Table 1.

Characteristics of Medicare Beneficiaries Initiating Opioids or Gabapentinoids and by Trajectory Group

Characteristics	Overall	OPI Only			GABA only			OPI-GABA				SMDb before IPTW	SMDb after IPTW
		Aa	Ba	Ca	Da	Ea	Fa	Ga	Ha	Ia	Ja
No. beneficiaries	71,005	28,842	11,793	1,284	8,854	7,802	2,179	4,786	2,408	2,303	664
% of the overall cohort	100	40.6	16.6	1.8	12.5	11.0	3.1	6.9	3.4	3.2	0.9
Disease status, %
Any low back pain	78.5	73.6	79.5	91.7	81.2	79.5	82.2	82.0	90.2	85.8	94.3	0.22	0.08
Any osteoarthritis	70.9	73.4	73.0	55.3	68.7	70.4	62.1	69.8	67.8	65.5	61.0	0.15	0.07
Any fibromyalgia	20.2	14.4	18.7	31.1	24.5	25.1	28.7	22.7	32.1	31.0	38.0	0.20	0.04
Any neuropathy	19.7	13.9	13.1	10.3	24.2	34.5	32.6	27.3	22.8	31.9	21.2	0.26	0.06
Socio-demographics
Age, mean (SD)	65.5 (14.5)	68.3 (13.8)	64.0 (14.6)	54.1 (3.2)	65.6 (14.8)	65.6 (13.9)	59.8 (13.7)	66.0 (13.8)	59.1 (14.5)	58.9 (13.4)	52.3 (12.3)	0.48	0.19
Female, %	68.1	69.9	64.7	52.0	69.9	70.3	61.6	71.0	64.8	65.4	54.1	0.16	0.07
Race/ethnicity, %												0.20	0.09
White	76.8	76.4	80.2	87.7	72.4	73.8	82.9	73.1	78.5	82.5	85.8
African American	13.5	13.5	13.5	8.6	14.4	14.1	10.1	14.4	15.4	10.6	8.3
Hispanic	3.8	4.0	2.5	1.4	5.3	5.1	2.4	5.0	2.2	2.1	2.3
Others	5.9	6.1	3.8	2.3	8.0	6.9	4.5	7.6	4.0	4.9	3.6
Disability status, %	39.3	28.9	43.8	75.3	42.5	44.3	58.0	34.0	57.6	56.9	81.9	0.44	0.08
LIS/dual eligibility, %												0.14	0.06
LIS and dual eligibility	44.1	38.9	44.4	41.8	50.0	53.9	50.3	41.9	47.9	45.8	45.0
LIS or dual eligibility	6.6	5.9	6.7	8.1	7.5	7.4	8.2	7.5	7.1	7.1	8.1
No LIS/dual eligibility	49.3	55.1	49.0	50.1	42.4	38.7	41.5	44.7	44.7	47.1	46.8
Health status factors
Elixhauser index, mean (SD)	2.7 (2.3)	2.7 (2.2)	2.5 (2.4)	1.4 (19)	2.9 (2.3)	2.9 (2.5)	2.9 (2.5)	2.7 (2.3)	2.3 (2.3)	2.4 (2.5)	1.7 (2.2)	0.31	0.16
Mental disorders, %	4.5	3.9	4.5	2.8	5.3	5.6	8.1	3.4	3.2	3.3	4.2	0.08	0.03
Anxiety, %	12.6	10.4	12.5	13.5	15.7	16.3	18.8	10.9	15.0	11.9	14.6	0.09	0.03
No. outpatient visits, mean (SD)	2.5 (3.5)	2.5 (3.3)	2.1 (3.2)	1.4 (3.0)	2.9 (3.9)	3.1 (4.0)	3.0 (4.0)	2.3 (3.0)	2.1 (3.3)	2.0 (3.3)	1.5 (2.9)	0.22	0.10
No. inpatient/ED visits, mean (SD)	0.6 (1.1)	0.6 (1.0)	0.5 (1.0)	0.3 (1.0)	0.6 (1.4)	0.6 (1.2)	0.6 (1.2)	0.5 (1.0)	0.5 (1.0)	0.5 (1.1)	0.4 (0.9)	0.14	0.06
No. benzodiazepines or Z-hypnotics, mean (SD)	0.5 (3.7)	0.4 (3.4)	0.4 (3.4)	0.1 (1.2)	0.7 (1.3)	0.8 (4.9)	0.8 (4.9)	0.5 (3.4)	0.1 (2.4)	0.2 (1.8)	0.1 (0.6)	0.11	0.07
No. NSAIDs, mean (SD)	0.6 (1.4)	0.6 (1.4)	0.5 (1.3)	0.1 (0.5)	0.7 (1.5)	0.9 (1.7)	0.8 (1.7)	0.6 (1.3)	0.3 (0.9)	0.3 (0.9)	0.1 (0.4)	0.31	0.18
No. of antidepressants, mean (SD)	1.1 (2.5)	1.1 (3.4)	0.9 (2.3)	0.3 (0.9)	1.4 (2.7)	1.9 (3.3)	2.0 (3.3)	1.0 (2.2)	0.7 (1.9)	0.6 (1.6)	0.4 (0.8)	0.32	0.13
No. muscle relaxants, mean (SD)	0.3 (1.0)	0.2 (0.7)	0.2 (0.7)	0.2 (0.5)	0.5 (1.4)	0.8 (1.9)	0.8 (1.9)	0.2 (0.6)	0.2 (0.6)	0.2 (0.6)	0.2 (0.4)	0.19	0.06
No. other prescription fills, mean (SD)	16.0 (16.7)	16.0 (15.1)	11.4 (15.4)	3.9 (6.5)	21.1 (17.2)	24.4 (20.5)	21.6 (21.2)	14.5 (15.4)	7.6 (12.2)	6.7 (9.3)	3.7 (5.9)	0.72	0.40
County-level factors
No. hospitalsc, mean (SD)	2.6 (3.4)	2.6 (3.4)	2.7 (3.3)	2.5 (3.3)	2.6 (3.2)	2.6 (3.7)	2.7 (3.2)	2.5 (3.3)	2.6 (3.0)	2.7 (3.0)	2.6 (3.4)	0.03	0.03
No. physiciansc, mean (SD)	70.3 (30.9)	70.8 (31.0)	69.1 (30.2)	72.4 (28.9)	70.8 (31.5)	70.2 (31.5)	69.8 (30.6)	71.0 (30.9)	69.3 (30.2)	69.1 (29.8)	70.9 (30.6)	0.04	0.01
No. hospitals with pain management programc, mean (SD)	0.8 (1.4)	0.8 (1.5)	0.9 (1.4)	0.8 (1.4)	0.8 (1.4)	0.8 (1.4)	0.9 (1.4)	0.8 (1.3)	0.9 (1.5)	0.9 (1.3)	0.8 (1.1)	0.04	0.04
No. physical medicine/rehabilitation centersc, mean (SD)	0.4 (0.6)	0.4 (0.6)	0.4 (0.6)	0.4 (0.7)	0.4 (0.6)	0.4 (0.6)	0.4 (0.7)	0.4 (0.6)	0.4 (0.7)	0.4 (0.6)	0.4 (0.6)	0.03	0.03
Resided in metropolitan counties, %	72.4	72.8	71.4	75.9	73.2	72.0	67.0	74.6	72.2	70.0	78.0	0.08	0.01
Median household incomed, mean (SD)	51 (14)	51 (14)	50 (13)	53 (14)	52 (14)	51 (14)	50 (14)	52 (14)	50 (13)	50 (13)	52 (13)	0.10	0.01
% unemployment, mean (SD)	5.7 (1.7)	5.7 (1.7)	5.7 (1.7)	5.6 (1.6)	5.7 (1.8)	5.7 (1.8)	5.7 (1.7)	5.7 (1.9)	5.7 (1.7)	5.7 (1.6)	5.6 (1.5)	0.04	0.03

