Urinary Function and Multimorbidity Risks: A Longitudinal Study in Beijing Community-Dwelling Elderly

Primary outcomes

1. Annual Incidence of Age-Related Multimorbidity Associated with Urinary Function

   Time frame: Baseline (at enrollment), 12 months after enrollment (1st annual assessment), 24 months after enrollment (2nd annual assessment), through study completion (average follow-up duration: 3 years)

   This outcome measures the incidence of newly developed chronic multimorbidities closely linked to age-related urinary function changes, including metabolic syndrome, cardiovascular diseases, diabetes mellitus, and Alzheimer's disease. Diagnosis is confirmed by clinical diagnostic criteria (e.g., diabetes mellitus defined as fasting blood glucose ≥7.0 mmol/L; hypertension, a subtype of cardiovascular disease, defined as blood pressure ≥140/90 mmHg) combined with medical record review. It reflects the initial association between urinary function and systemic multimorbidity during the aging process. The unit of measurement is "incidence rate (%)".

2. Annual Progression Rate of Age-Related Multimorbidity Associated with Urinary Function

   Time frame: Baseline (at enrollment), 12 months after enrollment (1st annual assessment), 24 months after enrollment (2nd annual assessment), through study completion (average follow-up duration: 3 years)

   This outcome measures the proportion of participants with pre-existing multimorbidities (as specified above) who experience disease deterioration during follow-up. Progression is confirmed by clinical examinations and medical record review, including escalation of disease severity (e.g., progression from grade 1 to grade 2 hypertension) or occurrence of complications (e.g., diabetic nephropathy). It reflects the interactive worsening trend between urinary function and multimorbidity with aging. The unit of measurement is "progression rate (%)".

3. Annual Change in International Prostate Symptom Score (IPSS)

   Time frame: Baseline (at enrollment), 12 months after enrollment (1st annual follow-up), 24 months after enrollment (2nd annual follow-up), through study completion (average follow-up duration: 3 years)

   This outcome assesses the annual change in the severity of lower urinary tract symptoms (LUTS) using the standardized IPSS scale (range: 0-35 points). A higher score indicates more severe symptoms such as frequent urination, urgent urination, and dysuria. Participants complete the questionnaire under the guidance of trained healthcare professionals, and data are directly extracted from the scale results. It is a key indicator reflecting core urinary function symptoms. The unit of measurement is "change in score (points)".

4. Annual Change in Maximum Urinary Flow Rate (Qmax)

   Time frame: Baseline (at enrollment), 12 months after enrollment (1st annual follow-up), 24 months after enrollment (2nd annual follow-up), through study completion (average follow-up duration: 3 years)

   This outcome measures the annual change in the maximum speed of urination, which directly reflects bladder contractile function and urinary tract patency. Qmax is measured using a uroflowmeter, with participants required to empty their bladders completely during the test; the device automatically records the maximum flow rate. The unit of measurement is "change in value (mL/s)".

5. Annual Change in Post-Void Residual Urine Volume

   Time frame: Baseline (at enrollment), 12 months after enrollment (1st annual follow-up), 24 months after enrollment (2nd annual follow-up), through study completion (average follow-up duration: 3 years)

   This outcome assesses the annual change in the volume of urine remaining in the bladder after voiding, which reflects bladder emptying function. The measurement is performed by professional physicians using ultrasound, and results are reported in milliliters (mL). A volume >50 mL indicates bladder emptying dysfunction. The unit of measurement is "change in volume (mL)".