Failure to validate the Health Survey for England physical activity module in a cardiac population

Abstract

Objectives The Health Survey for England physical activity module interview, although not validated, is used as a performance indicator to see if people are achieving current physical activity targets and is the primary source of information for physical activity related policy making. The aim of this study was to assess the validity of the Health Survey for England physical activity module as a measure of physical activity in older adults with coronary heart disease. Methods Seventy-two older adults who had experienced a cardiac event completed the Health Survey for England physical activity interview and wore an accelerometer for seven consecutive days. Physical activity classification levels were derived from accelerometry and from the Health Survey for England physical activity interview, together with the number of episodes in which participants were moderately active for 30 min or more. Results The Health Survey for England physical activity interview exhibited high sensitivity (1.0) and specificity (0.76) for people engaged in high levels of physical activity, moderate sensitivity (0.40) and specificity (0.56) for people engaged in medium levels of physical activity and low sensitivity (0.35) and high specificity (0.92) for people engaged in low levels of physical activity. Compared with the accelerometer, the survey misclassified 63% of participants. Conclusions The Health Survey for England physical activity interview misclassified true activity levels in older adults with heart disease by overestimating actual activity in the less active participants. Similar biases on self-report physical activity measures have been demonstrated in the general population, suggesting that the Health Survey for England physical activity module interview may be providing inaccurate information on national activity levels.