Association of total bilirubin with depression risk in adults with diabetes: A cross-sectional study

Table 1 Baseline characteristics of participants, n (%)

Covariates	Diabetes mellitus (n = 4156)	Diabetic depression (n = 602)	P value
Age (yr)	61.12 ± 13.44	58.74 ± 12.63	< 0.001
Sex			< 0.001
Male	2268 (54.57)	222 (36.88)
Female	1888 (45.43)	380 (63.12)
Race/Ethnicity			< 0.001
Mexican American	713 (17.16)	110 (18.27)
Other Hispanic	436 (10.49)	86 (14.29)
Non-Hispanic white	1549 (37.27)	239 (39.70)
Non-Hispanic black	1015 (24.42)	127 (21.10)
Other races	443 (10.66)	40 (6.64)
BMI (kg/m2), mean ± SD	32.13 ± 7.23	35.07 ± 9.19	< 0.001
Ratio of family income to poverty	2.41 ± 1.55	1.57 ± 1.23	< 0.001
Education level			< 0.001
Did not graduate from high school	1261 (30.34)	264 (43.85)
Graduated from high school	995 (23.94)	132 (21.93)
College education or above	1900 (45.72)	206 (34.22)
Smoking status, ≥ 100 cigarettes during their lifetime	2026 (48.75)	355 (58.97)	< 0.001
Drinking status, ≥ 12 alcohol drinks a year	2874 (69.15)	418 (69.44)	0.889
Hypertension	2665 (64.12)	436 (72.43)	< 0.001
Laboratory metrics
Bilirubin (μmol/L)	10.93 ± 5.35	10.17 ± 5.10	0.001
Albumin (g/L)	41.35 ± 3.46	40.42 ± 3.67	< 0.001
ALT (U/L)	26.39 ± 20.96	30.28 ± 59.21	0.577
AST (U/L)	26.07 ± 15.14	29.71 ± 43.88	0.444
ALP (U/L)	75.59 ± 29.63	81.22 ± 29.41	< 0.001
BUN (mmol/L)	5.82 ± 2.94	5.69 ± 3.10	0.035
Creatinine (μmol/L)	89.69 ± 63.29	89.20 ± 70.31	0.027
GGT (U/L)	36.44 ± 44.20	45.22 ± 62.07	< 0.001
LDH (U/L)	138.58 ± 34.68	141.18 ± 37.72	0.090
Uric acid (μmol/L)	344.87 ± 93.23	340.47 ± 95.02	0.280
Cholesterol (mmol/L)	4.77 ± 1.21	4.90 ± 1.30	0.018
Triglycerides (mmol/L)	2.11 ± 1.99	2.33 ± 2.00	0.009

BMI: Body mass index; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; ALP: Alkaline phosphatase; BUN: Blood urea nitrogen; GGT: Gamma-glutamyl transferase; LDH: Lactate dehydrogenase.

Table 2 Association between total bilirubin and diabetic depression in different models

Total bilirubin	OR	95%CI	P value
Model 11
> 10.26	Reference
≤ 10.26	1.531	1.276-1.836	< 0.001
Model 22
> 10.26	Reference
≤ 10.26	1.230	1.006-1.503	0.043
Model 33
> 10.26	Reference
≤ 10.26	1.303	1.034-1.641	0.025

¹Model 1 did not adjust for any confounding factors.

²Model 2 adjusted for sex, age, race, body mass index, education level, drinking status, income-to-poverty ratio, smoking status, hypertension, albumin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, blood urea nitrogen, creatinine, gamma-glutamyl transferase, uric acid, lactate dehydrogenase, cholesterol and triglycerides.

³Model 3 after propensity score matching.

