Characterization of physical activity and sitting time among patients on hemodialysis using a new physical activity instrument.

Objectives: Physical activity questionnaires usually focus on moderate to vigorous activities and may not accurately capture physical activity or variation in levels of activity among extremely inactive groups like dialysis patients.

Design: Cross-sectional study.

Setting: Three dialysis facilities in the San Francisco Bay Area.

Subjects: Sixty-eight prevalent hemodialysis patients.

Intervention: We administered a new physical activity questionnaire designed to capture activity in the lower end of the range, the Low Physical Activity Questionnaire (LoPAQ).

Main Outcome Measure: Outcome measures were correlation with a validated physical activity questionnaire, the Minnesota Leisure Time Activity (LTA) questionnaire and with self-reported physical function (physical function score of the SF-36) and physical performance (gait speed, chair stand, balance, and short physical performance battery). We also determined whether patients who were frail or reported limitations in activities of daily living were less active on the LoPAQ.

Results: Sixty-eight participants (mean age 59 ± 14 years, 59% men) completed the study. Patients were inactive according to the LoPAQ, with a median (interquartile range) of 517 (204-1190) kcal/week of physical activity. Although activity from the LTA was lower than on the LoPAQ (411 [61-902] kcal/week), the difference was not statistically significant (P = .20), and results from the 2 instruments were strongly correlated (rho = 0.62, P < .001). In addition, higher physical activity measured by the LoPAQ was correlated with better self-reported functioning (rho = 0.64, P < .001), better performance on gait speed (rho = 0.32, P = .02), balance (rho = 0.45, P < .001), and chair rising (rho = -0.32, P = .03) tests and with higher short physical performance battery total score (rho = 0.51, P < .001). Frail patients and patients with activities of daily living limitations were less active than those who were not frail or limited.

Conclusions: The LoPAQ performed similarly to the Minnesota LTA questionnaire in our cohort despite being shorter and easier to administer.