Perceived psychosocial job stress and sleep bruxism among male and female workers

Global Prevalence of Sleep Bruxism and Awake Bruxism in Pediatric and Adult Populations: A Systematic Review and Meta-Analysis

Background/Objectives: The purpose of this systematic review was to assess the global prevalence of sleep bruxism and awake bruxism in pediatric and adult populations. Methods: This systematic review was conducted by analyzing studies published from 2003 to 2023. The following keyword combination was utilized: prevalence, epidemiology, population, and bruxism. The PubMed database was analyzed, supplemented by manual searches using the Google search. Additionally, the snowballing procedure method was applied. A double assessment of the quality of publications was carried out to preserve the highest possible quality of evidence (e.g., Joanna Briggs Institute critical appraisal checklist). Analyses were conducted using the R statistical language. Results: The global bruxism (sleep and awake) prevalence is 22.22%. The global sleep bruxism prevalence is 21% and awake prevalence is 23%. The occurrence of sleep bruxism, based on polysomnography, was estimated at 43%. The highest prevalence of sleep bruxism was observed in North America at 31%, followed by South America at 23%, Europe at 21%, and Asia at 19%. The prevalence of awake bruxism was highest in South America at 30%, followed by Asia at 25% and Europe at 18%. Conclusions: One in four individuals may experience awake bruxism. Bruxism is a significant factor among women. It was observed that age is a significant factor for the occurrence of sleep bruxism in women. Among the limitations of the study is the lack of analysis of the prevalence of bruxism in Africa and Australia due to not collecting an adequate sample for analysis. The study was registered in the Open Science Framework (10.17605/OSF.IO/ZE786).

Evaluation of biochemical changes and treatment efficacy in patients with bruxism following botulinum toxin or splint therapy: a randomized clinical trial

OBJECTIVES

This clinical study aims to analyze the levels of cortisol, dehydroepiandrosterone (DHEA), and tumor necrosis factor alpha (TNF-α) in the gingival crevicular fluid (GCF) of persons with bruxism and to compare the efficacy of botulinum toxin (botox) and occlusal splint treatments through biomarkers.

MATERIALS AND METHODS

A total of 40 patients with bruxism were selected according to the clinical examination and anamnesis of which 20 received occlusal splint treatment and 20 botox treatment. GCF samples were taken from the patients before and after treatment. Cortisol, DHEA, and TNF-α levels were measured by enzyme-linked immunosorbent assay test. The change in measurements between time and groups and the time-group interaction were tested by repeated measures ANOVA.

RESULTS

There was a statistically significant difference between the cortisol levels before and after treatment in both groups (p = 0.001). In individuals with bruxism, a statistically significant decrease in cortisol levels was observed after both treatments (p < 0.05), while DHEA levels increased after treatment but were not statistically significant (p > 0.05). There was no statistically significant difference between TNF-α intra-group measurements (p > 0.05).

CONCLUSIONS

Stress and inflammatory biomarkers were found to be associated with bruxism. Cortisol levels decreased in people with bruxism after treatment with both occlusal splint and botox.

CLINICAL RELEVANCE

Both splint and botox treatments were effective for bruxism by reducing the stress levels.

Circadian preference and its relationship with possible sleep and awake bruxism in adults assisted by the public health system

Modern lifestyle and social demands induce changes in sleep routines that may not meet individual circadian preferences (chronotype). Such changes may be associated with the development of unhealthy lifestyles and the emergence of diseases relevant to public health services, such as obesity, hypertension, and diabetes mellitus, as well as sleep bruxism (SB) and awake bruxism (AB). The present study aimed to assess the relationship between the evening, morning or intermediate chronotypes with the report of possible SB and AB in adult individuals assisted by the Family Health Strategy (FHS). The selection of participants was performed through probabilistic cluster analysis. The sample size (n = 384) was calculated to include a representative sample of the 52,628 adults registered in the FHS of a countryside city located in the Southeast Region of Brazil. The Morningness-Eveningness Questionnaire (MEQ) was used to determine the chronotype, and Questionnaire-Based Self-Reported Bruxism was used for identifying possible SB and AB. The following clinical and social-behavioral variables were also evaluated: age, sex, BMI, income, physical activity, schooling, alcohol consumption and smoking, chronic diseases and depression. Two logistic regression models were used: one for SB and one for AB. Possible SB was associated with female sex, lack of physical activity and income above 2 minimum wages. Regarding chronotype, a 19% reduction in the chance of possible SB was observed in morning individuals compared to evening individuals (p = .017). Possible AB was associated with younger individuals, smoking and depression. In conclusion, compared with the evening circadian preference, the morning circadian preference was associated with greater protection against possible SB in an adult population assisted by the FHS.

