To examine underlying etiologic factors that may explain the racial disparity in non-Hodgkin's lymphoma (NHL) incidence patterns.
Patients and Methods
We assessed immune-related conditions and risk of developing NHL among more than 4 million hospitalized US veterans including 9,496 patients with NHL (7,999 white patients and 1,497 black patients) with up to 26 years of follow-up. We used time-dependent Poisson regression to estimate rate ratios (RRs) and 95% CIs for NHL risk among patients with a history of specific autoimmune diseases, infections, and allergies compared with patients without such history, adjusting for attained age, calendar year, race, number of hospital visits, and time between study entry and exit.
Patients with infectious conditions had an increased risk of developing NHL (RR, 1.2; 95% CI, 1.1 to 1.2), particularly for gastrohepatic, genital, and systemic infectious conditions. Patients with autoimmune disease were generally more likely to develop NHL than patients without autoimmune disease, especially for conditions that typically present with detectable autoantibodies with systemic involvement (RR, 2.0; 95% CI, 1.8 to 2.2). Allergies were also associated with increased risk (RR, 1.4; 95% CI, 1.3 to 1.5). Although the risk of NHL was lower for blacks than whites (RR, 0.87; 95% CI, 0.82 to 0.92), blacks had a slightly higher risk of NHL associated with infections than whites (likelihood ratio test, P = .002) and a tendency toward higher risk associated with allergies (likelihood ratio test, P = .05). Risks associated with autoimmune conditions were similar by race (likelihood ratio test, P = .5).
The observed difference in NHL risk by race supports a role for race-related differences in genes regulating immune/inflammatory response.