The Nature of the Relationship Between Smoking and Ulnar Neuropathy at the Elbow

Objective: To confirm that smoking increases the risk for ulnar neuropathy at the elbow and to investigate potential mechanisms for that increased risk. Design: Prospective case-control study featuring the recruitment of 100 subjects with upper-limb neurologic symptoms: 50 meeting (cases) and not meeting (controls) electrodiagnostic criteria for ulnar neuropathy at the elbow. Known risk factors for ulnar neuropathy at the elbow, preferred smoking hand, and upper-limb joint angles during preferred smoking posture were recorded. Results: Subjects with ulnar neuropathy at the elbow reported increased smoking when compared with the control group, but there was no agreement between ulnar neuropathy at the elbow side and preferred smoking hand or group differences in joint angles during preferred smoking posture. Ulnar neuropathy at the elbow occurred more frequently on the left regardless of hand dominance (P = 0.007). Independent risk factors included age, male sex, and smoking (in pack-years), demonstrating odds ratios (95% confidence intervals) of 1.054 (1.015-1.095), 4.41 (1.75-11.16), and 1.035 (1.001-1.070), respectively. Smoking also correlated negatively with above-elbow ulnar compound muscle action potential, across-elbow conduction velocity, and conduction block. Conclusions: Smoking is associated with increased risk for ulnar neuropathy at the elbow, and the dose-response effect between smoking and electrophysiologic ulnar measures associated with ulnar neuropathy at the elbow severity increases the likelihood that the relationship is one of cause and effect. However, the data do not suggest that a mechanical explanation related to repetitive elbow flexion is likely.