Association between sleep bruxism and stress symptoms in adults: A systematic review and meta-analysis

To synthesise and critically review the association between sleep bruxism (SB) and stress symptoms in adults. A systematic review was performed. The search was completed using seven primary electronic databases in addition to a grey literature search. Two reviewers blindly selected studies based on pre-defined eligibility criteria. Risk of bias of the included articles was performed using the Joanna Briggs Institute Critical Appraisal Checklist for Analytical Cross-Sectional Studies. RevMan 5.4 was used to perform the meta-analysis. The quality of evidence was evaluated according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE). Ten studies were included for qualitative analysis, of which three were included for quantitative analysis. Three studies were evaluated to have low risk of bias, and seven were assessed with moderate risk of bias. Quality of evidence was classified as very low for all outcomes. Individuals with SB were found to have higher levels of some self-reported stress symptoms as assessed through questionnaires with a mean difference of 4.59 (95% CI 0.26-8.92). Biomarkers like epinephrine, norepinephrine, cortisol, adrenaline, dopamine, noradrenaline and prolidase enzyme levels also showed a positive association with SB. Although some associations were identified between probable SB and self-reported stress symptoms and biomarkers of stress in adults, given that the quality of evidence was found to be very low, caution should be exercised in interpreting these results. These findings suggest that additional and better designed studies are warranted in order to clarify the link between SB and stress.

Estudo transversal do autorrelato de bruxismo e sua associação com estresse e ansiedade

Resumo Introdução O bruxismo é uma condição prevalente e pode ser destrutivo à cavidade bucal, sendo amplamente abordado na Odontologia, especialmente por sua etiologia multifatorial e prevalência controversa. Objetivo Este estudo teve o objetivo de investigar a prevalência do autorrelato de bruxismo entre universitários e correlacionar a parafunção com a ansiedade e o estresse autopercebidos Material e método Utilizaram-se o autorrelato de bruxismo, Inventário de Ansiedade Traço-Estado (IDATE) e Inventário de Sintomas de Estresse de LIPP (LIPP) para avaliar a prevalência de bruxismo, ansiedade e estresse, respectivamente. Setecentos e quatorze estudantes de todos os cursos da universidade foram entrevistados, com idade entre 18 e 45 anos. Análises estatísticas descritivas foram realizadas por cálculos de frequências (absolutas e relativas), bem como medidas de tendência central e dispersão (média e desvio padrão). Quanto às análises estatísticas inferenciais, o teste qui-quadrado ou exato de Fisher foi utilizado na comparação de proporções e o teste t de Student ou ANOVA, como critério para comparar médias, todos com nível de significância de 5%. Resultado A prevalência de bruxismo foi 46,92%; houve diferença significante da proporão do bruxismo com a ansiedade estado (p = 0,00) e traço (p ≤ 0,0001) de personalidade. Conclusão Conclui-se que, apesar de o bruxismo não ter prevalecido entre estudantes, um elevado percentual de estudantes afirmou realizar essa atividade repetitiva e a proporção de bruxistas com ansiedade foi relevante, evidenciando a importância desse fator psicológico na fisiopatologia da parafunção.

Psychosocial Predictors of Bruxism

OBJECTIVES

The study aimed to investigate the psychosocial predictors of bruxism. The association of various psychosocial factors such as alexithymia, emotional processing, state and trait anxiety, and stress with awake bruxism was analysed.

METHODS

The study involved 52 volunteers diagnosed with awake bruxism. The toolkit that was used included the Toronto Alexithymia Scale (TAS-20), the Emotional Processing Scale (EPS), the Cohen Perceived Stress Scale (PSS-10), and the State- and Trait-Anxiety Inventory (STAI), with independent individual psychological diagnoses being made for every patient. The results were statistically analysed using IBM SPSS Statistics 24.

