Abstract
IMPORTANCE: Research suggests that increased mitochondrial DNA copy number (mtDNAcn) is associated with increased risk of non-Hodgkin lymphoma (NHL); however, no studies to date have evaluated whether the mitochondrial DNA fraction with breaks (mtDNAfb) is associated with risk of NHL. OBJECTIVE: To evaluate the association of mtDNAfb with NHL risk. DESIGN, SETTING, AND PARTICIPANTS: This nested case-control study, which used prospectively collected samples as part of baseline enrollment (from 1985 through 1988) of 29 133 men who smoked for the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study conducted in southwest Finland, included 107 incident NHL cases and 107 controls (matched on date of birth ±5 years). Analyses were conducted from January to September 2022. EXPOSURE: High-throughput real-time polymerase chain reaction assays quantifying mtDNAfb. MAIN OUTCOMES AND MEASURES: Incident NHL cases were identified in the ATBC Study through April 30, 2002, using the Finnish Cancer Registry and the Register of Causes of Death. The mtDNAfb was quantified and categorized based on the median, tertile, and quartile distributions among controls. Odds ratios (ORs) and 95% CIs were estimated using conditional logistic regression models to assess the associations between categorized mtDNAfb and future risk of NHL, controlling for age, body mass index, number of cigarettes smoked per day, number of pack-years, and mtDNAcn. RESULTS: A total of 29 133 men (median [IQR] age, 57.2 [52.6-62.5] years) participated in ATBC Study. Higher mtDNAfb was associated with an increased risk of NHL (median OR, 2.89; 95% CI, 1.40-5.93) in a dose-dependent manner (quartile 2 vs 1 OR, 1.24; 95% CI, 0.43-3.40; quartile 3 vs 1 OR, 3.58; 95% CI, 1.39-9.24; quartile 4 vs 1 OR, 3.42; 95% CI, 1.30- 8.99; P = .004 for trend). CONCLUSIONS AND RELEVANCE: This study's findings suggest that increased mtDNAfb is associated with an increased future risk of NHL. Additional studies are needed to confirm these findings, particularly among women and nonsmokers.