WHAT
This large cohort study evaluated the incidence and risk factors for active tuberculosis (TB) among elderly individuals aged ≥65 years in Zhenjiang City, Jiangsu Province, China. A total of 39,122 older adults were included after excluding 10 individuals with existing TB at baseline. Participants underwent annual free public health screening in 2016, which included demographic surveys, lifestyle assessment, laboratory testing, and clinical examinations.
At baseline, 46.1% of participants were male. Nutritional status showed that 3.9% were underweight, 47.6% normal weight, 37.5% overweight, and 10.9% obese. Smoking was reported in 16.2% of participants, with 7.2% former smokers. Alcohol consumption was reported by 15.9%, and 12.2% had diabetes. Approximately one-fifth reported regular exercise, while 0.9% had symptoms suggestive of TB. Notably, 65.2% of participants had abnormal findings during physical examinations.
After more than seven years of follow-up, 246 individuals developed active TB, corresponding to an incidence rate of 92.21 per 100,000 person-years (95% CI 81.2–104.3). Among these cases, 51.2% were bacteriologically confirmed, and 4.1% were diagnosed with tuberculous pleurisy. The incidence was substantially higher among males (140.2 per 100,000 person-years) compared with females (51.4 per 100,000 person-years).
Nutritional status was strongly associated with TB risk. Underweight individuals had the highest incidence rate (390.3 per 100,000 person-years), whereas obese individuals had the lowest incidence (34.1 per 100,000 person-years). Former smokers also showed markedly higher TB risk, with incidence rates nearly four times higher than never-smokers and three times higher than current smokers.
In multivariable analysis, increasing age remained associated with higher TB risk (adjusted hazard ratio [AHR] 1.03 per year increase, 95% CI 1.01–1.04). Male sex was associated with significantly increased risk (HR 2.73, 95% CI 2.08–3.58). Compared with obese individuals, those with normal BMI had nearly three times higher TB risk (AHR 2.87, 95% CI 1.51–5.46), and underweight individuals had nearly ten times higher risk (AHR 9.89, 95% CI 4.92–19.85). Former smoking was also associated with increased risk (AHR 1.35, 95% CI 1.12–1.64).
Population attributable fraction (PAF) analysis showed that normal BMI contributed the largest proportion of TB risk (47.1%), followed by male sex (43.0%), underweight BMI (25.7%), and smoking cessation (1.6%). These findings suggest that demographic and nutritional factors play a major role in TB risk among older adults.
HOW
This study used a population-based cohort design based on annual public health screening services provided to elderly individuals aged ≥65 years in Zhenjiang City, China, between January and December 2016. These government-sponsored screenings included demographic surveys, lifestyle questionnaires, clinical examinations, and laboratory testing such as blood glucose, lipid profiles, electrocardiogram, complete blood count, urinalysis, and abdominal ultrasound.
Individuals with symptoms suggestive of TB—including persistent cough, hemoptysis, unexplained weight loss, fever, night sweats, chest pain, or lymph node swelling—underwent additional chest X-ray screening. Active TB cases were identified by linking participants to the Tuberculosis Management Information System using identification numbers. Diagnoses were verified through consultation with physicians at designated TB hospitals.
TB cases were classified as bacteriologically confirmed or clinically diagnosed. Bacteriological diagnosis included sputum smear, culture, GeneXpert testing, or pathological confirmation. Clinical diagnosis required negative bacteriological testing but compatible chest X-ray findings and clinical symptoms or supportive immunologic tests such as tuberculin skin test or interferon-gamma release assay.
Baseline variables included BMI, smoking status, alcohol use, diabetes, physical activity, and abnormal physical examination findings. BMI was categorized as underweight, normal, overweight, and obese according to Chinese guidelines. Diabetes control was classified using fasting plasma glucose levels, and abnormal physical examination referred to any abnormal clinical findings during screening.
Participants were followed for more than seven years to identify incident TB cases. Incidence rates were calculated per 100,000 person-years. Risk factors were evaluated using both univariate and multivariable Cox proportional hazards models. Population attributable fractions were calculated to estimate the contribution of key risk factors to TB incidence.
Source: Jiang, H., Chen, X., Lv, J., Dai, B., Liu, Q., Ding, X., Pan, J., Ding, H., Lu, W., Zhu, L. and Lu, P., 2024. Prospective cohort study on tuberculosis incidence and risk factors in the elderly population of eastern China. Heliyon, 10(3).
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