RESULTS

The obtained data clearly show that psychological traits-both permanent dispositions (e.g., state anxiety and alexithymia) and temporary states (e.g., trait anxiety, emotional processing deficits, and psychological stress)-are significant determinants of awake bruxism. The percentage of explained variance indicates the presence of other factors as well.

CONCLUSIONS

Psychosocial factors such as state anxiety and trait anxiety, alexithymia, and perceived stress are as important as somatic causes in the occurrence and maintenance of awake bruxism. The profile of the obtained data suggests the possibility of preventing or minimizing the symptoms of awake bruxism through properly constructed psychoprophylactic interactions.

The Relationship between Sleep Bruxism and Obstructive Sleep Apnea Based on Polysomnographic Findings

Obstructive sleep apnea (OSA) is the most common sleep disorder. Sleep bruxism (SB) is a masticatory muscle activity during sleep that commonly co-occurs with OSA. The presented study aimed to assess this relationship and to identify factors affecting this co-occurrence. Adult patients (n = 110) were evaluated for OSA and SB in a sleep laboratory using polysomnography. The episodes of bruxism and respiratory events were scored according to the standards of the American Academy of Sleep Medicine. The prevalence of OSA and SB was found to be 86.37% and 50%, respectively. The bruxism episode index (BEI) was increased in the group with mild and moderate OSA (apnea–hypopnea index (AHI) <30) compared to that in the group with severe OSA (AHI ≥ 30) (5.50 ± 4.58 vs. 1.62 ± 1.28, p < 0.05). A positive correlation between AHI and BEI was observed in the group with AHI < 30. Regression analysis indicated that higher AHI, male gender, and diabetes were independent predictors for the increased BEI in group with AHI < 30. The relationship between OSA and SB depends on the degree of severity of OSA. OSA is correlated with SB in mild and moderate cases of OSA in the group of patients with increased risk of OSA.

Correlation between Sleep Bruxism, Stress, and Depression-A Polysomnographic Study

Background and objectives: Sleep bruxism is a common phenomenon that can affect approximately 13% of adult population. It is estimated that bruxism can be caused by three types of factors: biological, psychological, and exogenous. There are many scientific reports about the coexistence of bruxism, stress, and psychoemotional disorders. The aim of this study is to evaluate the possible correlation between occurrence of sleep bruxism and perceived stress and depressive symptoms. Material and methods: The material of this study consisted of 77 patients of Clinic of Prosthetic Dentistry operating at the Department of Prosthetic Dentistry, Wroclaw Medical University, Poland in which after using guidelines of the American Academy of Sleep Medicine probable sleep bruxism was fund. Patients then underwent video-polysomnography. Exposure to perceived stress was evaluated with Perceived Stress Scale-10 (PSS-10). Occurrence of depressive symptoms was evaluated with Beck’s Depression Inventory (BDI). Results: The analysis showed lack of statistically significant correlation between Bruxism Episodes Index (BEI) and Perceived Stress Scale–10 and Beck’s Depression Inventory scores (p = 0.64, p = 0.65; respectively), also when comparing study group (bruxers) and control group (non-bruxers) (p = 0.88, p = 0.77; respectively). Conclusion: Intensity of sleep bruxism was not statistically significantly correlated with self-reported perceived stress and depression. This issue requires further research.

Level of work stress and factors associated with bruxism in the military crew of the Peruvian Air Force

BACKGROUND

Military life leads to a great personal sacrifice and labor in the aircrew because they are constantly subjected to innumerable activities which have a great work pressure; therefore, the aim of this study was to determine the level of work stress associated with bruxism in the aircrew of the Peruvian Air Force.

METHODS

This was a cross-sectional study. A total of 204 crew members of the Peruvian Air Force from the Air Group were surveyed, and the stomatological clinical inspection was carried out. Each crew member was evaluated using the validated International Labor Organization-World Health Organization (ILO-WHO) Work Stress Scale, and clinical records were used to diagnose bruxism using the Smith and Knight wear index.

RESULTS

It was found that 93.7% (n = 191) of the crew members were men and 6.3% (n = 13) were women; and the percentage of intermediate-level stress was found to be high in the grade of non-commissioned officers, whereas in the officer grade, the level of stress was low. There was also a statistically significant association between the variables military grade, sex, and age group. The sub-officers presented a higher percentage in the category "with bruxism", while in the rank of officers the category of "non-bruxism" was the most prevalent.