Table 3 Characteristics of participants before and after propensity score matching analysis, n (%)

Covariates	Before propensity score		After propensity score
	≤ 10.26 (n = 2822)	> 10.26 (n = 1936)	≤ 10.26 (n = 1583)	> 10.26 (n = 1583)
Age (yr)	60.07 ± 13.33	61.91 ± 13.33a	61.59 ± 13.40	61.96 ± 12.51
Sex
Male	1241 (43.98)	1249 (64.51)	932 (58.88)	926 (58.50)
Female	1581 (56.02)	687 (35.49)	651 (41.12)	657 (41.50)
Race/Ethnicity
Mexican American	471 (16.69)	352 (18.18)	271 (17.12)	301 (19.01)
Other Hispanic	318 (11.27)	204 (10.54)	155 (9.79)	186 (11.75)
Non-Hispanic white	967 (34.27)	821 (42.41)	673 (42.51)	537 (33.92)
Non-Hispanic black	757 (26.82)	385 (19.89)	331 (20.91)	399 (25.21)
Other races	309 (10.95)	174 (8.99)	153 (9.67)	160 (10.11)
BMI (kg/m2), mean ± SD	33.14 ± 7.94	31.57 ± 6.89a	31.89 ± 7.10	31.94 ± 7.18
Ratio of family income to poverty	2.22 ± 1.50	2.43 ± 1.58a	2.35 ± 1.56	2.35 ± 1.54
Education level
Did not graduate from high school	879 (31.15)	646 (33.37)	517 (32.66)	524 (33.10)
Graduated from high school	665 (23.56)	462 (23.86)	375 (23.69)	374 (23.63)
College education or above	1278 (45.29)	828 (42.77)	691 (43.65)	685 (43.27)
Smoking status
≥ 100 cigarettes during their lifetime	1429 (50.64)	952 (49.17)	796 (50.28)	797 (50.35)
Drinking status
≥ 12 alcohol drinks a year	1961 (69.49)	1331 (68.75)	1092 (68.98)	1094 (69.11)
Hypertension
Yes	1862 (65.98)	1239 (64.00)	1034 (65.32)	1033 (65.26)
No	960 (34.02)	697 (36.00)	549 (34.68)	550 (34.74)
Laboratory metrics
Albumin (g/L)	40.67 ± 3.40	42.05 ± 3.48a	41.69 ± 3.42	41.63 ± 3.29
ALT (U/L)	24.78 ± 16.05	29.96 ± 40.55a	26.89 ± 16.26	26.87 ± 17.81
AST (U/L)	24.60 ± 12.65	29.36 ± 29.11a	26.64 ± 12.81	26.55 ± 14.37
ALP (U/L)	77.91 ± 30.42	73.95 ± 28.36a	74.76 ± 28.15	74.39 ± 24.39
BUN (mmol/L)	5.84 ± 2.95	5.77 ± 2.96	5.86 ± 3.10	5.86 ± 2.80
Creatinine (μmol/L)	87.61 ± 58.69	92.56 ± 71.42a	92.32 ± 69.36	91.48 ± 60.95
GGT (U/L)	34.97 ± 38.25	41.31 ± 57.06a	37.02 ± 42.75	36.94 ± 40.39
LDH (U/L)	138.64 ± 32.40	139.30 ± 38.67	138.54 ± 38.29	139.35 ± 33.12
Uric acid (μmol/L)	335.54 ± 90.40	357.10 ± 96.35a	350.02 ± 96.93	351.70 ± 89.05
Cholesterol (mmol/L)	4.77 ± 1.16	4.82 ± 1.30	4.79 ± 1.28	4.77 ± 1.17
Triglycerides (mmol/L)	2.15 ± 1.51	2.11 ± 2.53a	2.11 ± 2.14	2.15 ± 1.46
Depression
Yes	410 (14.52)	193 (9.97)	200 (12.63)	169 (10.68)
No	2413 (85.48)	1743 (90.03)	1383 (87.37)	1414 (89.32)
PHQ-9 scores	4.31 ± 5.04	3.41 ± 4.47a	3.84 ± 4.78	3.54 ± 4.52

^aP < 0.05. BMI: Body mass index; ALT: Alanine aminotransferase; AST: Aspartate aminotransferase; ALP: Alkaline phosphatase; BUN: Blood urea nitrogen; GGT: Gamma-glutamyl transferase; LDH: Lactate dehydrogenase; PHQ-9: Patient Health Questionnaire-9.