Randomized double-blind placebo-controlled crossover study of caffeine in patients with intermittent claudication

Abstract

Abstract Background Intermittent claudication is a disabling symptom of peripheral arterial disease for which few medical treatments are available. This study investigated the effect of caffeine on physical capacity in patients with intermittent claudication. Methods This randomized double-blind placebo-controlled crossover study included 88 patients recruited by surgeons from outpatient clinics. The participants abstained from caffeine for 48 h before each test and then received either a placebo or oral caffeine (6 mg/kg). After 75 min, pain-free and maximal walking distance on a treadmill, perceived pain, reaction times, postural stability, maximal isometric knee extension strength, submaximal knee extension endurance and cognitive function were measured. The analysis was by intention to treat. Results Caffeine increased the pain-free walking distance by 20·0 (95 per cent confidence interval 3·7 to 38·8) per cent (P = 0·014), maximal walking distance by 26·6 (12·1 to 43·0) per cent (P < 0·001), muscle strength by 9·8 (3·0 to 17·0) per cent (P = 0·005) and endurance by 21·4 (1·2 to 45·7) per cent (P = 0·004). However, postural stability was reduced significantly, by 22·1 (11·7 to 33·4) per cent with eyes open (P < 0·001) and by 21·8 (7·6 to 37·8) per cent with eyes closed (P = 0·002). Neither reaction time nor cognition was affected. Conclusion In patients with moderate intermittent claudication, caffeine increased walking distance, maximal strength and endurance, but affected balance adversely. Registration number: NCT00388128 (http://www.clinicaltrials.gov).