CONCLUSIONS

This study showed a statistically significant association between the variable bruxism and the level of work stress between the military aviators of the Peruvian Air Force (p<0.001).

Bruxismo do sono: estudo de base populacional em pessoas com 18 anos ou mais na cidade de Rio Grande, Rio Grande do Sul

RESUMO: Objetivos: Avaliar a prevalência do bruxismo do sono, bem como seus principais sinais e sintomas, na cidade de Rio Grande, Rio Grande do Sul. Avaliar a associação do bruxismo do sono com sexo, idade, escolaridade e estresse psicológico. Método: O estudo foi do tipo transversal. Uma amostra representativa da população (1.280 pessoas residentes na zona urbana da cidade com idade maior ou igual a 18 anos de idade) foi entrevistada. A avaliação do bruxismo do sono foi realizada por meio de questionário baseado nos critérios diagnósticos da Classificação Internacional de Distúrbios do Sono. Resultados: A prevalência de bruxismo do sono encontrada na população foi de 8,1% (intervalo de confiança de 95% - IC95% - 6,6 - 9,5). Entre os sinais e sintomas da disfunção utilizados para o diagnóstico de bruxismo do sono, o desgaste dentário (70,3%) e a dor nos músculos mastigatórios (44,5%) foram os mais frequentemente relatados pelas pessoas que declararam ranger os dentes durante o sono. Não houve diferença significativa na prevalência de bruxismo do sono entre os sexos. A faixa etária com mais de 40 anos teve maior prevalência de bruxismo do sono. A disfunção foi associada a um maior nível de escolaridade (razão de prevalência - RP = 1,92; IC95% 1,35 - 2,72) e de estresse psicológico (RP = 1,76; IC95% 1,11 - 2,81). Conclusão: O bruxismo do sono tem uma importante prevalência na população em geral, causando diversos danos ao sistema estomatognático. O estresse psicológico é um fator de risco para essa disfunção.

Investigation of neurodegenerative and inflammatory processes in sleep bruxism

Objective: The present study aimed to evaluate the anxiety and optical coherence tomography (OCT) findings in patients with sleep bruxism (SB) and to develop objective measurements to assess the neurodegenerative and inflammatory processes associated with this disease. Methods: A group of 40 SB patients were compared with a control group consisting of 40 healthy individuals (without SB). Anxiety results and the OCT measurements of retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), and choroidal thickness were assessed in both groups. Results: Anxiety values in the bruxism group were significantly higher than those in the control group. The measurements of RNFL, IPL, and GCL in the bruxism group were significantly lower than the control group, whereas the choroidal thickness was significantly higher. Conclusion: According to literature, this is the first study that analyzed the changes in the retinal structures in bruxism, which revealed that SB is a neurodegenerative and inflammatory process.

Comparative Evaluation of Salivary Cortisol Levels in Bruxism Patients Before and After Using Soft Occlusal Splint: An in vivo Study

Introduction

Bruxism is defined as a nonfunctional activity or a parafunctional habit characterized by the unconscious repetitive motion of clenching and/or grinding of the teeth. Soft occlusal splints have been considered as the first-line strategy for treating nocturnal bruxism. Cortisol is a major steroid hormone secreted by fascicular zone of the adrenal cortex, belonging to the glucocorticosteroidal group of hormones. Clinical studies have shown that when humans are placed under stress, the hypothalamic-pituitary-adrenocortical axis is activated, leading to an increase in cortical secretion. However, the effect of splint is questionable by some researchers, and best way to perceive the effect of soft splints in patients with bruxism is by evaluating the stress levels.

Materials and Methods

A total of 20 individuals suffering from bruxism were selected from the Outpatient Department of Prosthodontics and Crown and Bridge, JSS Dental College and Hospital, Mysore. Saliva samples were collected before and after using the occlusal soft splints and subjected to enzyme-linked immunosorbent assay for determining the salivary cortisol levels.

Results

The collected data were subjected to appropriate descriptive statistics, paired sample t-test, and one sample t-test. The paired sample t-test shows that intragroup comparison of the mean cortisol level in the study group shows near significant values, which means there is a decrease in the salivary cortisol levels in patients after using soft occlusal splint, but statistically nonsignificant.

