September 20, 2022Open Access
Understanding of the Single-Item Physical Activity Question for Population Surveillance
Structured PICO
Does the single-item days per week question accurately reflect meeting physical activity guidelines compared to IPAQ and SI-hours questions in a population survey?
P
Population
13,887 participants in the representative 'Active NZ' surveys between 2019 and 2020
I
Intervention
Single-item days (SI-days) per week physical activity question
C
Comparator
International Physical Activity Questionnaire (IPAQ)-long-form and single-item hours (SI-hours) per week question
O
Outcome
Relationship between the established SI-days question and meeting physical activity guidelines (150 min moderate-to-vigorous physical activity per week)patient reported
The single-item days per week question is a valid measure for physical activity surveillance, with a cut point of at least 3 days per week best reflecting the achievement of physical activity guidelines.
Abstract
BACKGROUND: Sport New Zealand conducts continuous representative "Active NZ" surveys. Between 2019 and 2020 (n = 13,887), these surveys asked International Physical Activity Questionnaire (IPAQ)-long-form questions, the single-item days (SI-days) per week question, and 1 question on hours per week (single-item hours SI-hours per week). This study examines relationships between the established SI-days question and meeting physical activity (PA) guidelines (150 min moderate-to-vigorous physical activity per week from SI-hours question and IPAQ). METHODS: Analyses were descriptive, and the best fit between SI-days and the PA thresholds was estimated using area under the receiver operator characteristic curves and Youden index. RESULTS: Using SI-hours, 60.6% achieved 150+ minutes; 85.2% reported the IPAQ-total minimum threshold, and 40.8% met the IPAQ-leisure time PA-only threshold. Receiver operator characteristic analyses showed area under the curve values with IPAQ between 0.63 and 0.76, but the SI-days showed a very good area under the curve of 0.82 (0.81-0.83) with the SI-hours 150-minute threshold. Youden index suggested the best fit was at 3+ days per week for maximizing Sensitivity and Specificity to meet IPAQ or SI-hours-defined PA guidelines. DISCUSSION: The SI-days per week question reflects achieving PA guidelines, and the best fit was with the SI-hours per week question. This provides surveillance-relevant concurrent validity for the SI-days measure, but the cut point for broadly meeting guidelines appears to be at least 3 days per week, not 5 days per week as previously thought.