Abbreviations: ED, emergency department; GABA, gabapentinoid; IPTW, inverse probability of treatment weighting; LIS, low-income subsidy; MME, morphine milligram equivalent; No., number of; NSAID, nonsteroidal anti-inflammatory drug; OPI, opioid; SD, standard deviation; SDD, standardized daily dose; SMD: standardized mean difference.

^a.Trajectory groups: A:OPI-only early discontinuers (40.6% of the cohort); B: Consistent low-dose OPI-only users (MME ≤30; 16.6%); C: Consistent high-dose OPI-only users (MME>120; 1.8%); D: GABA-only early discontinuers (12.5%); E: Consistent low-dose GABA-only users (SDD <2; 11.0%); F: Consistent high-dose GABA-only users (SDD ≥3.5; 3.1%); G: Early discontinuation of OPIs and consistent low-dose GABA users (SDD ≤1; 6.9%); H: Consistent low-dose OPI-GABA users (MME <40 and SDD <1.5; 3.4%); I: Consistent low-dose OPI and high-dose GABA users (MME <30 and SDD ≥3; 3.2%); J: Consistent high-dose OPI and moderate-dose GABA users (MME >120 and 1.5< SDD ≤3; 0.9%). Low-, moderate-, and high-dose opioid use was defined as an average daily dosage of <50 MME, 50–90 MME, and >90 MME, respectively. For GABA use, an average daily SDD of <2 (i.e., gabapentin <600 mg or pregabalin <300 mg), 2–3 (i.e., 600≤ gabapentin <900 mg or 300≤ pregabalin <450 mg), and >3 (i.e., gabapentin ≥900 mg or pregabalin ≥450 mg) were considered as low-, moderate-, and high-dose use, respectively.

^bAverage SMD of 45 SMDs from group comparisons (the number of 2-combinations from given 10 elements: $C_2^{10}=45$; e.g., group A vs B, group A vs C, group A vs D). The maximum and minimum SMD were presented in eTable 3.

^cPer 10,000 population

^dAnnual median household income was represented in units of thousands ($)