Overweight and Obesity as Predictors of Work-Related Upper Extremity Disability among Dentists in Arak, Iran: A Cross-Sectional Study

Technical Summary: Overweight and Obesity as Predictors of Work-Related Upper Extremity Disability among Dentists in Arak, Iran

Problem Statement
Musculoskeletal disorders (MSDs) represent a pervasive occupational health challenge for dental professionals, driven by prolonged static postures, repetitive fine motor movements, and the use of vibrating instruments. While the prevalence of MSDs in dentistry is well-documented, with rates often exceeding 50–70% in various studies, the specific role of Body Mass Index (BMI) as an independent, modifiable risk factor for upper extremity disability remains underexplored. Existing literature has largely focused on the association between high BMI and low back pain, leaving a gap in understanding how obesity impacts non-weight-bearing regions such as the shoulders, arms, and hands in the context of dental practice. This study addresses the need to investigate the association between BMI categories and work-related upper extremity disability among dentists in Arak, Iran, to inform targeted preventive strategies.

Methodology
The study employed a descriptive-analytical cross-sectional design conducted over a 12-month period (2025–2026) in Arak city, Iran.

• Participants: A convenience sample of 276 dentists actively practicing in the region was recruited. Inclusion criteria required a valid dental license and active practice in 2025; exclusion criteria included recent trauma or systemic rheumatic diseases unrelated to dental practice.
• Data Collection:
  • Demographics and Occupation: A researcher-developed questionnaire captured age, gender, work experience, working hours, and physical activity.
  • Anthropometry: Height and weight were measured directly to calculate BMI, categorized according to WHO standards (Underweight, Normal, Overweight, Obese).
  • Musculoskeletal Symptoms: The Extended Nordic Musculoskeletal Questionnaire (NMQ-E) was used to assess the prevalence of symptoms in nine anatomical regions over the past 12 months and 7 days.
  • Disability Assessment: The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, a validated Persian instrument with high internal consistency (Cronbach's alpha = 0.96), was used to quantify functional limitations and symptom severity.
• Statistical Analysis: Data were analyzed using SPSS v26.0. Associations between categorical variables and disability severity were tested using Chi-square and Fisher's exact tests. Mean DASH scores were compared using t-tests, ANOVA, or non-parametric equivalents. Binary logistic regression was utilized to determine independent predictors of upper extremity disability (defined as DASH score > 20), adjusting for gender, age, and work experience.

Key Results

• Demographics and Prevalence: The sample consisted of 51.4% males and 48.6% females. The prevalence of overweight was 36.6%, and obesity was 19.2%.
• Symptom Distribution: The shoulder was the most frequently affected site (58.7% over 12 months), followed by the wrist/hand (53.6%) and neck (47.8%). Functional limitations were most commonly attributed to neck complaints (22.4%).
• Disability Severity: Based on DASH scores, 34.8% of participants had mild disability, 44.9% moderate, and 20.3% severe disability.
• BMI Association: A clear dose-response relationship was observed between BMI and upper extremity disability.
  • Overweight: Dentists with a BMI of 25.0–29.9 kg/m² had 1.84 times higher odds of disability compared to normal-weight dentists (Adjusted OR = 1.84, 95% CI: 1.02–3.32, p = 0.04).
  • Obesity: Dentists with a BMI ≥ 30.0 kg/m² had nearly three times higher odds of disability (Adjusted OR = 2.98, 95% CI: 1.42–6.25, p = 0.004).
• Other Factors: No statistically significant associations were found between upper extremity disability and gender, age, or years of work experience after adjustment.

Key Contributions
This study provides empirical evidence that elevated BMI is an independent predictor of upper extremity disability in dentists, distinct from traditional demographic and occupational factors. By utilizing the DASH questionnaire, the research quantifies the functional impact of weight status, moving beyond simple symptom prevalence. The identification of a dose-response relationship strengthens the argument that excess body weight exacerbates musculoskeletal strain in the upper limbs, likely through combined biomechanical loading and systemic inflammatory pathways.

Significance and Claims
The authors claim that these findings highlight the necessity of integrating weight management into occupational health strategies for dental professionals. The study posits that because BMI is a modifiable risk factor, interventions targeting weight reduction, alongside ergonomic improvements, could significantly reduce the burden of MSDs. The authors suggest that dental training curricula and continuing professional development should address the musculoskeletal risks associated with excess body weight. Furthermore, they advocate for routine occupational health evaluations that include BMI screening, with personalized ergonomic assessments for overweight and obese practitioners. The paper concludes that addressing modifiable lifestyle factors is crucial for promoting long-term musculoskeletal health in the dental workforce, while acknowledging that future longitudinal and interventional studies are needed to confirm causal mechanisms and the efficacy of weight-loss interventions.