Background: This secondary analysis investigated the extent and pattern of one-year tracking of pedometer-determined physical activity in people who relocated within the same metropolitan area (T1: baseline and T2: post-relocation). Specifically, data were derived from the RESIDential Environment Project (RESIDE), a natural experiment of people moving into new housing developments.
Methods: 1,175 participants (491 males, age = 42.6 +/- 12.7 years, BMI = 27.2 +/- 9.9 kg/m2; 684 females, age = 41.2 +/- 11.3 years, BMI = 25.4 +/- 5.2 kg/m2) wore a Yamax pedometer (SW-200-024) for seven days during the same season at both time points. Pearson's product-moment and Spearman's rank order correlations were used to evaluate the extent of tracking of mean steps/day. Age categories were set as youngest-29.9 (19 was the youngest in males, 20 in females), 30-39.9, 40-49.9, 50-59.9, and 60-oldest (78 was the oldest in males, 71 in females). Change in steps/day was also described categorically as: 1) stably inactive < 7,500 steps/day; 2) decreased activity (moved from > or = 7,500 to < 7,500 steps/day between T1 and T2); 3) increased activity (moved from < 7,500 to >/= 7,500 steps/day between T1 and T2); and, 4) stably active > or = 7,500 steps/day at both time points. Stratified analyses were used to illuminate patterns by sex, age, and BMI-defined weight categories.
Results: Overall, there was a small (non-significant) decrease in steps/day between T1 and T2 (mean +/- SD is -81 +/- 3,090 with 95%CI -259 to 97). With few exceptions (i.e., older women), both Pearson's and Spearman's correlations were moderate (r = 0.30-0.59) to moderately high (r = 0.60-0.70). The relative change/stability in steps/day (cut at 7,500 steps/day) was not significant across age groups in males (chi2 = 17.35, p = .137) but was in females (chi2 = 50.00, p < .0001). In both males and females the differences across BMI categories was significant (chi2 = 22.28, p = .001 and chi2 = 15.70, p = .015, respectively). For both sexes, those in the obese category were more stably inactive (and less stably active) between assessment points compared with those who were categorized as normal weight.
Conclusion: Despite relocation, Western Australian adults held their rank position to a moderate to moderately high extent over one year. Categorized and expressed as relative stability/change over time, sex, age, and BMI patterns were evident.