There is substantial evidence that a physically active lifestyle is important for maintaining health and functional ability in older populations. Epidemiological studies have shown that physical inactivity is associated with an increased risk of all-cause mortality (1) and cardiovascular morbidity in older adults (12). Habitual physical activity in elderly cohorts has also been related to decreased risk for falls and hip fractures (11,24), declines in bone mass (30), and muscular strength (25).
Many self-reported physical activity questionnaires have been developed for large-scale epidemiological studies (19). Given the variety of data formats provided by the different questionnaires, it is difficult to compare results among different studies across countries. In response to the demand for a comparable and valid instrument, the World Health Organization (WHO), the U.S. Centers for Disease Control and Prevention (CDC), and other partners have developed the International Physical Activity Questionnaire (IPAQ; see www.ipaq.ki.se) for assessing physical activity levels across populations and countries. The validity and reliability of the IPAQ has been tested in 12 countries (6), as well as in Hong Kong Chinese (ages 15-55 yr) (18), but both studies used predominantly young (age < 55 yr) and well-educated participants. Our previous experience (17,18) has shown that cultural and language differences can exist when an English-based questionnaire is translated into a local dialect. It was therefore not known how a predominantly older and less educated group of Mainland Chinese would respond to the IPAQ. Furthermore, no internationally published data are available describing the use of the IPAQ in Mainland Chinese populations, or in older adults. Because walking is one of the most common types of physical activity, pedometry has become increasingly popular for measurements of physical activity. Thus, the purpose of this study was to examine the validity and reliability of Chinese version of the IPAQ (IPAQ-C) in a group of older Mainland Chinese, using pedometry-measured activity as the objective criterion.
The Guangzhou Biobank Cohort Study (GCBS), a three-way collaboration among Guangzhou, Hong Kong, and Birmingham, was initiated in 2003, with the aim of investigating genetic, lifestyle, occupational, and environmental determinants of common chronic diseases in an older Chinese population (10). To date, 20,440 participants (14,556 women, 5884 men, ages ≥ 50 yr) have been recruited from the Guangzhou Health and Happiness Association for the Respectable Elders (GHHARE). The GHHARE, aligned with the municipal government, is a large organization with branches throughout Guangzhou and membership open to anyone 50 yr of age or older, for a nominal annual fee of 48 Yuan ($6.00). It is a citywide network with around 95,000 permanent members, which represents approximately 7% of the ≥ 50-yr age strata, providing a good sampling frame for the GCBS and the present study.
In this study, a total of 230 eligible participants (66.1% women, 33.9% men, ages ≥ 50 yr) were randomly selected from the GCBS on the basis of their research identity number, using a random list generator in a manner that was blinded to any personal identifiers. Those with a physical disability limiting their ability to manipulate the pedometer (and, thus, limiting their ability to participate in the study), or those incapable of providing consent, were not recruited to the study. The study was approved by the Guangzhou medical ethics committee of the Chinese Medical Association, Guangzhou, China.
Measurements of Physical Activity
The IPAQ is used to assess habitual physical activity participation during the previous 7 d. There are two versions, the long (31 items) and short (9 items), which can be self-administered or administered during in-person or telephone interviews. The short version was designed for population surveillance and large-scale studies of physical activity, whereas the long version focused on providing more detailed information as an evaluation tool in research. The IPAQ-C used in the present study is the short Chinese version originally translated by Macfarlane et al. (18) according to the procedures recommended by the International Consensus Group for the Development of the IPAQ, involving translation with back-translation from the original English version and appropriate cultural adaptations. This short version asks the participants to report the frequency and duration of walking, all vigorous and moderate activities lasting at least 10 min, plus time spent in sedentary activity (sitting and lying awake). The IPAQ-C data were converted to metabolic equivalent scores (MET·min·wk−1) for each type of activity. The MET score weights each type of activity by its energy expenditure, using 1 MET for sitting, 3.3 METs for walking, 4 METs for moderate activity, and 8 METs for vigorous activity (see www.ipaq.ki.se).
The pedometers (Yamax SW-200, 200, Yamax, Tokyo, Japan) used in the present study were electronic motion sensors, which respond to vertical accelerations of the human body such as walking and running. The pedometer was worn on the waistband in the midline of the thigh, and any movement detected above a specific threshold was recorded as a completed "step" taken. The validity and reliability of the Yamax pedometers have been tested in populations ranging in age from 7 to 74 yr (7,20,26). When compared with other brands, the Yamax pedometers performed better in step counting and distance estimation (20), even in subjects displaying a wide range of body mass index (BMI) values (23).