Conclusion

In the present study, it has been found that 70% of individuals after using the soft occlusal splint showed decreased cortisol levels.

Mastication as a Stress-Coping Behavior

Exposure to chronic stress induces various physical and mental effects that may ultimately lead to disease. Stress-related disease has become a global health problem. Mastication (chewing) is an effective behavior for coping with stress, likely due to the alterations chewing causes in the activity of the hypothalamic-pituitary-adrenal axis and autonomic nervous system. Mastication under stressful conditions attenuates stress-induced increases in plasma corticosterone and catecholamines, as well as the expression of stress-related substances, such as neurotrophic factors and nitric oxide. Further, chewing reduces stress-induced changes in central nervous system morphology, especially in the hippocampus and hypothalamus. In rodents, chewing or biting on wooden sticks during exposure to various stressors reduces stress-induced gastric ulcer formation and attenuates spatial cognitive dysfunction, anxiety-like behavior, and bone loss. In humans, some studies demonstrate that chewing gum during exposure to stress decreases plasma and salivary cortisol levels and reduces mental stress, although other studies report no such effect. Here, we discuss the neuronal mechanisms that underline the interactions between masticatory function and stress-coping behaviors in animals and humans.

Workplace psychosocial factors associated with work-related injury absence: a study from a nationally representative sample of Korean workers

BACKGROUND

Little is known about the association between psychosocial factors and injury absence in the workplace.

PURPOSE

This study aims to assess the association of comprehensive workplace psychosocial factors with work-related injury absence among Korean workers.

METHODS

The data (n = 7,856) were derived from the First Korean Working Conditions Survey conducted in 2006 with a representative sample (n = 10,043) of the Korean working population. The survey instrument contained questions about hours of work, physical risk factors, work organization, and the effect of work on health/injury. Work-related injury absence was indicated by a dichotomous variable with at least 1 day absence during the preceding 12 months. Logistic regression models were used to calculate odds ratio and confidence interval (CI). Incremental adjustments for sociodemographic, health behavior, and occupational confounding variables were employed in the models.

RESULTS

The overall 1-year prevalence of work-related injury absence in this study was 1.37 % (95 % CI, 1.11-1.63 %). Those who experienced violence at work (adjusted odds ratio (aOR), 7.05 (95 % CI, 2.69-18.5)), threat of violence at work (aOR, 4.25 (95 % CI, 1.32-13.64)), low job autonomy (aOR, 1.79 (95 % CI, 1.17-2.74)), and high job strain (aOR, 2.38 (95 % CI, 1.29-4.42) had an increased risk of injury absence, compared with their respective counterparts (p < 0.05). Among all job types, skilled workers in Korea were at a near fourfold risk of work absence due to occupational injuries, compared with managers in low-risk jobs.

CONCLUSION

Workplace violence and increased job strain were two key workplace psychosocial factors associated with work-related injury absence.

Influence of psychosocial factors and habitual behavior in temporomandibular disorder-related symptoms in a working population in Japan

Background:

The symptoms of temporomandibular disorders (TMD) are directly influenced by numerous factors, and it is thought that additional factors exert indirect influences. However, the relationships between TMD-related symptoms (TRS) and these contributing factors are largely unknown. Thus, the goal of the present study was to investigate influences on TRS in a working population by determining the prevalence of TRS, analyzing contributing factors, and determining their relative influences on TRS.

Materials and Methods:

The study subjects were 2203 adults who worked for a single company. Subjects completed a questionnaire assessing TRS, psychosocial factors (stress, anxiety, depressed mood, and chronic fatigue), tooth-contacting habit, and sleep bruxism-related morning symptoms, using a 5-point numeric rating scale. Our analysis proceeded in 2 phases. First, all variables of the descriptor were divided into parts by using an exploratory factor analysis. Second, this factorial structure was verified by using a confirmatory factor analysis with structural equation modeling.

Results:

Of 2203 employees, 362 reported experiencing TRS (16.4%). Structural equation modeling generated a final model with a goodness of fit index of 0.991, an adjusted goodness of fit index of 0.984, and a root mean square error of approximately 0.021. These indices indicate a strong structural model. The standardized path coefficients for “habitual behavioral factors and TRS,” “psychosocial factors and habitual behavioral factors,” “psychosocial factors and TRS,” and “gender and habitual behavior factors” were 0.48, 0.38, 0.14, and 0.18, respectively.

