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Table 2 Incidence rates (per 100,000 patient-years) of influenza and incidence rate ratios adjusted for baseline characteristics in patient subgroups

From: Rheumatoid arthritis and the incidence of influenza and influenza-related complications: a retrospective cohort study

   Incidence rates (per 100,000 patient-years) of influenza Incidence rate ratios adjusted for baseline characteristics (95% CI)
Parameter Age categories Males Females Total Males Females Total
   RA cases Controls RA cases Controls RA cases Controls    
Influenza 18–29 495.81 336.70 534.54 444.42 522.13 409.48 1.72 (0.50, 5.94) 1.54 (0.70, 3.38) 1.57 (0.81, 3.03)
  30–39 761.26 347.99 633.31 387.97 670.90 375.64 2.07 (0.97, 4.38) 1.54 (0.93, 2.54) 1.65 (1.09, 2.51)
  40–49 521.10 379.23 515.93 498.87 517.57 459.64 1.06 (0.62, 1.82) 0.88 (0.62, 1.24) 0.92 (0.69, 1.24)
  50–59 358.50 245.10 381.06 357.66 373.58 319.45 1.38 (0.83, 2.32) 0.94 (0.68, 1.30) 1.06 (0.80, 1.38)
  60–69 299.32 106.51 366.56 200.68 342.11 165.94 2.44 (1.13, 5.26) 1.75 (1.11, 2.76) 1.94 (1.31, 2.86)
  ≥70 309.20 238.81 314.97 252.78 312.93 247.95 0.97 (0.48, 1.96) 0.97 (0.58, 1.62) 0.98 (0.64, 1.48)
  Overall 393.91 245.31 417.18 337.69 409.33 306.12 1.43 (1.09, 1.88) 1.13 (0.95, 1.35) 1.22 (1.05, 1.41)
Influenza complications a 18–29 70.05 0 0 0 22.45 0
  30–39 57.49 0 71.98 0 67.71 0
  40–49 38.61 32.78 71.96 31.89 61.36 32.18 0.45 (0.06, 3.44) 1.45 (0.43, 4.93) 1.10 (0.39, 3.07)
  50–59 59.28 19.50 55.02 20.01 56.43 19.84 1.39 (0.26, 7.46) 2.06 (0.65, 6.47) 1.83 (0.71, 4.69)
  60–69 59.53 35.44 63.02 13.79 61.76 21.77 1.08 (0.25, 4.70) 3.17 (0.67, 14.97) 2.15 (0.77, 6.0)
  ≥70 180.81 79.38 122.12 50.39 142.86 60.42 1.18 (0.39, 3.63) 1.76 (0.65, 4.74) 1.50 (0.71, 3.14)
  Overall 80.28 34.08 71.95 23.55 74.76 27.15 1.30 (0.64, 2.63) 2.17 (1.22, 3.86) 1.82 (1.16, 2.81)
Influenza – no DMARDs or biologics 18–29 541.94 343.41 609.33 456.87 587.11 419.88 1.72 (0.50, 5.49) 1.54 (0.71, 3.38) 1.57 (0.81, 3.04)
  30–39 804.93 352.17 670.75 377.68 710.76 369.80 2.07 (0.97, 4.38) 1.61 (0.97, 2.68) 1.71 (1.12, 2.61)
  40–49 516.81 383.82 526.27 490.36 523.19 455.34 1.08 (0.63, 1.85) 0.90 (0.63, 1.28) 0.94 (0.70, 1.27)
  50–59 387.17 247.13 399.08 358.47 395.08 320.48 1.38 (0.82, 2.31) 0.95 (0.69, 1.32) 1.06 (0.81, 1.40)
  60–69 354.97 107.65 413.55 203.48 391.99 168.05 2.42 (1.12, 5.25) 1.81 (1.14, 2.86) 1.97 (1.33, 2.91)
  ≥70 304.73 240.80 270.23 238.58 282.70 239.35 0.93 (0.45, 1.92) 0.99 (0.57, 1.70) 0.96 (0.62, 1.49)
  Overall 426.42 247.82 437.87 333.77 433.96 304.30 1.44 (1.09, 1.89) 1.17 (0.98, 1.40) 1.25 (1.07, 1.45)
Influenza complications – no DMARDs or biologics a 18–29 76.49 0 0 0 25.21 0 0
  30–39 60.73 0 77.64 0 72.59 0 0
  40–49 41.40 33.17 79.96 32.39 67.40 32.64 0.46 (0.06, 3.44) 1.45 (0.43, 4.93) 1.10 (0.39, 3.07)
  50–59 65.34 19.66 57.68 20.35 60.25 20.11 1.39 (0.26, 7.46) 1.98 (0.62, 6.27) 1.77 (0.69, 4.56)
  60–69 68.26 35.82 72.71 13.98 71.07 22.04 1.02 (0.23, 4.55) 3.56 (0.76, 16.66) 2.13 (0.76, 6.01)
  ≥70 145.29 80.04 112.16 42.47 124.13 55.49 0.99 (0.30, 3.28) 1.83 (0.62, 5.35) 1.40 (0.63, 3.08)
  Overall 76.64 34.43 74.20 22.41 75.03 26.53 1.23 (0.59, 2.51) 2.23 (1.23, 4.03) 1.76 (1.12, 2.77)
Pneumonia complications b <65 49.38 31.92 90.34 34.93 76.75 33.91 1.00 (0.40, 2.45) 2.20 (1.26, 3.85) 1.78 (1.11, 2.85)
  ≥65 134.89 29.83 141.59 47.02 139.25 41.10 1.66 (0.44, 6.26) 2.12 (0.96, 4.68) 2.01 (1.02, 3.95)
  Overall 76.22 31.33 105.54 38.34 95.66 35.95 1.15 (0.55, 2.41) 2.15 (1.36, 3.38) 1.84 (1.25, 2.70)
Stroke/MI complications c <65 52.46 11.97 32.09 18.48 38.83 16.27 3.03 (0.85, 10.83) 1.27 (0.56, 2.90) 1.72 (0.87, 3.40)
  ≥65 87.68 19.90 101.67 47.03 96.78 37.68 2.11 (0.42, 10.50) 1.55 (0.68, 3.50) 1.68 (0.82, 3.47)
  Overall 63.52 14.24 52.70 26.53 56.34 22.34 2.69 (1.0, 7.28) 1.37 (0.77, 2.44) 1.69 (1.02, 2.75)
  1. Note: aInfluenza complications = pneumonia diagnosis (ICD-9 codes 480.xx–486.xx); stroke or MI (ICD-9 codes 410.xx, 430, 431, 432.x, 433.xx, 434.xx, 435.xx, 436); or neurological disorder (ICD-9 codes 320.xx–359.xx); all on or up to 30 days after an influenza diagnosis; bICD-9 codes 480.xx–486.xx; cICD-9 codes 410.xx, 430, 431, 432.x, 433.xx, 434.xx, 435.xx, 436.