# Different associations of stay-at-home exposure with changes in body mass index and cardiometabolic factors depending on occupational physical activity: a longitudinal quasi-experimental design

## TL;DR

Forced work interruptions caused significant weight gain and higher blood pressure in physically active workers, but not in sedentary workers.

## Contribution

This study provides novel evidence that workers with physically demanding jobs are more vulnerable to metabolic health declines during forced work stoppages.

## Key findings

- High-intensity workers gained more BMI during a 4-month work suspension compared to sedentary workers.
- A dose–response relationship was observed between days absent and BMI increase in physically demanding jobs.
- Systolic blood pressure increased in medium- and high-intensity workers during the suspension.

## Abstract

To quantify the short-term impact of an unexpected stay-at-home exposure, caused by a shipment suspension, on body mass index (BMI) and cardiometabolic markers among employees with different levels of occupational physical activity.

Health-check records from 8307 workers at a large Japanese automobile manufacturer were linked to company attendance data covering a shipment suspension (January to April 2024). An interrupted time-series assessed BMI trajectories before, during, and after the halt. Among 614 employees who underwent an additional examination in April 2024, mixed-effects models related the duration of stay-at-home to changes in BMI and blood pressure within low-, medium-, and high-intensity job categories.

Compared with pre-halt trends, medium-intensity and high-intensity workers showed significant level rises in BMI (0.96 kg/m2; 95% CI, 0.56-1.36; and 0.64 kg/m2; 95% CI, 0.24-1.04, respectively) at the onset of the suspension. Mixed-effects analyses showed a positive dose–response between the duration of stay-at-home and BMI gain in high-intensity jobs (0.47 kg/m2 per 20% absent days; 95% CI, 0.37-0.58). Per 20% of scheduled workdays absent, systolic blood pressure was higher in the medium- and high-intensity groups. No significant effects were observed among sedentary workers.

Employees whose daily energy expenditure relies on job-related physical activity are especially susceptible to weight gain and blood pressure elevations during forced work interruptions. Business continuity plans should embed tailored countermeasures—such as structured exercise programs and phased returns to on-site duties—to safeguard metabolic health during future operational disruptions.

Key points:
What is already known on this topic: Pandemic-era studies have suggested that stay-at-home orders reduce physical activity and promote weight gain, but evidence is scarce for manual-labor employees whose daily energy expenditure depends on their jobs; previous analyses were confounded by infection-control policies.What this study adds: Exploiting an unexpected 4-month shipment suspension at a Japanese automobile plant, this interrupted time-series and mixed-effects analysis of 8307 workers showed that BMI and systolic blood pressure rose most sharply among high-intensity (physically demanding) occupations, with a dose–response relationship between days absent and cardiometabolic deterioration, whereas sedentary workers were largely unaffected.How this study might affect research, practice, or policy: The findings indicate that business continuity and occupational health plans should embed targeted countermeasures—structured at-home exercise, phased on-site returns, rotating shifts, and stress-management resources—to preserve metabolic health during future work stoppages. We provide a quasi-experimental framework for evaluating such interventions.

What is already known on this topic: Pandemic-era studies have suggested that stay-at-home orders reduce physical activity and promote weight gain, but evidence is scarce for manual-labor employees whose daily energy expenditure depends on their jobs; previous analyses were confounded by infection-control policies.

What this study adds: Exploiting an unexpected 4-month shipment suspension at a Japanese automobile plant, this interrupted time-series and mixed-effects analysis of 8307 workers showed that BMI and systolic blood pressure rose most sharply among high-intensity (physically demanding) occupations, with a dose–response relationship between days absent and cardiometabolic deterioration, whereas sedentary workers were largely unaffected.

How this study might affect research, practice, or policy: The findings indicate that business continuity and occupational health plans should embed targeted countermeasures—structured at-home exercise, phased on-site returns, rotating shifts, and stress-management resources—to preserve metabolic health during future work stoppages. We provide a quasi-experimental framework for evaluating such interventions.