Conclusions:

Habitual behavioral factors exert a stronger effect on TRS than do psychosocial factors.

The psychology of tooth wear

AIM

To review the main psychological and mental conditions that are manifested dentally in the form of tooth wear. These conditions include depression, eating disorders, and alcohol and drug use disorders. The paper will also review the comorbidity of these conditions and the relevance of other medical conditions and lifestyle factors, such as gastroesophageal reflux disorder, smoking and diet, in the expression of tooth wear.

CONCLUSION

A holistic, multidisciplinary, healthcare approach is required in management of tooth wear patients with underlying mental health disorders. Dentists and Dental Care Professionals can have an important role in identifying these mental disorders through the observed tooth wear. They can also play a key role in monitoring patients' response and compliance to medical treatment through the monitoring of tooth wear progression and expression.

Organizational factors associated with work-related sleep problems in a nationally representative sample of Korean workers

Purpose

The purpose of this study was to assess the association of organizational factors with work-related sleep problems (WRSP) among Korean workers.

Methods

The data were derived from the First Korean Working Conditions Survey conducted in 2006 with a representative sample of the Korean working population (n = 10,039).

Results

The overall prevalence of WRSP was 5.1  % (95  % confidence interval (CI) 4.7–5.5). Those who experienced sexual harassment at work (adjusted odds ratio (aOR) 3.47: 95 % CI 1.77–6.81), discrimination due to sex (aOR 2.44: 95 % CI 1.36–4.36) or age (aOR 2.22: 95 % CI 1.52–3.23), violence at work (aOR 1.98: 95 % CI 1.06–3.68), threat of violence (aOR 1.96: 95 % CI 1.05–3.66), poor work-life balance (aOR 1.78: 95 % CI 1.44–2.20), low job satisfaction (aOR 1.69: 95 % CI 1.37–2.09), high cognitive (OR 1.64: 95 % CI 1.32–2.03) and emotional (aOR 1.53: 95 % CI 1.22–1.91) demands, job insecurity (aOR 1.32: 95 % CI 1.07–1.63), and high work intensity (aOR 1.55: 95 % CI: 95 % CI 1.25–1.92) had an increased risk of WRSP compared to their respective counterparts (p < 0.01). Low social support was not significantly associated with WRSP (aOR 0.88: 95 % CI 0.67–1.15).

Conclusion

The results revealed that poor psychosocial working conditions may be related to a high prevalence of WRSP among representative Korean workers.

Correlation between stress, stress-coping and current sleep bruxism

BACKGROUND

Stress is discussed as a potential factor in the development of sleep bruxism (SB). The aim of this study was to investigate whether specific stress-factors correlate with SB-activity.

METHODS

Sixty-nine subjects, of which 48 were SB-patients, completed three German questionnaires assessing different stress-parameters and stress-coping-strategies: Short questionnaire for recognition of stress-factors (Kurzer Fragebogen zur Erfassung von Belastungen, KFB), Questionnaire for recuperation and strain (Erholungs-Belastungs-Fragebogen, EBF-24 A/3) and the stress-coping questionnaire (Stressverarbeitungsfragebogen-78, SVF-78). The diagnosis of SB was based on the clinical criteria of the American Academy of Sleep Medicine (AASM). The degree of SB-activity was measured by the Bruxcore-Bruxism-Monitoring-Device (BBMD, Bruxcore, Boston, USA), worn for five consecutive nights and analyzed using a computer-based method. Non-parametric Spearman correlation coefficients, rho, were calculated between the psychometric data and the amount of SB-activity measured by a pixel score of the BBMD.

RESULTS

Significant correlations were found for 'daily problems' (r = 0.461, p < 0.01), 'trouble at work' (r = 0.293), 'fatigue' (r = 0.288), 'physical problems' (r = 0.288) and the coping-strategy 'escape' (r = 0.295) (all p < 0.05).

CONCLUSIONS

Within the limitations of this study it could be shown that subjects with high SB-activity tend to feel more stressed at work and in their daily life, which in turn might influence their physical state. These subjects also seem to deal with stress in a negative way. However, due to the rather low to almost moderate correlation coefficients and the descriptive character of the study, further investigations are necessary to examine a possible causal relationship.