06 ± 8.33	< 0.001
Waist/Hip ratio (Mean ± SD)	0.80 ± 0.07	0.84 ± 0.05	0.76 ± 0.06	< 0.001
Smoking status (n, %)				0.017
Smoker	735 (35%)	404 (38%)	331 (33%)
Non-smoker	1341 (65%)	662 (62%)	679 (67%)

BMI: Body Mass Index, SD: standard deviation

Adherence to the Mediterranean Diet pattern and skin carotenoid score of the population sample

Assessment of diet quality conducted on the total sample by MEDAS questionnaire revealed a medium adherence to the MD with a score of 7.19 ± 1.86, which was slightly higher in women than in men (7.28 ± 1.78 vs 7.11 ± 1.93, p = 0.046) (Table 2). According to MEDLIFE questionnaire, the total sample had a medium score (3.38 ± 1.21), which was statistically higher in men respect to women (3.58 ± 1.21 vs 3.18 ± 1.17, p < 0.001) (Table 2). About carotenoid content, the mean skin carotenoid content was 360.61 ± 97.02 in the entire sample, with significantly higher values in men than in women (381.89 ± 94.10 vs 338.16 ± 95.01, p < 0.001) (Table 2).

Table 2.

MEDAS, MEDLIFE and Carotenoid score in the total sample and by gender

	Overall	Men	Women	p value
MEDAS score (Mean ± SD)	7.19 ± 1.86	7.11 ± 1.93	7.28 ± 1.78	0.046
MEDLIFE score (Mean ± SD)	3.38 ± 1.21	3.58 ± 1.21	3.18 ± 1.17	< 0.001
Carotenoid score (Mean ± SD)	360.61 ± 97.02	381.89 ± 94.10	338.16 ± 95.01	< 0.001

SD: standard deviation

Next, we evaluated the skin carotenoids according to the daily consumption of FV. Noteworthy, we observed that students who daily consume less than two servings of vegetables and less than three servings of fruits (item #1: “Daily vegetable servings < 2 and Daily fruit servings < 3”) had the lowest values of carotenoid score (mean ± SD: 349.27 ± 90.92), while students who daily consume more than two servings of vegetables and more than three servings of fruits (mean ± SD, item #4: “Daily vegetable servings ≥ 2 and Daily fruit servings ≥ 3”) reached the highest level of skin carotenoids (mean ± SD: 391.67 ± 101.03 p < 0.0001). Stratifying by sex, the carotenoid score of item#1 and #3 was significantly higher in men than in women (mean ± SD, item#1: 372.63 ± 88.39 vs 323.03 ± 86.51, p < 0.001 and item#3: 401.59 ± 108 vs 359.94 ± 97.29, p < 0.001) (Fig. 1).

Fig. 1.

Carotenoid score in the overall sample and by gender according to the daily fruit and vegetable consumption. Boxes represent the median (central line) and interquartile range (IQR, box length), with whiskers extending to the smallest and largest values within 1.5 times the IQR. *p < 0.05 vs Vegetable < 2 and Fruit < 3 intake in overall participants, in males and in females

In addition, based on the FV supply, we observed that only 26.42% of students stocked up on them from the garden respect to 73.58% from the market. Skin carotenoid score was higher in participants consumed products from garden than from market (mean ± SD: 368.28 ± 99.98 vs 357.84 ± 95.88, p = 0.034) (Fig. 2). Again, gender differences were found in skin carotenoids with men having higher values respect to women in both garden (mean ± SD: 392.08 ± 95.91 vs 343.69 ± 97.88, p < 0.001) and market (mean ± SD: 378.26 ± 93.24 vs 336.13 ± 93.92, p < 0.001) suppliers (Fig. 2).

Fig. 2.

Carotenoid score in the overall sample and by gender according to fruit and vegetable supply. Boxes represent the median (central line) and interquartile range (IQR, box length), with whiskers extending to the smallest and largest values within 1.5 times the IQR. *p < 0.05 vs Market FV supply in overall participants and in males

Associations between carotenoid score and different variables in the population sample

Then, in our population sample, we performed univariate analysis evaluating the association between the carotenoid score and different variables, including general and anthropometric characteristics, consumption of FV, FV supply source, MEDAS and MEDLIFE. We found that the carotenoid score was positively associated with age (p < 0.001) and male gender (p < 0.001), while it was inversely associated with smoking status (p < 0.001). Interestingly, carotenoid levels were positively associated with consumption of ≥ 2 vegetable serving/day (p < 0.001), ≥ 3 fruit serving/day (p < 0.001) and FV supply at garden (p = 0.031). Regarding the adherence to healthy lifestyles, we also observed that carotenoids were positively associated with MEDAS (p < 0.001) and MEDLIFE (p < 0.001). Next, multiple linear regression analysis revealed that carotenoid score was significantly and directly associated with age (model 1–3: p < 0.001, model 4: p = 0.001), gender (men) (model 1–4: p < 0.001) and inversely associated with BMI (model 1: p = 0.003; model 2–4: p < 0.001) and smoking habits (model 1–4: p < 0.001) (Table 3). Moreover, in model 2 carotenoid score was significantly associated with vegetable daily intake (p < 0.001) as well as fruit daily intake (p = 0.006), while in model 3 in which FV supply source was added, we observed that skin carotenoid score was associated with vegetable daily intake (p < 0.001), fruit daily intake (p = 0.005) and FV supply source (p = 0.008). Finally, in model 4 carotenoid score was significantly and directly associated not only with FV supply source (p = 0.01) but also with MEDAS (p < 0.001) score (Table 3).

