Table 2.

Association between increased work from home and LBP during the COVID-19 pandemic among the desk workers.

		Model 1	Model 2
		OR (95%CI)	OR (95%CI)
Working from home has increased	Yes	2.12 (1.56–2.88)	2.13 (1.52–2.97)
	No	Ref.	Ref.
Age (years)	18–29	1.06 (0.68–1.66)	1.04 (0.61–1.77)
	30–44	1.33 (0.95–1.86)	1.28 (0.89–1.843)
	45–59	Ref.	Ref.
Sex	Female	1.00 (0.73–1.38)	1.38 (0.95–2.01)
	Male	Ref.	Ref.
Overweight or obese 1	Yes		0.97 (0.64–1.47)
	No		Ref.
Educational attainment	College or higher		1.23 (0.79–1.90)
	High school or lower		Ref.
Marital status	Never married		0.95 (0.57–1.57)
	Married		Ref.
	Widowed or separated		0.78 (0.36–1.66)
Have children	Yes		1.71 (1.10–2.66)
	No		Ref.
Outdoor exercise during the COVID-19	Yes		1.32 (0.95–1.82)
pandemic	No		Ref.
Duration of the COVID-19 state of	Long		1.20 (0.82–1.74)
emergency in Japan 2	Medium		1.15 (0.70–1.90)
	Short		Ref.
Employment status	Employer		1.31 (0.71–2.40)
	Self-employed		0.97 (0.50–1.88)
	Regular employee		Ref.
	Non-regular employee		0.56 (0.32–0.98)
Income level	Low		1.42 (0.89–2.25)
	Intermediate		Ref.
	High		0.75 (0.50–1.13)
	Not answered		0.70 (0.39–1.26)
Working time (hours per week)	<35		1.79 (1.04–3.08)
	35–39		Ref.
	40–44		0.82 (0.48–1.43)
	>45		1.30 (0.76–2.20)
Smoking status	Never		Ref.
	Former		1.72 (1.15–2.56)
	Current		1.46 (0.97–2.19)
Alcohol use	Never		Ref.
	Former		0.97 (0.60–1.58)
	Current		0.95 (0.59–1.52)
Comorbidities	Hypertension		1.43 (0.87–2.36)
	Diabetes		1.45 (0.72–2.92)
	Asthma or COPD		1.26 (0.61–2.61)
	Cardiovascular disease		1.44 (0.45–4.58)
	Stroke		0.37 (0.08–1.72)
	Cancer		3.45 (1.25–9.50)
	Psychiatric disorders		2.33 (1.36–4.01)

LBP, low back pain; COVID-19, coronavirus disease 2019; COPD, chronic obstructive pulmonary disease; OR, odds ratio; CI, confidence interval. ¹ Defined as BMI > 25. ² Divided into three categories as follows. Long: seven prefectures with the longest emergency declarations due to COVID-19; medium: six prefectures with the second longest emergency declarations due to COVID-19; and short: thirty-four prefectures with the shortest emergency declarations due to COVID-19. Model 1: adjusted for age and sex. Model 2: in addition to Model 1, adjusted for overweight or obesity, educational attainment, marital status, having children, outdoor exercise during the COVID-19 pandemic, psychological distress, smoking status, alcohol use, comorbidities, employment, income level, and working time. Pseudo-R² statistics R² (Model 1) = 0.018 R² (Model 2) = 0.082.