Physical activity and regular exercise contribute to general health and mental well-being and are associated with reduced mortality.^1,2) On the other hand, prolonged sitting is associated with an increased risk of all-cause mortality, cardiovascular disease risk,³⁾ weight gain⁴⁾ or obesity,⁵⁾ metabolic syndrome,⁶⁾ type 2 diabetes,⁵⁾ and colon cancer.⁷⁾ Nevertheless, physical inactivity and prolonged sedentary lifestyles have gradually increased. Moreover, most of the elderly experience functional limitations and impairments that lead to a decrease in physical activity. A variety of studies have reported that physical activity and regular exercise for in the elderly have played an important role in improving quality of life⁸⁾ and slowing the gradual decline of bodily systems.⁹⁾

Until now, much attention has been paid on developing reliable and valid instruments to estimate activity levels and to measure the impact of intervention to promote physical activity.¹⁰⁾ The benefit in estimating physical activity is that it allows for early screening and prevention of decrease. Various tools for measuring physical activity include motion sensors such as pedometers and accelerometers or heart rate monitors, etc.^11,12)

But the preferred methods of measurement may not always be feasible to use because of cost and inconvenience. On the contrary, a simple and reliable questionnaire would have the advantages of low cost, convenience, and ease of various data collection. Self-reported questionnaires for measuring physical activity of the general population include the Health Insurance Plan of New York Activity Questionnaire,¹³⁾ the Baecke Questionnaire of Habitual Physical Activity,¹⁴⁾ the Lipid Research Clinics Questionnaire,¹⁵⁾ the Kuopio Ischaemic Heart Disease Risk Factor 24-hour Total Physical Activity Record,¹⁶⁾ and the Aerobic Center Longitudinal Study Physical Activity Questionnaire.¹⁷⁾

Of the many published questionnaires, the International Physical Activity Questionnaire (IPAQ) has been investigated and used in many populations. The IPAQ was developed by the World Health Organization in 1998 (http://www.ipaq.ki.se) for surveillance of physical activity and to facilitate global comparison. The IPAQ questions are adapted to cultural diversity, and use country-specific examples to help define physical activity and sitting. The 27-item long form and 7-item short form assess time spent on various activities. The 2 forms have been validated against accelerometer measurements as a gold standard in 12 countries. The short form is preferred by many researchers because it has equivalent psychometric properties to the long form.

The Korean version of IPAQ developed by Oh et al.¹⁸⁾ was recognized as a valid tool for physical activity assessment. Oh et al.¹⁸⁾ proved the reliability and the validity of the IPAQ short form. However, this study was examined for the subjects aged 15-69 and this report still lacks such confirmation in the elderly. The purpose of this analysis was to examine the reliability and the validity of the IPAQ short form in elderly people.

The decline in physical activity has important public health implications for older people, since there is increasing evidence that health effects of physical activity are linked specifically to the total amount of kilocalorie expenditure of activity time.²⁰⁾ The new Centers for Disease Control and Prevention/American College of Sports Medicine recommendations are especially useful for older people as they emphasize the value of moderate-intensity activity as well as the daily accumulations of physical activity. Thus the recommended accumulated expenditure of 200 kcal/d can be achieved easily by most older people through short bouts of activity such as stair climbing, gardening, walking, and playing with children or doing housework.²¹⁾ To apply these recommendations as a part of daily lifestyle, we need to measure the energy expenditure of physical activity first.

There have been many developments in physical activity questionnaires as simple and feasible measurements for the elderly such as the Modified Baecke Quesionnaire for older adults,²²⁾ the Zutphen Physical Activity Questionnaire,²³⁾ the Physical Activity Scale for the Elderly,²⁴⁾ the activity of daily living, the instrumental activity of daily living, and the Yale Physical Activity Survey.

But there are few physical activity questionnaires reflecting characteristics of physical activity in Korean elderly people. It may be most appropriate to use the existing questionnaires in Korea as well. However, their reliability must first be validated in older age groups.

Choe et al.²⁵⁾ developed a Korean version of the Physical Activity Scale for the Elderly (K-PASE) and reported K-PASE was a reliable and valid instrument to assess physical activity in Korean elderly. In this report, validity was established by correlating the K-PASE scores between the Tokyo Metropolitan Institute of Gerontology index of competence and hand-grip strength. However the Pearson's correlation coefficients were low.

The IPAQ has been recommended and widely used as a surveillance instrument but there have been arguments about its validity when comparing its measurements to objective measurements of physical activity.^26,27) Oh et al.¹⁸⁾ also reported the reliability and validity of the IPAQ short form in Korean people but the correlations were lower than that of other health variables. Spearman Rho coefficient was 0.267 for the correlation between the results of the questionnaire and measured values by accelerometer. The Spearman Rho coefficients and Kappa values of test-retest reliability were 0.427-0.646 and 0.365-0.620, respectively.¹⁸⁾ Although IPAQ had low correlations with the objective measurements, the IPAQ is one of the easiest of physical activity questionnaires to administer with less than 10 questions. Given the advantages of IPAQ, including its ease of administration and low cost, it seems worthwhile to use as a measurement of physical activity.

The IPAQ Korean version has been also used for the elderly. Park²⁸⁾ identified the relationship between physical activity measured by the IPAQ and sleep patterns of Korean elderly. Seo et al.²⁹⁾ suggested that physical activity measured by the IPAQ may be associated with cognitive function.

This cross-sectional study of elderly people in Seoul, Korea was performed to investigate the reliability and validity of the IPAQ short form. The IPAQ short form was validated against uni-axial accelerometer measurements as a gold standard. Although the uni-axial accelerometer underestimated the total daily energy expenditure, the energy expenditure measured by this showed correlation with other objective measurements.²⁰⁾ The correlation between two measurements was positively significant (Pearson's correlation coefficient, 0.43; P < 0.001). And the consistency of test and retest in five elements of IPAQ (vigorous days, vigorous minutes, moderate days, moderate minutes, and walking days) was fair to moderate. Two elements of IPAQ (walking minutes and sitting minutes) were not reliable. This low reliability may be caused by considerable daily variation according to health conditions in the elderly.

There were several limitations in this study. These data are likely to apply to individuals of low socioeconomic status who live in the city. They may have difficulty providing valid physical activity data, and data were more likely to be missing from those who lived in the country and had vigorous physical activity. A further limitation was the use of the accelerometer, as there may have been missing data of energy expenditure caused by measuring only uni-axial physical activity and inconvenience of wearing. The previous study showed that total energy expenditure measured by uni-axial accelerometer was significantly underestimated by a mean value of 8%. However, a highly significant relationship was demonstrated between the measured values by uni-axial accelerometer and those in the respiratory chamber.²⁰⁾

In conclusion, the validity of the IPAQ short form was demonstrated. However, the reliability was found to be low. Nevertheless, the IPAQ short form seems worthwhile to use as a tool for measuring physical activity levels in the elderly.