A multicenter study of sleep-wake rhythm disorders: therapeutic effects of vitamin B12, bright light therapy, chronotherapy and hypnotics

OBJECTIVES: To compare the single and joint effect of 1-year diet and exercise intervention on carbohydrate metabolism and associated coronary risk variables. DESIGN: Unmasked, randomized, 2 x 2 factorial intervention trial with 1-year duration for each participant. SETTING: The participants were recruited from a screening examination of 40-year-old persons in Oslo, Norway. SUBJECTS: Two hundred and nineteen sedentary men and women, with diastolic blood pressure 86-99 mmHg, HDL cholesterol < 1.20 mmol L-1, triglycerides > 1.4 mmol L-1, total cholesterol 5.20-7.74 mmol L-1 and BMI > 24. Participants were randomly allocated to control (n = 43), diet (n = 55), exercise (n = 54) and diet+exercise (n = 67). INTERVENTIONS: Exercise: supervised endurance exercise three times a week. Diet: reduce weight, increase the intake of fish and reduce total fat intake. MAIN OUTCOME MEASURES: One-year changes in insulin and glucose before and after a standardized glucose load. RESULTS: As compared with controls fasting insulin in pmol L-1 decreased significantly in the combined diet and exercise group (3.9 +/- 6.2 versus -22.6 +/- 4.7 respectively, P = 0.003). Insulin in pmol L-1 after glucose load decreased significantly in all intervention groups compared to controls (diet: -82.2 +/- 49.9 P = 0.02; exercise: -92.4 +/- 60.1 P = 0.03; diet + exercise: -179.6 +/- 46.1 P = 0.0004). Fasting glucose in mmol L-1 decreased significantly in the diet alone group (0.21 +/- 0.07 P = 0.006) and in the diet+exercise group (-0.26 +/- 0.08 P = 0.005). In a subgroup analysis of the good responders, the observed changes with respect to total cholesterol (-0.76 mmol L-1), HDL cholesterol (0.16 mmol L-1), triglycerides (-0.72 mmol L-1), systolic and diastolic blood pressure (-8.5/ -6.8 mmHg) were all statistically significant compared to the control with P < 0.001). CONCLUSIONS: Exercise and diet intervention and in particular the combination of the two, were effective in improving carbohydrate metabolism. Associated risk factors were also affected in a beneficial direction.