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Table 3 Incidence and Cox proportional hazard regression with hazard ratios and 95% confidence intervals of osteoarthritis of knees associated with used N-acetylcysteine drug by gender and age group

From: Increased risk of knee osteoarthritis in patients using oral N-acetylcysteine: a nationwide cohort study

Variable N-acetylcysteine used N-acetylcysteine used vs. non-N-acetylcysteine used
No Yes Crude Adjusted HRb
Event Person years IRa Event Person years IRa HR (95%CI) p-value HR (95%CI) p-value
Total 6406 337,321.5 1.90 1834 69,351.19 2.64 1.39 (1.32–1.46) < 0.001 1.42 (1.35–1.49) < 0.001
Gender
 Female 3766 151,082.4 2.49 1092 33,775.32 3.23 1.30 (1.21–1.39) < 0.001 1.39 (1.30–1.49) < 0.001
 Male 2640 186,239 1.42 742 35,575.87 2.09 1.47 (1.35–1.59) < 0.001 1.43 (1.32–1.55) < 0.001
Age group, year
 25–39 years 18 13,345.57 0.13 18 3375.513 0.53 3.89 (2.02–7.48) < 0.001 3.98 (2.03–7.79) < 0.001
 40–64 years 3516 237,534.4 1.48 1147 50,744.04 2.26 1.53 (1.43–1.64) < 0.001 1.44 (1.35–1.54) < 0.001
 Older than 65 years 2872 86,441.49 3.32 669 15,231.64 4.39 1.31 (1.20–1.43) < 0.001 1.33 (1.22–1.44) < 0.001
  1. Abbreviations: a IR Incidence rates, per 100 person-years, HR Hazard ratio, CI Confidence interval
  2. b represented adjusted hazard ratio: mutually adjusted for N-acetylcysteine used, age, gender and baseline comorbidities (as like Table 2) in Cox proportional hazard regression