Impact of Beta-Blockade on Exercise Capacity in Subjects with Type 2 Diabetes

Abstract

Background: Beta-blockers are prescribed to subjects with type 2 diabetes with coronary disease to reduce all-cause mortality. However, this medication reduces exercise capacity in non diabetic individuals. The purpose of this study was to evaluate the impact of beta-blockade on exercise capacity in diabetic subjects free of coronary disease.

Methods: Ten sedentary men with type 2 diabetes participated in this study. Subjects were treated with oral hypoglycemic agents and/or diet. Exercise capacity was evaluated using an incremental protocol performed on a cycle ergometer. Subjects were evaluated without (WBB group) and following the use of a beta-blocker (Atenolol 100 mg, id) for 5 consecutive days (BB group).

Results: Per study design, subjects were their own control. The BB situation was characterized by a lower resting heart rate (HR) (54±4 vs 74±12 bpm; P < 0.001) and a trend toward a lower resting systolic blood pressure (SBP) (123±11 vs 131±14 mmHg; P=0.1) compared to the WBB evaluation. Even with comparable peak workload achieved (193±27 vs 200±22 watts), there was a 13 % reduction in relative and absolute values of peak oxygen uptake (25.8±3.4 vs 29.7±4.1 ml·kg-1·min-1; P < 0.05 and 2.5±0.5 vs 2.9±0.6 L·min-1 respectively; P < 0.001), a 35 % reduction in peak HR (110±9 vs 169±14 bpm; P < 0.001) and a 21 % reduction in peak SBP (167±24 vs 211±20 mmHg; P < 0.001) in the BB compared to the WBB situation. Also, the BB situation showed a lower peak minute-ventilation (97±15 vs 120±24 L/min; P < 0.05) compared with WBB.

Conclusion: These results suggest that in subjects with type 2 diabetes free of coronary disease, the use of a beta-blockers impedes cardio-respiratory function at peak exercise beyond compensatory mechanisms leading to a decreased exercise capacity.