The relationship between pain severity and patient-reported outcomes among patients with chronic low back pain in Japan

Figures & data

Figure 1 Selection of respondents for the analysis.

Abbreviations: CLBP, chronic low back pain; LBP, low back pain; NHWS, National Health and Wellness Survey.

Table 1 Sociodemographic and health characteristics

	Diagnosed CLBP (N=290)
Age (years) (mean ± SD)	55.60±14.58
Female (%)	118 (40.69)
CCI (mean ± SD)	0.46±0.95
Employed (%)	161 (55.52)
Annual household income
<¥3 million (%)	48 (16.55)
¥3 million to <¥5 million (%)	81 (27.93)
¥5 million to <¥8 million (%)	76 (26.21)
¥8 million or more (%)	70 (24.14)
Decline to answer (%)	15 (5.17)
Married/living with partner (%)	211 (72.76)
University education or higher (%)	140 (48.28)
BMI category
Underweight (%)	21 (7.24)
Normal weight (%)	200 (68.97)
Overweight (%)	56 (19.31)
Obese (%)	9 (3.10)
Decline to provide weight (%)	4 (1.38)
Smoking
Never smoked (%)	107 (36.90)
Former smoker (%)	105 (36.21)
Current smoker (%)	78 (26.90)
Drink alcohol (%)	215 (74.14)
Vigorous exercise at least 1 day in the past month (%)	134 (46.21)

Abbreviations: BMI, body mass index; CCI, Charlson comorbidity index; CLBP, chronic low back pain; SD, standard deviation.

Table 2 Pain characteristics

	Diagnosed CLBP (N=290)
Severity of LBP
Mild (%)	78 (26.90)
Moderate (%)	161 (55.52)
Severe (%)	51 (17.59)
Severity of pain in the past week (0–10) (mean ± SD)	4.92±2.45
Current severity of pain (0–10) (mean ± SD)	5.20±2.31
Frequency of problems with pain
Once a month or less often (%)	12 (4.14)
2–3 times a month (%)	28 (9.66)
Once a week (%)	31 (10.69)
2–3 times a week (%)	59 (20.34)
4–6 times a week (%)	25 (8.62)
Daily (%)	135 (46.55)
Type of diagnosing doctor for LBP
Orthopedist (%)	246 (84.83)
General internist (%)	18 (6.21)
Pain management specialist (%)	3 (1.03)
Rheumatologist (%)	1 (0.34)
Other (%)	22 (7.59)
Duration of LBP (in months) (mean ± SD)	115±122
Current use of a prescription medication for pain (%)	120 (41.38)
NSAIDs (%)	82 (68.33)
Opioid (%)	18 (15.00)
Pregabalin (%)	10 (8.33)
Antidepressant (%)	3 (2.50)
Other (%)	25 (20.83)
Use of an OTC product for pain (%)	76 (26.21)

Abbreviations: CLBP, chronic low back pain; LBP, low back pain, NSAIDs, nonsteroidal anti-inflammatory drugs; OTC, over-the-counter; SD, standard deviation.

Table 3 Spearman correlation coefficients between pain in the past week and outcomes

	rs	P-value
MCS	−0.25	<0.0001
PCS	−0.47	<0.0001
Health utility score (SF-6D)	−0.38	<0.0001
Depression severity (PHQ-9)	0.26	<0.0001
Anxiety severity (GAD-7)	0.23	<0.0001
Absenteeism % (n=155)	0.32	<0.0001
Presenteeism % (n=155)	0.51	<0.0001
Overall work impairment % (n=155)	0.52	<0.0001
Activity impairment %	0.52	<0.0001
HCP visits in the past 6 months	0.23	<0.0001
ER visits in the past 6 months	0.12	0.035
Hospitalizations in the past 6 months	0.02	0.714

Abbreviations: ER, emergency room; GAD-7, Generalized Anxiety Disorder-7; HCP, health care provider; MCS, mental component summary; PCS, physical component summary; PHQ-9, Patient Health Questionaire-9; SF-6D, Short-Form 6D.

Table 4 Regression-adjusted outcomes according to the level of pain in the past week

Dependent variable	Patients inregressionanalysis	P-value for pain in the past week	Regression-estimated outcome values at levels of pain in the past week
			At 25th percentile (3/10); mild	At median (5/10); moderate	At 75th percentile (7/10); severe
MCS	290	<0.001	47.1	45.1	43.2
PCS	290	<0.001	48.5	45.7	43.0
Health utility score (SF-6D)	290	<0.001	0.70	0.67	0.63
Depression severity (PHQ-9)	290	<0.001	3.3	4.1	5.3
Anxiety severity (GAD-7)	290	<0.001	3.2	3.8	4.7
Absenteeism	155	0.003	0.7%	2.0%	5.8%
Presenteeism	155	<0.001	17.8%	27.6%	42.9%
Overall work impairment	155	<0.001	19.2%	30.5%	48.4%
Activity impairment	290	<0.001	22.0%	31.7%	45.7%
HCP visits in the past 6 months	290	0.007	10.4	12.1	13.9
ER visits in the past 6 months	290	0.189	0.05	0.07	0.11
Hospitalizations in the past 6 months	290	0.705	0.21	0.25	0.29

Notes: Values are presented at the mean of the covariates. Covariates included duration of CLBP, age, sex, Charlson comorbidity index, annual household income, marital status, completion of a university degree, body mass index category, smoking status, alcohol use, and exercise in the prior month.

Abbreviations: CLBP, chronic low back pain; ER, emergency room; GAD-7, Generalized Anxiety Disorder-7; HCP, health care provider; MCS, mental component summary; PCS, physical component summary; PHQ-9, Patient Health Questionaire-9; SF-6D, Short-Form 6D.