Alcohol intake is associated with a decreased risk of developing primary biliary cholangitis

Table 1 Cohort characteristics of cases and controls

	Controls (n = 200)	Cases (n = 200)	Test for difference
Age, yr [mean (SD; range)]	61.5 (11.6; 29.1-95.1)	63.6 (11.6; 28.1-94.3)	P = 0.073
Sex
Male	18 (9.0)	17 (8.5)
Female	182 (91.0)	183 (91.5)	P = 0.86
Country of birth
Australia	157 (78.5)	122 (61.0)
Overseas	43 (21.5)	78 (39.0)	P < 0.001
Self-reported ethnicity
Caucasian	180 (90.0)	175 (87.5)
Asian	11 (5.5)	14 (7.0)
Other	3 (1.5)	4 (2.0)
Mixed race	1 (0.5)	0 (0)
Unspecified	5 (2.5)	7 (3.5)	P = 0.75
Education completed
Up to some secondary	3 (1.5)	18 (9.0)
Yr 10/11	33 (16.5)	56 (28.0)
Yr 12	21 (10.5)	26 (13.0)
TAFE/Trade	32 (16.0)	43 (21.5)
University	111 (55.5)	57 (28.5)	P < 0.001
Family history of PBC?
No	200 (100.0)	194 (97.0)
Yes	0 (0)	6 (3.0)
BMI (kg/m2) mean	26.8	27.1	P = 0.49

Results presented as n (%) unless otherwise specified. Differences in categorical terms between cases and controls assessed by Chi-square test. Differences in continuous terms between cases and controls assessed by t-test. Results in boldface denote statistical significance. Results in italics are P values. BMI: Body mass index; PBC: Primary biliary cholangitis; TAFE: Technical and Further Education.

Table 2 Odds ratios for primary biliary cholangitis and alcohol intake (frequency per week, drinks per session, drinker per week) for different age spans

	Controls, n (%)	Cases, n (%)	Univariable	Adjusted1	Further adjusted for current alcohol consumption
16-20 yr2
Frequency per week
Didn’t drink	70 (35.5)	91 (46.2)	1.34 (0.84, 2.13)	1.36 (0.79, 2.35)	1.32 (0.74, 2.36)
< 1 d per week	71 (36.0)	68 (34.5)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
≥ 1 d per week	56 (28.4)	38 (19.3)	0.65 (0.37, 1.15)	0.59 (0.31, 1.15)	0.71 (0.36, 1.43)
Trend			P = 0.015	P = 0.022	P = 0.088
Drinks per session
Didn’t drink	68 (35.4)	89 (46.1)	1.34 (0.81, 2.22)	1.28 (0.71, 2.31)	1.04 (0.55, 1.95)
1-2 drinks	67 (34.9)	63 (32.6)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
≥ 3 drinks	57 (29.7)	41 (21.2)	0.61 (0.33, 1.15)	0.54 (0.26, 1.09)	0.46 (0.21, 0.99)
Trend			P = 0.010	P = 0.023	P = 0.055
Drinks per week
Didn’t drink	68 (35.4)	89 (46.1)	1.50 (0.95, 2.37)	1.53 (0.89, 2.62)	1.35 (0.76, 2.41)
1-5 drinks per week	87 (45.3)	79 (40.9)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
≥ 6 drinks per week	37 (19.3)	25 (13.0)	0.67 (0.35, 1.27)	0.71 (0.35, 1.48)	0.85 (0.40, 1.82)
Trend			P = 0.014	P = 0.065	P = 0.26
21-30 yr2
Frequency per week
Didn’t drink	19 (9.9)	64 (33.5)	3.11 (1.59, 6.08)	3.11 (1.42, 6.79)	2.81 (1.26, 6.29)
< 1 day per week	65 (33.9)	69 (36.1)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
1-2 days per week	69 (35.9)	43 (22.5)	0.49 (0.27, 0.86)	0.48 (0.25, 0.92)	0.51 (0.26, 1.00)
≥ 3 days per week	39 (20.3)	15 (7.9)	0.26 (0.11, 0.57)	0.18 (0.07, 0.47)	0.22 (0.09, 0.57)
Trend			P < 0.001	P < 0.001	P < 0.001
Drinks per session
Didn’t drink	18 (9.6)	63 (33.9)	5.57 (2.76, 11.22)	4.81 (2.18, 10.65)	3.99 (1.76, 9.01)
1-2 drinks	102 (54.6)	67 (36.0)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
≥ 3 drinks	67 (35.8)	56 (30.1)	1.03 (0.61, 1.77)	0.78 (0.41, 1.46)	0.89 (0.46, 1.71)
Trend			P < 0.001	P < 0.001	P = 0.003
Drinks per week
Didn’t drink	18 (9.6)	63 (33.9)	5.05 (2.53, 10.09)	4.77 (2.16, 10.53)	3.89 (1.73, 8.76)
1-5 drinks per week	98 (52.4)	75 (40.3)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
6-10 drinks per week	47 (25.1)	37 (19.9)	0.86 (0.49, 1.53)	0.82 (0.42, 1.58)	0.84 (0.43, 1.65)
≥ 11 drinks per week	24 (12.8)	11 (5.9)	0.52 (0.23, 1.18)	0.31 (0.12, 0.83)	0.42 (0.15, 1.14)
Trend			P < 0.001	P < 0.001	P = 0.001
31-40 yr2
Frequency per week
Didn’t drink	14 (9.2)	47 (31.1)	3.60 (1.28, 10.11)	3.60 (1.10, 11.81)	3.57 (1.09, 11.72)
< 1 day per week	49 (32.2)	52 (34.4)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
1-2 days per week	53 (34.9)	35 (23.2)	0.56 (0.27, 1.18)	0.64 (0.28, 1.47)	0.69 (0.30, 1.60)
≥ 3 days per week	36 (23.7)	17 (11.3)	0.28 (0.11, 0.70)	0.29 (0.10, 0.84)	0.36 (0.12, 1.08)
Trend			P < 0.001	P < 0.001	P = 0.002
Drinks per session
Didn’t drink	13 (8.8)	46 (31.1)	5.12 (1.92, 13.67)	4.48 (1.48, 13.59)	3.94 (1.27, 12.27)
1-2 drinks	94 (64.0)	71 (48.0)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
≥ 3 drinks	40 (27.2)	31 (21.0)	0.85 (0.42, 1.73)	0.71 (0.33, 1.55)	0.81 (0.36, 1.81)
Trend			P = 0.002	P = 0.006	P = 0.034
Drinks per week
Didn’t drink	13 (8.8)	46 (31.1)	3.65 (1.34, 9.91)	3.51 (1.13, 10.93)	3.00 (0.95, 9.54)
1-5 drinks per week	78 (53.1)	72 (48.7)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
6-10 drinks per week	38 (25.9)	18 (12.2)	0.37 (0.15, 0.89)	0.38 (0.14, 1.01)	0.39 (0.15, 1.03)
≥ 11 drinks per week	18 (12.2)	12 (8.1)	0.51 (0.19, 1.38)	0.48 (0.16, 1.40)	0.66 (0.20, 2.15)
Trend			P < 0.001	P = 0.001	P = 0.008