Before commencement of the present study, all research nurses were trained to conduct the physical examination and administer the IPAQ-C in a standardized manner. On day 1, after informed written consent was obtained, the participants received a physical examination by trained research nurses, including measurement of blood pressure, waist and hip circumferences, height, weight, and percent body fat (Tanita BF350, Tanita Inc., Japan). All participants completed the IPAQ-C, administered by the nurses. A pedometer and log sheet with photos showing the appropriate placement of the pedometer were provided to each participant, each of whom was carefully instructed on how to wear the pedometer on the waistband in the midline of the right/left thigh for the whole day, except when sleeping, showering/bathing, or swimming, during the 7-d period. They were asked to reset the pedometer to zero each morning and to write down their day-end steps on the log sheets every evening before going to bed. After the 7-d pedometer measurement, participants were invited to attend the clinic on day 9, when the IPAQ-C was readministered. Data from the IPAQ-C (day 9) were compared with the same 7 d of pedometer-measured steps, to determine the criterion validity of this questionnaire.
Participants with 1 d or more of missing values were excluded from the analyses. Descriptive characteristics were reported as means ± standard deviations or as percentages. BMI was calculated using weight in kilograms divided by height in meters squared. Waist-to-hip ratio was calculated using waist circumference divided by hip circumference. Median and range were also presented for the physical activity data because of their skewed distributions. The Student's independent t-test was used to compare differences in continuous variables, and the chi-square test was used for categorical variables. Test-retest reliability was assessed by a single-measure intraclass correlation coefficient (ICC, one-way random-effects model). To determine the criterion validity of the IPAQ-C, Spearman correlation coefficients were used to compare pedometer-measured steps with data (MET·min·wk−1) from the IPAQ-C on day 9. Because gender, age, and education may affect the correlations between self-reported and objective measures of physical activity, partial correlations were used to control for the effects of these factors (9). All data analyses were performed using the Statistical Package for the Social Science (SPSS for Windows 14.0, SPSS Inc., Chicago, IL).
Two hundred twenty-four participants (ages 51-82 yr) were included in the present analyses. Six women were excluded because of incompleteness of their pedometer records. The participants in present study were predominately women (66.1%), which reflects the proportion of men and women in the GBCS. Men and women were similar in BMI and systolic and diastolic blood pressures. Women were significantly younger, had less education, and had a higher percent body fat than men (Table 1).
Table 2 shows that both women and men were physically active in terms of total activity measured by the IPAQ-C (4583 ± 1786 MET·min·wk−1 for day 1 and 4748 ± 808 MET·min·wk−1 for day 9) and steps recorded by pedometers (69,390 ± 20,602 steps per week). Women reported 14% more walking than men for mean MET-minutes per week in the IPAQ-C; however, there were no significant differences between men and women for pedometer-measured steps (although women had 5% more steps) or for other domains of the IPAQ-C. On the basis of energy expenditure estimated by the IPAQ-C, walking was the most common form of activity, which contributed approximately three quarters of the total MET counts. This high level of self-reported walking activity was consistent with the steps counted by pedometers, averaging 10,069 ± 2794 steps for women and 9609 ± 3212 steps for men each day.
The test-retest reliabilities of the IPAQ-C are shown in Table 3. The intraclass correlation coefficient (ICC) for each domain of the IPAQ-C between day 1 and day 9 ranged from 0.81 to 0.89, which was highly significant (P < 0.001) (13). The ICC was greatest for the sitting domain (0.89, 95% CI: 0.86-0.91) and lowest for moderate activity (0.81, 95% CI: 0.76-0.85).
Total activity (excluding sitting) measured by the IPAQ-C was moderately related to the pedometry data (Spearman and partial r = 0.33, P < 0.001), and the agreement between walking domain of the IPAQ-C and steps taken was good (Spearman r = 0.51, P < 0.001). After adjustment for sex, age, and education, the correlation became slightly greater (partial r = 0.58, P < 0.001). No significant correlations were observed between pedometer-measured steps and other domains of the IPAQ-C, namely vigorous, moderate, and sedentary activity (Table 4).
As populations age, particularly in developing countries, effective approaches to help older people maintain a healthy and active life are urgently needed. Physical activity has been shown to improve quality of life in later years by reducing morbidity (2,12,21) and disability (14). China is the most populated country in the world, with approximately 113 million of older adults ages 65 yr or above (5). Despite considerable research findings showing the beneficial effects of physical activity, currently there are only five well-known validated questionnaires for assessment and surveillance of physical activity in older populations (3,8,22,27,28), and none are culturally specific for older Chinese. To the best of our knowledge, this is the first study examining the reliability and validity of an international standardized questionnaire (IPAQ-C) in a large sample of older Chinese. We found that the IPAQ-C showed good test-retest reliability with all ICC greater than 0.80. There was also no significant change in reported activity measures using the IPAQ-C on day 1 compared with day 9, indicating minimal reactivity during the 7 d of consecutive measurement. The reliability of our short version of IPAQ-C was comparable with the original reliability studies of IPAQ (6).
