Decreased step count prior to the first visit for MDD treatment: a retrospective, observational, longitudinal cohort study of continuously measured walking activity obtained from smartphones

Abstract

Introduction: Major depressive disorder (MDD) is a common debilitating psychiatric condition and a major cause of productivity loss in workers. Using intermittent, subjective indicators, previous studies have shown that physical activity can predict lower levels of depressive symptoms. However, there is an unmet need for continuous and objective measures to identify MDD development before it results in productivity loss. The aim of this study was to elucidate the association between continuously measured walking activity and the development of MDD.

Methods: This retrospective, observational, longitudinal cohort study used health insurance claims data. Individuals aged 20-74 years were included if they had a record of MDD diagnosis and daily step count data for the 60 days before and after the first recorded MDD-related visit, which was defined as the index date. Multivariate analysis was conducted to compare 7-day moving averages of step counts on each day of the analysis period with the mean step count on the index date. Joinpoint regression analysis was used to determine when the trajectory of the moving step count average changed (inflection point).

Results: In total, 2,143 patients with a mean age of 41.2 (standard deviation [SD]: 10.6) years were included. The majority of patients were men (69.5%) and employed full-time (94.1%). Antidepressants were prescribed for 59.2% of patients. The 7-day moving average step count decreased from 6,310 (SD: 3758) at day -60 to 5,879 (SD: 3183) at the index date (first recorded MDD-related visit), and then increased to 6,062 (SD: 4029) at day +60. Compared with the index date, the 7-day moving average of step counts was significantly higher at days -60 to -1, +23 to +33, and + 42 to +60, and significantly lower at days +2 and + 3. Joinpoint regression analysis of 7-day moving average step counts from day -60 to day 0 identified an inflection point at day -14.

Conclusion: In working-age Japanese people, a formal diagnosis of MDD was preceded by a notable decline in daily step counts by approximately 2 weeks. MDD diagnosis and (presumed) treatment were followed by a gradual increase in daily step counts.

Keywords: Japanese; antidepressant; continuous monitoring; diagnosis; major depressive disorder; physical activity; step count.

Figure 1

Patients included in the analysis. MDD, major depressive disorder.

Figure 2

Multivariate analysis^a of moving average step counts^b before and after the index date^c. ^aCovariates were age, sex, year and month when step count data were acquired, participation in a walking campaign, hospitalization event, prescription of antidepressants during the analysis period and presence of comorbidity (coronary artery diseases, diabetes, stroke, chronic lower respiratory diseases, arthritis, hypertension, osteoporosis, fracture). ^bThe moving average of step counts was calculated after subtracting the number of steps on day 0 (i.e., the index date) from the 7-day moving average for each day at the individual level. ^cThe index date (day 0) was defined as the date of the first recorded MDD-related visit identified from health insurance claims data. ^dStep count changes around the index date were examined by inspecting the statistical significance of regression coefficients corresponding to each time point. MDD, major depressive disorder.

Figure 3

Results of joinpoint regression analysis. ^aSignificance level for individual test. ^bFinal selected model. *The slope is significantly different from 0 at the alpha level of 0.05.

Figure 4

Subgroup analyses in (A) patients <40 years old, (B) patients ≥40 years old, (C) men, (D) women, (E) patients on their own health insurance plan, and (F) patients on a family member’s health insurance plan as a dependent. ^aStep count changes around the index date were examined by inspecting the statistical significance of regression coefficients corresponding to each time point.

Figure 4

Subgroup analyses in (A) patients <40 years old, (B) patients ≥40 years old, (C) men, (D) women, (E) patients on their own health insurance plan, and (F) patients on a family member’s health insurance plan as a dependent. ^aStep count changes around the index date were examined by inspecting the statistical significance of regression coefficients corresponding to each time point.