Associations with case status assessed by conditional logistic regression, grouped on the linkage identifier for matched cases and controls.

¹Adjusted models adjusted for whether participant was born in Australia, education completed, and whether participant had ever smoked.

²Cases (and their linked controls) who had been diagnosed prior to each age span were excluded from analysis, including 1 case/control pair for 16-20 yr, 8 case/control pairs for 21-30 yr, and 47 case/control pairs for 31-40 yr.

PBC: Primary biliary cholangitis.

Table 3 Odds ratios for the association between tobacco and marijuana intake and primary biliary cholangitis development

	Controls (n = 200), n (%)	Cases (n = 200), n (%)	Univariable	Adjusted1	Adjusted2
Ever smoked tobacco prior to PBC diagnosis
No	116 (58.0)	89 (44.5)	1.00 [Reference]	1.00 [Reference]
Yes	84 (42.0)	111 (55.5)	1.73 (1.15, 2.59)	1.42 (0.88, 2.30)
			P = 0.008	P = 0.15
Age started smoking tobacco
Never smoker	115 (57.8)	88 (44.2)	1.00 [Reference]	1.00 [Reference]
10-15	19 (9.6)	24 (12.1)	1.66 (0.79, 3.47)	1.16 (0.49, 2.74)
> 15-17	30 (15.1)	35 (17.6)	1.59 (0.87, 2.91)	1.15 (0.57, 2.31)
> 17-19	19 (9.6)	26 (13.1)	1.66 (0.87, 3.16)	1.72 (0.79, 3.73)
> 19-38	16 (8.0)	26 (13.1)	2.23 (1.10, 4.53)	2.16 (0.97, 4.83)
Trend			P = 0.008	P = 0.022
Years smoking tobacco prior to PBC diagnosis
Never smoker	115 (57.8)	88 (44.2)	1.00 [Reference]	1.00 [Reference]
0-10	28 (14.1)	23 (11.6)	1.15 (0.63, 2.09)	1.07 (0.54, 2.13)
> 10-20	26 (13.1)	32 (16.1)	1.63 (0.89, 3.00)	1.18 (0.58, 2.38)
> 20-35	22 (11.1)	41 (20.6)	2.46 (1.33, 4.55)	2.27 (1.12, 4.62)
> 35-59.9	8 (4.0)	15 (7.5)	2.47 (1.01, 6.06)	1.90 (0.68, 5.30)
Trend			P = 0.001	P = 0.018
Ever smoked marijuana prior to PBC diagnosis
No	184 (92.0)	179 (89.5)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
Yes	16 (8.0)	21 (10.5)	1.36 (0.68, 2.71)	1.45 (0.66, 3.20)	1.27 (0.56, 2.87)
			P = 0.39	P = 0.36	P = 0.56
Marijuana smoking status (constrained to starting smoking marijuana prior to PBC diagnosis)
Never smoker	184 (92.0)	179 (89.5)	1.00 [Reference]	1.00 [Reference]	1.00 [Reference]
Ex-smoker	16 (8.0)	19 (9.5)	1.21 (0.60, 2.46)	1.23 (0.55, 2.79)	1.10 (0.48, 2.55)
Current smoker	0 (0)	2 (1.0)	-	-	-

Associations with case status assessed by conditional logistic regression, grouped on the linkage identifier for matched cases and controls.

¹Adjusted models adjusted for whether participant was born in Australia and education completed.

²Adjusted models adjusted for whether participant was born in Australia, education completed, and whether participant had ever smoked tobacco.

PBC: Primary biliary cholangitis.