When compared with the objective pedometry data, the IPAQ-C showed moderate validity in assessing total physical activity, and, as expected, the walking domain of the IPAQ-C correlated highly with pedometer-measured steps. This is of particular importance in Chinese populations, where walking is a major form of energy expenditure. A provincial survey from Guangdong supports the observation that the most common type of physical activity in the older population is walking (74.5%) (16), and this finding is supported in our study. There was no statistically significant correlation found between the amount of vigorous and moderate activity estimated by the IPAQ-C and the number of steps taken from the pedometer. This may be partly attributable to the design of the pedometer, which is good for detecting moderate- to low-level activity such as walking but cannot differentiate this from more moderate-to-vigorous activities such as running. Because the pedometer also does not measure sitting, we found no association (r < 0.01) between the IPAQ-C sitting domain and pedometer-measured steps, adding to the robustness of our findings. In general, there are four types of objective measurements used to assess habitual physical activity: doubly labeled water, calorimetry, heart rate monitoring, and motion sensors, such as accelerometers and pedometers. Because physical activity is considered to be "any bodily movement … that results in caloric expenditure" (4), doubly labeled water and calorimetry can quantify physical activity by measuring true levels of energy expenditure, and, thus, they are recognized as the best approaches for physical activity assessment. However, these methods are not feasible in large epidemiological studies, because of the high costs and logistical difficulties. Heart rate monitoring measures the relative stress placed on the cardiovascular system by physical activity. This method is good at quantifying moderate-to-vigorous activity, but relatively poor in measuring low-intensity activities (15), and, therefore, it is less suited for physical activity assessment in most older populations. It is also more expensive and inconvenient than pedometry.
Both accelerometers and pedometers monitor physical activity by recording movement accelerations of human body. Accelerometers typically detect movements in either one or three dimensions by using piezoelectric transducers and microprocessors to measure intensity and quantity of the movement. The accelerometers most commonly used as criterion references in physical activity research are of the uniaxial rather than triaxial type, because they can still quantify most movements and estimate intensity of physical activity; however, like most accelerometers, they cannot distinguish intensities during walking uphill, cycling, or upper-body exercise (29). As with doubly labeled water and calorimetry, the high cost of most accelerometers, ranging from $200 to $500, limits their use to relatively small studies. A recent review on the utility of pedometers indicates that physical activity measures based on pedometry correlated very strongly (median r = 0.86) with those derived from accelerometers, suggesting that pedometry might be a suitable proxy for accelerometry (26). More recently, a study on the convergent validity of six physical activity assessments has confirmed that pedometers gave an assessment of total activity similar to that provided by accelerometry in monitoring total activity (17). Given the low cost ($10-$16) and accuracy of some models (7), pedometers seem to be an optimal objective method to assess physical activity in developing countries like China. Because walking is the predominant measurable form of energy expenditure in older Chinese subjects, we believe that pedometry is well-suited as a criterion reference, and its limitations, such as not measuring intensity, are not likely to have significantly affected its capacity in measuring and monitoring the total physical activity of our participants.
This is the first reported validation study of an international standardized questionnaire (IPAQ-C) in older Chinese. The high intraclass correlation coefficients indicate that the IPAQ-C is adequately reliable, whereas the significant correlations between steps accrued via pedometry and the IPAQ-C estimation of walking and total physical activity expenditure support its validity. In conclusion, the IPAQ-C is a useful instrument for generating internationally comparable data on habitual physical activity in this population.
The study was funded by Hong Kong University Research Committee (URC) Strategic Research Themes on Public Health, and The University of Hong Kong Foundation for Educational Development and Research, Hong Kong; Guangzhou Public Health Bureau, and Guangzhou Science and Technology Bureau, Guangzhou, China; and The University of Birmingham, UK. We would like to thank all participants in this study, and Ms. W.D. Zhai from the Guangzhou Health and Happiness Association for the Respectable Elders (GHHARE) for recruiting the subjects. The Guangzhou Biobank Cohort Study investigators include X.Q. Lao, W.S. Zhang, B. Liu, C.Q. Jiang (Co-PI); The University of Hong Kong: G.N. Thomas, C.M. Schooling, S.M. McGhee, R.F. Fielding, G.M. Leung, T.H. Lam (Co-PI); The University of Birmingham: P. Adab, K.K. Cheng (Co-PI). The results of the present study do not constitute endorsement by ACSM.
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