[Characteristics of the number of steps in the National Health and Nutrition Survey].

OBJECTIVES

The mean number of steps measured in the National Health and Nutrition Survey is employed for the assessment of physical activity/exercise in "Health Japan 21," and is used to represent the amount of physical activity/exercise that citizens engage in. In this study, we clarified the characteristics of the data on the number of steps, drawn from the National Health and Nutrition Survey.

METHODS

Among the data from the National Health and Nutrition Surveys conducted from 2008 to 2010, data from 21,914 participants on daily number of steps and pedometer attachment were analyzed. On a nutritional intake questionnaire, subjects who responded on the physical status item that they had attached the pedometer all day long were assigned to the "Whole-day-attached" group. Their means, medians, outliers, and frequency distribution were then compared with those in a "Non- whole-day-attached" group.

RESULTS

Subjects assigned to the "Non- whole-day-attached" group accounted for about 8% of cases in 2008, 2009, and 2010. In all three years, the mean number of steps in the "Whole-day-attached" group was 1,076 to 1,472 higher than that in the "Non-whole-day-attached" group. In both groups, outliers were present, and the frequency distribution showed a broad range on the side indicating a higher number of steps. Accordingly, the mean value was higher than the median value by approximately 600 steps.

CONCLUSION

As data on the number of steps measured in the National Health and Nutrition Survey includes individuals not attaching the pedometer all day (approximately 8% of cases), the data are not normally distributed. Therefore, when utilizing these data as representative of citizens' physical activity/exercise, their characteristics should be taken into consideration.