Associations between spirometric measures and exercise capacity in type 2 diabetes

BACKGROUND

Physical exercise aids glycemic control and the prevention of diabetes-related complications. However, exercise beyond an individual's pulmonary functional capacity may be detrimental. To date, little is known about the relationship between pulmonary function and exercise capacity in people with type 2 diabetes (T2D). We investigated the relationship between pulmonary function and exercise capacity in T2D.

METHODS

Spirometry and 6-min walk test (6MWT) were conducted for 263 systematically sampled adults with T2D without primary heart/lung disease. The primary measure of exercise capacity was the 6-min walk distance (6MWD); impaired exercise capacity was defined as 6MWD<400 m. Logistic regression analyses were used to assess the associations between spirometric measures and exercise capacity with adjustments for age, sex, height, body mass index, diabetes duration, glycated hemoglobin concentration, smoking, suboptimum blood pressure control, and total cholesterol concentration.

RESULTS

Compared with individuals with normal spirometry, those with pulmonary restriction/obstruction had significantly lower 6MWD (404.67 m vs. 451.70),p < 0.001). The proportion of individuals with impaired exercise capacity was higher in individuals with impaired pulmonary function compared with those with normal pulmonary function (39.8% vs. 20.7%,p = 0.001). In the unadjusted models, decreasing Z-score FEV1 [odds ratio 1.40, 95% confidence interval (1.07-1.83),p = 0.013] and Z-score FVC [1.37 (1.06-1.76),0.016], but not Z-score FEV1/FVC ratio [1.00 (0.78-1.27),0.972] were significantly associated with impaired exercise capacity. In the fully adjusted model, the strength of association remained statistically significant for Z-score FEV1 [1.60 (1.06-2.41),0.025] but not Z-score FVC [1.48 (0.98-2.23),0.065].

CONCLUSIONS

Our study shows inverse associations between FEV1 and impaired exercise capacity in T2D, Future research could characterize optimal exercise levels based on a patient's FEV1.

Factors associated with lack of improvement in submaximal exercise capacity of patients with heart failure

AIMS

Improvement in exercise capacity is the primary goal of physical activity programmes for patients with heart failure (HF). Although activity programmes are effective for some patients, others do not benefit. Identifying factors related to a lack of improvement in submaximal exercise capacity may help us interpret findings and design new interventions. The aim of this study is to identify factors contributing to a lack of improvement in submaximal exercise capacity 3 months after physical activity advice or an exergame intervention in patients with HF. Additionally, we aimed to assess differences in lack of improvement in submaximal exercise capacity of patients whose baseline exercise capacity predicted a worse compared with better prognosis of HF.

METHODS AND RESULTS

This secondary analysis of the HF-Wii study analysed baseline and 3 month data of the 6 min walk test (6MWT) from 480 patients (mean age 67 years, 72% male). Data were analysed separately in patients with a pre-defined 6 min walking distance at baseline of <300 m (n = 79) and ≥300 m (n = 401). Among patients with a baseline 6MWT of ≥300 m, 18% had deteriorated submaximal exercise capacity. In the multiple logistic regression analysis, lower baseline levels of self-reported physical activity [odds ratio (OR) = 0.77, 95% confidence interval (CI) = 0.60-0.97], lower baseline levels of cognitive function (OR = 0.87, 95%CI = 0.79-0.96) were significantly associated with lack of improvement in exercise capacity at 3 months. Not randomized to exergaming (OR = 0.63, 95%CI = 0.37-1.09) was likely (P = 0.097) to be associated with lack of improvement in exercise capacity at 3 months. Among the 79 patients with baseline 6MWT of <300 m, 41% (n = 32) did not improve 6MWT distance at 3 months. Independent predictors for the lack of improvement for 6MWT were New York Heart Association class III/IV (OR = 4.68, 95%CI = 1.08-20.35), higher levels of serum creatinine (OR = 1.02, 95%CI = 1.003-1.03), lower cognitive function (OR = 0.86, 95%CI = 0.75-0.99), and fewer anxiety symptoms (OR = 0.84, 95%CI = 0.72-0.98).

CONCLUSIONS

Lower self-reported physical activity and cognitive impairment predict lack of improvement in submaximal exercise capacity in HF patients. Patients who have a worse prognosis (score <300 m at the 6MWT) are often frail and gain less in exercise capacity. These patients may need a more comprehensive approach to have an effect on exercise capacity, including an individually tailored exercise programme with aerobic exercise (if tolerated) and strength exercises.

Iron Status in Chronic Heart Failure: Impact on Symptoms, Functional Class and Submaximal Exercise Capacity

INTRODUCTION AND OBJECTIVES

To evaluate the effect of iron deficiency and anemia on submaximal exercise capacity in patients with chronic heart failure.

METHODS

We undertook a single-center cross-sectional study in a group of stable patients with chronic heart failure. At recruitment, patients provided baseline information and completed a 6-minute walk test to evaluate submaximal exercise capacity and exercise-induced symptoms. At the same time, blood samples were taken for serological evaluation. Iron deficiency was defined as ferritin < 100 ng/mL or transferrin saturation < 20% when ferritin is < 800 ng/mL. Additional markers of iron status were also measured.

RESULTS

A total of 538 heart failure patients were eligible for inclusion, with an average age of 71 years and 33% were in New York Heart Association class III/IV. The mean distance walked in the test was 285 ± 101 meters among those with impaired iron status, vs 322 ± 113 meters (P=.002). Symptoms during the test were more frequent in iron deficiency patients (35% vs 27%; P=.028) and the most common symptom reported was fatigue. Multivariate logistic regression analyses showed that increased levels of soluble transferrin receptor indicating abnormal iron status were independently associated with advanced New York Heart Association class (P < .05). Multivariable analysis using generalized additive models, soluble transferrin receptor and ferritin index, both biomarkers measuring iron status, showed a significant, independent and linear association with submaximal exercise capacity (P=.03 for both). In contrast, hemoglobin levels were not significantly associated with 6-minute walk test distance in the multivariable analysis.

CONCLUSIONS

In patients with chronic heart failure, iron deficiency but not anemia was associated with impaired submaximal exercise capacity and symptomatic functional limitation.