Background: Tracking refers to the tendency for an individual to maintain their rank within a group over time. This study longitudinally investigated the 8-year tracking of pedometer-determined physical activity among physically independent elderly Japanese people aged 72 to 80 years.
Methods: Steps/day were measured when participants were aged 72 and assessed again after 2, 5, and 8 years. The number of participants with a 2-year follow-up (72 to 74 years) was 177 (101 males, 76 females), with a 5-year follow-up (72 to 77 years) was 183 people (110 males, 73 females), and with an 8-year follow-up (72 to 80 years) was 145 people (91 males, 54 females). Step counts were continuously measured for 1 week in January, April, July, and October during each year of assessment.
Results: A high rank correlation coefficient for steps/day exceeding 0.60 was obtained at the 2-, 5- and 8-year follow-up examinations for both males and females.
Conclusion: This study suggests that the rank within a group of pedometer-determined steps/day remains stable over up to 8 years in healthy Japanese people aged between 72 to 80 years old.