Temporal association between physical restraint and venous thromboembolism risk among psychiatric inpatients: A matched case-control study

Table 1 Baseline demographic and clinical characteristics of cases and controls, n (%)

Variable	Cases (n = 127)	Controls (n = 423)	OR (95%CI)	P value
Sex
Female	68 (53.54)	211 (49.88)	1.00 (ref.)	-
Age (years)
≤ 40	32 (25.20)	132 (31.21)	1.00 (ref.)	-
41-60	52 (40.94)	180 (42.55)	1.90 (0.53-7.19)	0.31
61-74	34 (26.77)	84 (19.86)	6.50 (0.71-59.90)	0.10
≥ 75	9 (7.09)	27 (6.38)	2.20 (0.09-56.39)	0.63
BMI ≥ 30 kg/m²
Yes	2 (1.57)	17 (4.02)	0.37 (0.08-1.69)	0.20
Smoking
Yes	6 (4.72)	52 (12.29)	0.29 (0.11-0.76)	0.01
Current major depressive episode
Yes	8 (6.30)	21 (4.96)	0.96 (0.39-2.39)	0.94
Psychotropic medications
Antipsychotics (yes)	101 (79.53)	345 (81.56)	1.21 (0.66-2.21)	0.53
Antidepressants (yes)	31 (24.41)	75 (17.73)	1.24 (0.69-2.34)	0.47
Benzodiazepines (yes)	12 (9.45)	44 (10.40)	0.66 (0.28-1.52)	0.33
Hypertension
Yes	24 (18.90)	65 (15.37)	1.11 (0.61-2.02)	0.53
Active cancer
Yes	0 (0.00)	1 (0.24)	-	-
History of VTE
Yes	5 (3.94)	13 (3.07)	1.04 (0.72-1.49)	0.82
Reduced mobility
Yes	7 (5.51)	13 (3.07)	1.90 (0.75-4.82)	0.18
Thrombophilia
Yes	4 (3.15)	9 (2.13)	1.37 (0.38-4.98)	0.63
Recent trauma/surgery (≤ 1 month)
Yes	4 (3.15)	5 (1.18)	2.26 (0.60-8.58)	0.23
Heart/respiratory failure
Yes	0 (0.00)	5 (1.18)	-	-
Acute infection/rheumatic disease
Yes	0 (0.00)	6 (1.42)	-	-
Acute myocardial infarction/stroke
Yes	0 (0.00)	1 (0.24)	-	-
Hormonal therapy
Yes	0 (0.00)	3 (0.71)	-	-

Odds ratio for variables with zero events could not be estimated. OR: Odds ratio; CI: Confidence interval; VTE: Venous thromboembolism; BMI: Body mass index.

Table 2 Multivariable conditional logistic regression analyses for the association between physical restraint and venous thromboembolism, n (%)

Model	Cases (n = 127)	Controls (n = 423)	aOR (95%CI)
Model 1 PR exposure
PR (yes)	50 (39.37)	116 (27.42)	1.82 (1.16-2.85)
Model 2 PR duration in days
≤ 3	39 (30.71)	100 (23.64)	1.67 (1.04-2.70)
4-7	8 (6.30)	12 (2.84)	2.62 (0.93-7.40)
≥ 8	3 (2.36)	4 (0.95)	2.84 (0.52-15.65)
Model 3 cumulative PR hours
≤ 12	30 (23.62)	103 (24.35)	1.25 (0.75-2.08)
12-24	11 (8.66)	8 (1.89)	6.27 (1.98-19.90)
> 24	9 (7.09)	5 (1.18)	6.81 (1.92-24.36)
Model 4 interval between last PR and VTE diagnosis
≤ 7	37 (29.13)	34 (8.04)	5.29 (2.84-9.85)
8-14	3 (2.36)	31 (7.33)	0.38 (0.11-1.32)
≥ 15	10 (7.87)	51 (12.06)	0.82 (0.37-1.80)

All models were adjusted for age, body mass index, smoking status, use of antipsychotics, antidepressants, benzodiazepines, and venous thromboembolism-related risk factors with non-zero events. aOR: Adjusted odds ratio; CI: Confidence interval; PR: Physical restraint; VTE: Venous thromboembolism.