Table 1.

Mean values and proportions for participant characteristics (n = 25,482).

	Total		Degree of loneliness							Frequency of feelings of increased social isolation during the COVID-19 pandemic
			None (3 points)		Mild (4–5 points)		Moderate-to-severe (6–15 points)		P for trend	Never		Rarely		Sometimes		Often		Always		P for trend
	n = 25,482		n = 14,277		n = 3250		n = 7955			n = 18,168		n = 3188		n = 2454		n = 1033		n = 639
	Mean	SD	Mean	SD	Mean	SD	Mean	SD		Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
	n	(%)	n	(%)	n	(%)	n	(%)		n	(%)	n	(%)	n	(%)	n	(%)	n	(%)
Age, years	48.8	17.3	51.5	17.3	50.3	17	43.3	16.2	< 0.001	50.7	17.1	48.1	17.3	42.2	16.3	38.5	15.5	38.2	14.4	< 0.001
Women	12,809	50.3	6794	47.6	1828	56.2	4187	52.6	< 0.001	8809	48.5	1778	55.8	1312	53.5	555	53.7	355	55.6	< 0.001
Body mass index  ≥ 25 kg/m2	4910	19.3	2864	20.1	543	16.7	1503	18.9	< 0.001	3611	19.9	566	17.8	431	17.6	173	16.7	129	20.2	0.001
Less than high school graduate	1014	4.0	540	3.8	93	2.9	381	4.8	< 0.001	718	4.0	93	2.9	116	4.7	45	4.4	42	6.6	< 0.001
Divorced	1602	6.3	841	5.9	212	6.5	549	6.9	0.01	1107	6.1	206	6.5	179	7.3	60	5.8	50	7.8	0.07
Living alone	4997	19.6	2431	17.0	644	19.8	1922	24.2	< 0.001	3260	17.9	688	21.6	599	24.4	283	27.4	167	26.1	< 0.001
Unemployed	3015	11.8	1708	12.0	374	11.5	933	11.7	0.72	2266	12.5	346	10.9	219	8.9	85	8.2	99	15.5	< 0.001
Living in poverty	1393	5.5	649	4.5	156	4.8	588	7.4	< 0.001	888	4.9	178	5.6	174	7.1	80	7.7	73	11.4	< 0.001
Current smoker	4581	18.0	2546	17.8	530	16.3	1505	18.9	0.004	3239	17.8	570	17.9	447	18.2	215	20.8	110	17.2	0.18
Heavy drinker	2144	8.4	1284	9.0	263	8.1	597	7.5	< 0.001	1620	8.9	238	7.5	164	6.7	72	7.0	50	7.8	< 0.001
Decreased physical activity during COVID-19 pandemic	7358	28.9	3774	26.4	1022	31.4	2562	32.2	< 0.001	4712	25.9	1180	37.0	766	31.2	429	41.5	271	42.4	< 0.001
Sleep duration < 6 h per night	6639	26.1	3312	23.2	716	22.0	2611	32.8	< 0.001	4223	23.2	862	27.0	927	37.8	381	36.9	246	38.5	< 0.001
Comorbid depression	969	3.8	172	1.2	66	2.0	731	9.2	< 0.001	378	2.1	157	4.9	181	7.4	147	14.2	106	16.6	< 0.001
Comorbid mental illnesses other than depression	950	3.7	182	1.3	58	1.8	710	8.9	< 0.001	371	2.0	158	5.0	173	7.0	130	12.6	118	18.5	< 0.001

COVID-19 coronavirus disease 2019, SD standard deviation.

Loneliness was measured using the Japanese version of the University of California, Los Angeles Loneliness Scale (Version 3), Short Form 3-item tool.

Poverty was defined as an equivalized income less than 1.22 million Japanese yen.

Individuals with alcohol consumption ≥ 46 g per day were defined as heavy drinkers.

P for trend values were calculated using a generalized linear model.