Decreased testosterone levels in middle-aged men are associated with multiple metabolic, functional and psychosocial consequences. Early identification of modifiable factors associated with reduced testosterone levels may facilitate the early identification of men at increased risk of testosterone deficiency and support preventive healthcare strategies. This population-based cross-sectional observational study aims to investigate anthropometric, functional and lifestyle-related factors associated with serum total testosterone levels in middle-aged men. Approximately 600 men aged 35-59 years residing in the Andijan region of Uzbekistan will be recruited. Participants will undergo comprehensive assessment including anthropometric measurements, functional performance tests, standardised questionnaires and laboratory determination of serum total testosterone concentrations. Anthropometric variables will include body mass index, waist circumference, hip circumference, waist-to-hip ratio and waist-to-height ratio. Functional status will be assessed using hand-grip strength, the five-times chair-stand test and the 4-m walk test. Lifestyle-related factors will be assessed using standardised and study-specific questionnaires. Physical activity will be assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF), while dietary habits, sleep characteristics, smoking status, alcohol consumption and psychosocial characteristics will be assessed using a structured study questionnaire. The study aims to identify factors associated with serum total testosterone levels and to develop a predictive model for the early identification of men at increased risk of testosterone deficiency.
Testosterone plays an important role in maintaining male reproductive health, body composition, muscle strength and metabolic homeostasis. Reduced testosterone levels in middle-aged men have been associated with an increased risk of metabolic syndrome, obesity, type 2 diabetes mellitus, cardiovascular diseases, reduced physical performance and impaired quality of life. Despite increasing recognition of testosterone deficiency as an important public health issue, many cases remain unrecognised because of nonspecific clinical manifestations. Previous studies have demonstrated that obesity, physical inactivity, poor sleep quality, unhealthy dietary patterns and other lifestyle-related factors may influence serum testosterone levels. However, the combined associations of anthropometric characteristics, functional status and lifestyle-related factors with serum testosterone levels remain insufficiently investigated, particularly in population-based studies involving middle-aged men. The present study is designed as a population-based cross-sectional observational study aimed at investigating anthropometric, functional and lifestyle-related factors associated with serum total testosterone levels in middle-aged men. Approximately 600 men aged 35-59 years residing in the Andijan region of Uzbekistan will be recruited. Participants will undergo comprehensive assessment including anthropometric measurements, functional performance tests, standardised questionnaires and laboratory determination of serum total testosterone concentrations. Anthropometric variables will include height, body weight, body mass index, waist circumference, hip circumference, waist-to-hip ratio and waist-to-height ratio. Functional performance will be assessed using hand-grip strength, the five-times chair-stand test and the 4-m walk test. Lifestyle-related characteristics will be evaluated using validated questionnaires assessing physical activity, sleep quality, dietary habits, lower urinary tract symptoms, symptoms suggestive of testosterone deficiency and muscle function. Additional information regarding smoking status, alcohol consumption, occupational characteristics, medical history and comorbidities will also be collected. Venous blood samples will be collected between 08:00 and 10:00 hours following an overnight fast. Serum total testosterone concentrations will be measured using standardised laboratory procedures. Statistical analyses will include correlation analyses, multivariable linear and logistic regression models, and receiver operating characteristic (ROC) curve analysis to identify factors associated with serum total testosterone levels and decreased total testosterone levels. Based on the study findings, a multivariable predictive model will be developed for the early identification of men at increased risk of testosterone deficiency. The findings of this study are expected to improve understanding of anthropometric, functional and lifestyle-related factors associated with serum total testosterone levels and to support the development of accessible risk assessment strategies for the early identification of testosterone deficiency in middle-aged men.
Study Type
OBSERVATIONAL
Enrollment
600
Participants undergo standardised anthropometric measurements, functional performance tests, validated questionnaires assessing lifestyle-related factors, lower urinary tract symptoms, symptoms suggestive of testosterone deficiency and muscle function, together with laboratory determination of serum total testosterone concentrations. No therapeutic or preventive intervention is administered.