Table 3.

Multiple regression analyses among carotenoid score and different variables in our population sample

	Univariate		Model 1		Model 2		Model 3		Model 4
	β (CI 95%)	p value	β (CI 95%)	p value	β (CI 95%)	p value	β (CI 95%)	p value	β (CI 95%)	p value
Age (years)	3.9 (2; 5.9)	< 0.001	3.9 (2.0; 5.8)	< 0.001	3.6 (1.7; 5.4)	< 0.001	3.7 (1.8; 5.6)	< 0.001	3.1 (1.2; 5.0)	0.001
Females (vs Males)	− 43.7 (− 51.9; − 35.6)	< 0.001	− 48 (− 56; − 40)	< 0.001	− 50 (− 59; − 42)	< 0.001	− 50 (− 59; − 42)	< 0.001	− 49 (− 57; − 40)	< 0.001
BMI (kg/m2)	0 (− 1.1; 1.1)	0.9783	− 1.7 (− 2.8; − 0.56)	0.003	− 2.1 (− 3.2; − 1.0)	< 0.001	− 2.1 (− 3.2; − 1.0)	< 0.001	− 2 (− 3.1; − 0.89)	< 0.001
Smokers (vs Non-smokers)	− 20.5 (− 29.2; − 11.8)	< 0.001	− 22 (− 31; − 14)	< 0.001	− 20 (− 29; − 12)	< 0.001	− 21 (− 29; − 12)	< 0.001	− 19 (− 27; − 11)	< 0.001
≥ 2 Vegetable serving/day (vs < 2)	31 (21.9; 40)	< 0.001			31 (22; 40)	< 0.001	31 (22; 40)	< 0.001
≥ 3 Fruit serving/day (vs < 3)	26.2 (14.1; 38.4)	< 0.001			17 (4.9; 29)	0.006	17 (4.9; 29)	0.005
Fruit-vegetables supply at garden (vs Market)	10.4 (1; 19.9)	0.031					12 (3.3; 21)	0.008	12 (2.9; 21)	0.01
MEDAS	8.6 (6.3; 10.8)	< 0.001							8.3 (6.2; 11)	< 0.001
MEDLIFE	7.4 (3.9; 10.8)	< 0.001							3.3 (− 0.07; 6.6)	0.055
			Adjusted R2 = 0.073		Adjusted R2 = 0.10		Adjusted R2 = 0.102		Adjusted R2 = 0.101

BMI: Body Mass Index

Discussion

This study aimed to investigate the correlation between skin carotenoid levels and healthy lifestyle factors, including BMI, smoking habits, diet and lifestyle habits in a cohort of university students.

Recently, the measurement of skin carotenoids by Veggie Meter® has emerged as an objective method for estimating FV intake, preferable to the administration of food questionnaires subject to response bias and reflecting the total plasma carotenoid levels [14–16]. To further confirm the validity of the skin carotenoid content as a reliable biomarker of FV intake, we found the highest carotenoid score in participants consuming more than two servings of vegetables and more than three servings of fruits daily, giving the rationale to explore the association between skin carotenoids with potential modifiable health risk factors in order to identify carotenoids as a useful health biomarker.

High BMI, smoking status, unhealthy diet and sedentary lifestyle are associated with a higher incidence of NCD_S. Particularly, high BMI and obesity, which occur in the early twenties, reduced the potential disease-free years across adulthood [22, 23], suggesting that the body weight control in young adulthood might represent a strategy to prevent the onset of NCDs. Our population sample consisted of more than half normal weight participants, 23% overweight and 5.1% obese, showing a potential positive trend toward controlling body weight respect data from a previous national survey [24]. These data are encouraging and highlight that there is an increased awareness on the weight body management. In contrast, a negative result was observed in the smoking habits. Globally, the average rate of tobacco use among young people aged 25–34 years was 20.4% in 2022 [25], with Italy reporting 26.9% of smokers in the same age group in 2023 [26]. We found that the rate of smoking was 35% in our population sample, indicating that urgent national policy action is required to lower the smoking rates among the young population, despite the universal tobacco control strategies. In addition, using multiple regression analysis, we found that both BMI and the smoking status were negatively associated with the skin carotenoid levels in young adults. While the negative relationship between skin carotenoid score and the habit of smoking has been extensively documented, the associations between BMI and carotenoid scores remain controversial [27, 28]. Our results are in line with those reported by the majority of studies on adults [29–31], in which a negative association between skin carotenoid levels and BMI was observed. This relationship, which might be due to the distribution of the carotenoids in the adipose tissue, offers further insight into the interplay between skin carotenoid levels and body composition. Although discrepant data were reported on the correlation between sex and carotenoids [27], in line with the results obtained in previous works [14, 32], we also observed that the carotenoid score is higher in men than women, sustaining the importance of the sexual dimorphism. Interestingly, this is the first study, to the best of our knowledge, investigating the correlation between the skin carotenoid levels and FV supply source. We found that participants who stocked up on FV from gardens had significantly higher carotenoid scores compared to those who obtained FV from markets. This result might depend on differences in carotenoid content of FV sold in gardens and markets such as freshness, cultivation methods, and post-harvest processing, highlighting the importance of the food quality that could drive towards correct and healthy food choices.

