Table 3

 Rates and incidence rate ratios (IRR) of atrial fibrillation in study cohort by thyroid status

Thyroid status
Overt hypothyroidismSubclinical hypothyroidismEuthyroidismSubclinical hyperthyroidismOvert hyperthyroidism
All subjects (n=586 460)
No of events4240216 275435183
Time at risk (1000 PY)9.767.5310034.923.7
Incidence rate (No/1000 PY):
 Crude4.36.05.212.57.7
 Age and sex adjusted 4.45.76.48.49.1
Incidence rate ratio (95% CI)*0.67 (0.50 to 0.92)0.88 (0.79 to 0.97)1.00 (reference)1.30 (1.18 to 1.43)1.41 (1.22 to 1.63)
Attributable risk percent†NANA2330
All women (n=355 505)
No of events273038466319141
Time at risk (1000 PY)7.955.4190026.818.9
Incidence rate (No/1000 PY):
 Crude3.45.54.411.97.4
 Age adjusted 3.65.36.28.18.9
Incidence rate ratio (95% CI)*0.58 (0.40 to 0.85)0.86 (0.77 to 0.97)1.00 (reference)1.35 (1.20 to 1.51)1.44 (1.22 to 1.70)
Attributable risk percent†NANA2631
Women aged <65 years (n=277 856)
No of events33314673322
Time at risk (1000 PY)5.334.9150014.213.7
Crude incidence rate (No/1000 PY)0.60.91.02.31.6
Incidence rate ratio (95% CI)*0.51 (0.16 to 1.57)0.76 (0.54 to 1.07)1.00 (reference)1.89 (1.34 to 2.67)1.60 (1.05 to 2.43)
Attributable risk percent†NANA4738
Women aged ≥65 years (n=77 649)
No of events242706999286119
Time at risk (1000 PY)2.720.4457.212.65.3
Crude incidence rate (No/1000 PY)9.013.215.322.722.5
Incidence rate ratio (95% CI)*0.58 (0.39 to 0.87)0.86 (0.76 to 0.97)1.00 (reference)1.27 (1.13 to 1.43)1.40 (1.17 to 1.68)
Attributable risk percent†NANA2129
All men (n=230 955)
No of events1599780911642
Time at risk (1000 PY)1.611.412007.64.3
Incidence rate (No/1000 PY):
 Crude9.18.66.715.39.8
 Age and sex adjusted 10.810.410.813.714.5
Incidence rate ratio (95% CI)*0.95 (0.57 to 1.58)0.94 (0.77 to 1.14)1.00 (reference)1.20 (0.99 to 1.44)1.32 (0.97 to 1.78)
Attributable risk percent†NANA1724
Men aged <65 (n=182 690)
No of events32725422621
Time at risk (1000 PY)1.17.7883.84.13.1
Crude incidence rate (No/1000 PY)2.73.52.96.36.7
Incidence rate ratio (95% CI)*0.81 (0.26 to 2.50)1.20 (0.81 to 1.75)1.00 (reference)1.73 (1.18 to 2.56)2.34 (1.52 to 3.59)
Attributable risk percent†NANA4257
Men aged ≥65 (n=48 265)
No of events127252679021
Time at risk (1000 PY)0.53.8272.83.51.1
Crude incidence rate (No/1000 PY)22.719.019.325.818.8
Incidence rate ratio (95% CI)*1.03 (0.58 to 1.81)0.88 (0.70 to 1.22)1.00 (ref.)1.14 (0.92 to 1.40)0.93 (0.60 to 1.42)
Attributable risk percent†NANA12NA

PY=person years. NA=not applicable.

*Risk estimates are adjusted for sex, age, calendar year, Charlson comorbidity index, and socioeconomic status.

†Attributable risk percent = (IRR−1)/IRR×100.