Tracking of pedometer-determined physical activity in adults who relocate: results from RESIDE

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.