Andijan State Medical Institute
Andijan, Uzbekistan
RECRUITINGSerum Total Testosterone Level
Serum total testosterone concentration measured in fasting venous blood samples collected between 08:00 and 10:00 hours using a chemiluminescent microparticle immunoassay (CMIA) on the ARCHITECT i1000SR immunoassay analyser (Abbott Laboratories, Abbott Park, IL, USA).
Time frame: At baseline
Correlation between anthropometric characteristics and serum total testosterone levels
Correlations between serum total testosterone concentration (nmol/L) and anthropometric characteristics will be assessed using Pearson or Spearman correlation coefficients, as appropriate. Anthropometric measures include body mass index (BMI, kg/m²), waist circumference (cm), hip circumference (cm), waist-to-hip ratio (dimensionless), and waist-to-height ratio (dimensionless).
Time frame: At baseline
Correlation between functional parameters and serum total testosterone levels
Correlations between serum total testosterone concentration (nmol/L) and functional parameters will be assessed using Pearson or Spearman correlation coefficients, as appropriate. Functional measures include maximal hand-grip strength measured by hand dynamometry (kg), five-times chair-stand test completion time (seconds), and 4-m gait speed (m/s).
Time frame: At baseline
Correlation between physical activity and serum total testosterone levels
Correlation between serum total testosterone concentration (nmol/L) and physical activity level assessed using the International Physical Activity Questionnaire-Short Form (IPAQ-SF), expressed as total physical activity in MET-minutes/week, will be evaluated using Pearson or Spearman correlation coefficients, as appropriate.
Time frame: At baseline
Correlation between sleep duration and serum total testosterone levels
Correlation between serum total testosterone concentration (nmol/L) and self-reported sleep duration (hours per night), assessed using the structured study questionnaire, will be evaluated using Pearson or Spearman correlation coefficients, as appropriate. The correlation will be reported as Pearson's r or Spearman's ρ.
Time frame: At baseline
Association between smoking status and serum total testosterone levels
Serum total testosterone concentration (nmol/L) will be assessed in relation to self-reported smoking status using the structured study questionnaire. Participants will be classified as never smokers, former smokers, or current smokers. Differences in serum total testosterone levels across smoking-status categories will be evaluated using appropriate statistical methods.
Time frame: At baseline
Association between alcohol consumption status and serum total testosterone levels
Serum total testosterone concentration (nmol/L) will be assessed in relation to self-reported alcohol consumption status using the structured study questionnaire. Participants will be classified as non-drinkers, former drinkers, or current drinkers. Differences in serum total testosterone levels across alcohol-consumption categories will be evaluated using appropriate statistical methods.
Time frame: At baseline
Independent factors associated with decreased serum total testosterone levels
Independent anthropometric, functional and lifestyle-related factors associated with decreased serum total testosterone will be evaluated using multivariable logistic regression analysis. Decreased serum total testosterone will be defined according to the prespecified clinically relevant threshold described in the study protocol, and associations will be reported as adjusted odds ratios (ORs) with 95% confidence intervals (CIs). In complementary analyses, serum total testosterone concentration (nmol/L) will be analysed as a continuous outcome using multivariable linear regression, with regression coefficients and 95% CIs reported.
Time frame: At baseline
Development and internal validation of a multivariable predictive model for decreased serum total testosterone
A multivariable predictive model based on anthropometric, functional and lifestyle-related factors will be developed for identification of men with decreased serum total testosterone, defined according to the prespecified clinically relevant threshold. Model discrimination will be quantified using the area under the receiver operating characteristic curve (AUC; range 0-1), with sensitivity and specificity reported as appropriate. Calibration will be assessed using calibration plots and appropriate statistical measures. Internal validation will be performed using bootstrap resampling (1000 samples) to estimate optimism and assess model stability and potential overfitting.
Time frame: At baseline
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