Another important lifestyle factor influencing the development of NCDs is represented by healthy diet. Among the recommended dietary pattern, MD has been considered the healthiest one, worldwide. The young adults of our sample population exhibited a medium adherence to the MD pattern, which was positively correlated with carotenoid score in both univariate and multiple regression analysis. Data related to the average adherence to the MD are in line with our previous observations in subjects living in the same geographical region [32–35], highlighting the importance to encourage nutritional education program to improve the lifestyle toward an optimal adherence to the MD model. Of note, the MD is a plant-based diet in which the healthy dietary pattern is integrated with healthy lifestyles. Overall, these multifaceted aspects of the MD guarantee a better quality of life characterized by a reduced risk of developing several NCDs and lower cause-specific mortalities [36–40].

Indeed, adequate rest, regular physical activity and social interactions, which are part of the MD, are important lifestyle factors, providing mental and physical health benefits. Our sample population showed a medium adherence to the MD lifestyle, assessed by MEDAS. This result is not surprising since it has been well established the tendency to adhere to unhealthy lifestyles among collegial students [4, 5], but it highlights the need to encourage the young population to follow healthier lifestyle habits. Interestingly, in univariate analysis, the adherence to the MD was positively associated with the skin carotenoid content, confirming that carotenoid score might be used as an objective biomarker to evaluate the adherence to the MD pattern. Overall, when we consider as variables FV supply source and FV consumption or the adherence to the MD pattern, skin carotenoid levels remain positively associated with age, male gender, healthy dietary behaviors and negatively associated with BMI and smoking status. Other potential confounders, including the socioeconomic status and the genetic background, were not included in the analysis since the participants were recruited exclusively from Italian students attending the University of Calabria, thereby ensuring the homogeneity of our sample population. Furthermore, the Veggie Meter® identifies and corrects for individual melanin concentration by using an algorithmic deconvolution adjustment, which allows to minimize the interference from skin pigmentation [15].

A limitation of our study is its cross-sectional design, which does not permit for the evaluation of causal relationships. Longitudinal observational and interventional studies are therefore warranted to further investigate the temporal relationship between dietary patterns, lifestyle behaviors, and skin carotenoid status using the Veggie Meter®.

Conclusions

Our findings highlight the importance of measuring skin carotenoids, as a useful health biomarker. A combination of recommended dietary habits with healthy lifestyle behaviors improves skin carotenoid content, which acting as potent natural antioxidants, may prevent the risk of developing NCDs. These results provide crucial insights for designing health education programs aimed at improving lifestyle habits in young populations.

Abbreviations

BMI

Body mass index

CI

Confidence interval

FV

Fruit and vegetable

MD

Mediterranean Diet

MEDAS

Mediterranean Diet Adherence Screener

MEDLIFE

Mediterranean Lifestyle Index

NCDs

Non-communicable diseases

SD

Standard deviation

Author contributions

The MeDiet Working Group: Data collection. Giuseppina Augimeri: study design, writing the manuscript, analyses and interpretation of data; Danilo Lofaro: analyses and interpretation of data. Adele Vivacqua, Ines Barone, Cinzia Giordano, Catia Morelli, Domenico Conforti, Diego Sisci, Stefania Catalano: interpretation of data and reviewing of the manuscript. Daniela Bonofiglio: conception of the idea, study design, interpretation of data, editing and reviewing of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Department of Excellence (Italian Law. 232/2016), the Department of Pharmacy, and the Health and Nutritional Sciences, University of Calabria; PRIN 2022, European Union; NextGeneration EU initiative under the Italian Ministry of University and Research—M4C2-I1.1 (# 2022AA4FTJ, CUP H53D23006420006) to Giordano C; PRIN PNRR 2022-European Union; NextGenerationEU initiative under the Italian Ministry of University and Research as part of the PNRR—M4C2-I1.1 (#P2022YAKJY, CUP H53D23010120001) to I. Barone.

Data availability

The data presented in this study are available in this article.

Declarations

Ethics approval and consent to participate

The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Ethics Committee of the University of Calabria, Italy (approval number: #0735744/2023). Informed consent was obtained from all subjects involved in the study.

Competing interests

The authors declare no conflict of interest.