The age-risk relationship of hematologic malignancies in patients with rheumatoid arthritis: a nationwide retrospective cohort study

The risk of hematologic malignancies in rheumatoid arthritis (RA) patients has been an important clinical concern. The information of age effect on the interval from the diagnosis of RA to that of hematologic malignancies is limited. This study aimed to define the age-risk relationship between hematologic malignancies and RA. A retrospective cohort study was conducted nationwide with 17,472 patients and 87,360 controls from the Taiwan National Health Insurance Database covering 1997-2008. The subsequent development of hematologic malignancy was observed. The age-adjusted standardized incidence ratios (SIRs), incidence per 1000 person-years, follow-up duration for the diagnosis of hematologic malignancies, and cumulative hazard rates of hematologic malignancies between RA and controls were analyzed. Significantly higher incidences of both lymphoid and myeloid malignancies were found in male RA patients compared with RA-free patients (SIR 3.36, 95 % CI = 2.03-5.57, and SIR: 3.69, 95 % CI = 2.46-5.53). A significantly increased overall incidence risk was found in lymphoid malignancies (SIR 3.00, 95 % CI = 2.22-4.05) but not significantly increased in myeloid malignancies (SIR 1.54, 95 % CI = 0.95-2.50) in female RA. The follow-up duration for hematologic malignancies was significantly shorter in RA patients than in RA-free patients in both males and females (70.70 vs. 103.80 months and 67.73 vs. 100.93 months, respectively). Additionally, higher cumulative hazard rates in both lymphoid and myeloid malignancies were found in male RA patients (p < 0.0001). RA patients have a shorter incubation time to hematological malignancies while comparing to the RA-free people, and the risks are variable in gender and different age groups.