Test-retest study of the six-minute walk test in people with bipolar disorder

BACKGROUND: The multidisciplinary care for bipolar disorder is highly fragmented with limited opportunities for prevention and treatment of medical co-morbidities. We examined the reliability of the 6-minute walk test (6MWT). Secondary aims were to assess minimal detectable changes (MDC(95)), practice effects and the impact of clinical conditions.

SUBJECTS AND METHODS: Two 6MWTs were administered within 3 days to 46 (23♂) inpatients with a DSM-V diagnosis of bipolar disorder. Physical complaints before and after the 6MWT were recorded. Patients completed the Quick Inventory of Depressive Symptomatology Self Report (QIDS-SR) and Hypomania Check List-32.

RESULTS: Patients walked 594.7±121.3 meters and 600.0±122.9 meters at the first and second test. The intraclass correlation coefficient was 0.98 (95% confidence interval 0.97-0.99). The MDC(95) was 37.8 meters for men and 52.9 meters for women. No practice effect was detected. Longer illness duration, higher QIDS-SR scores and the presence of feet or ankle static problems or pain were independently related to shorter 6MWT distance accounting for 59.8% of the variance.

CONCLUSION: The 6MWT is a clinically feasible tool for evaluating the functional exercise capacity in patients with bipolar disorder. Health care professionals should consider depression and physical pain when developing rehabilitation programmes.