Using a single question to assess physical activity in older adults: a reliability and validity study.

Area of Science:

• Gerontology
• Exercise Science
• Psychometrics

Background:

• Single-item physical activity questions offer a rapid assessment of activity levels.
• While detailed questionnaires exist, single-item questions are practical in specific contexts.
• This study evaluated two single-item questions for older adults.

Purpose of the Study:

• To assess the test-retest reliability, convergent validity, and discriminant validity of two single-item physical activity questions.
• To compare an absolute physical activity question with a relative physical activity question in older adults.

Main Methods:

• Data from the Project to Prevent Falls in Veterans was used.
• One question assessed absolute physical activity (seldom, moderately, vigorously active).
• One question assessed relative physical activity (more, about as, less active than peers).
• Test-retest reliability was measured using weighted Kappa statistics (κ).
• Validity was assessed using correlation coefficients (r) with clinical assessments.

Main Results:

• The absolute question showed higher reliability (κ = 0.75) than the relative question (κ = 0.56).
• The relative question demonstrated stronger convergent validity (r = 0.28–0.57) compared to the absolute question (r = 0.10–0.33).
• Discriminant validity was comparable between both questions.

Conclusions:

• The relative physical activity question offered the optimal combination of reliability and validity.
• Single-item questions can serve as acceptable alternatives for measuring physical activity when detailed assessments are impractical.