home-based walking study in older adults with type 2 diabetes

Conditions: Cardiovascular; Diabetes; Orthostatic Hypotension; Type 2 Diabetes

Summary: older persons with diabetes have a harder time maintaining blood pressure when standing up. when blood pressure drops when standing up, fainting may occur. this study will see how regular exercise can improve the ability of the body to keep blood pressure up when standing. we want to see how this improvement varies with a home-based walking program.

detailed summary 1. purpose: older adults with diabetes faint frequently, due to an impairment in the cardiovascular control mechanisms (arterial baroreceptor function, autonomic nervous system function and cerebral autoregulation) that prevent syncope. the purpose of this study is to examine the ability of a home based walking program to reverse these impairments. 2. hypotheses: a) a home-based walking program will improve the compensatory cardiovascular responses that prevent syncope in older adults with type 2 diabetes. a moderate, regular exercise program will: * increase arterial baroreflex sensitivity * increase heart rate variability (marker of autonomic nervous system function) * decrease cerebrovascular resistance * improve cerebral autoregulation during upright tilt. b) there will be relationship between the improvement in compensatory cardiovascular responses and regular exercise. c) design of more practicable training prescriptions than that used in a research setting.

Eligibility criteria:
inclusion criteria: * type 2 diabetes for at least 5 years treated with diet alone or oral agents * nonsmoker for at least 5 years * subjects must be sedentary (as defined by no strength training and less than 30 minutes brisk walking/moderate exercise per week and no vigorous exercise in the preceding 6 months) * all subjects will have a fasting glucose of \<12 mm and a hemoglobin a1c \< 8.5% * orthostatic hypotension defined as a decrease in systolic blood pressure of at least 20 mm hg or diastolic blood pressure of at least 10 mm hg within 3 minutes of assuming an upright posture on the initial screening visit as per current american academy of neurology guidelines. exclusion criteria: * abnormalities on complete blood count, electrolytes or creatinine, on resting ecg, treadmill exercise stress test * significant pulmonary, exercise-limiting orthopedic or neurological impairment * evidence of valvular disease, exercise-induced syncope, angina, arrhythmias or peripheral vascular disease * poor blood pressure control as defined as systolic blood pressure greater than or equal to 160 mm hg or diastolic blood pressure greater than or equal to 90 mm hg * total cholesterol/hdl cholesterol greater than or equal to 5.0 or ldl cholesterol greater than or equal to 4.21 mmol/l * peripheral neuropathy severe enough to cause discomfort (for safety reasons) * overt diabetic nephropathy excluding subjects with a urine albumin to creatinine ratio of greater than 2.0 in men or 2.8 in women * diabetic retinopathy

Keywords: aging type 2 diabetes exercise walking glucose metabolism arterial baroreceptors heart rate variability cerebral autoregulation tilt table study transcranial doppler autonomic nervous system