Tea Consumption and Risk of Chronic Obstructive Pulmonary Disease in Middle-Aged and Older Singaporean Adults

Figures & data

Figure 1 CONSORT flowchart of study recruitment, baseline assessment, follow-up and data analysis.

Table 1 Baseline Tea Intake and Related Characteristics of SLAS-1 and SLAS-2 Study Participants by the Presence and Absence of COPD (N=4617)

	No COPD		COPD		p
N (%) of participants	3460		1157
Respiratory symptoms
Chronic cough or phlegm	19.2	(666)	23.9	(276)	<0.001
mMRC breathlessness grade 1	9.3	(321)	10.8	(124)
Grade 2	3.7	(129)	5.5	(63)
Grade 3–4	0.5	(18)	1.0	(11)	<0.001
Symptomatic COPD	NA	NA	23.9	(276)
Tea (all types) intake
None	39.5	(1367)	45.7	(529)	<0.001
<1 cup a day	20.0	(693)	20.4	(236)
1–2 cups a day	25.1	(869)	22.9	(265)
3 or more cups a day	15.3	(531)	11.0	(127)
Western black tea
None	60.7	(2100)	67.2	(777)	<0.001
<1 cup a day	23.0	(796)	19.4	(224)
1–2 cups a day	13.4	(462)	11.2	(130)
3 or more cups a day	2.9	(102)	2.2	(26)
Chinese black or oolong tea
None	58.3	(2018)	63.1	(730)	0.004
<1 cup a day	26.1	(902)	23.5	(272)
1–2 cups a day	11.4	(393)	10.3	(119)
3 or more cups a day	4.2	(147)	3.1	(36)
Green tea
None	79.2	(2740)	84.5	(978)	<0.001
<1 cup a day	15.3	(531)	11.3	(131)
1–2 cups a day	4.2	(147)	3.4	(39)
3 or more cups a day	1.2	(42)	0.8	(9)
Sex: Male	36.8	(1274)	37.2	(430)	0.834
Female	63.2	(2186)	62.8	(727)
Age, years	65.7	±7.5	68.3	±7.9	<0.001
Ethnicity: Chinese	94.2	(3260)	95.1	(1100)	0.548
Malay	3.4	(119)	2.9	(34)
Indian	2.3	(81)	2.0	(23)
Housing type: 1–2 rooms public	12.7	(439)	19.4	(224)
3 rooms public	24.3	(840)	30.3	(350)
4–5 room and private housing	63.0	(2181)	50.4	(583)	<0.001
Smoking: Never	82.3	(2847)	73.4	(849)	0.000
Ex-smoker < 20 cigarettes per day	7.3	(252)	8.3	(96)
Ex-smoker 20+ cigarettes per day	3.7	(128)	4.9	(57)
Current smoker <20 cigarettes per day	5.4	(188)	11.2	(130)
Current smoker 20+ cigarettes per day	1.3	(45)	2.2	(25)
Alcohol daily	4.3	(144)	4.3	(50)	0.815
Physical activity: < 1× a month	3221	(1113)	36.0	(417)	<0.001
1× month to < 1× a week	53.8	(1837)	55.2	(639)
1× a week or more	14.0	(484)	8.7	(101)
BMI, kg/m^2	23.9	±3.8	23.5	±3.9	<0.001

Table 2 Cross-Sectional Analysis of Baseline Association of Tea Intake with Prevalent COPD

	Unadjusted OR (95% CI)		Adjusted OR (95% CI)
Tea (all types) intake:
None	1	Reference	1	Reference
<1 cup a day	0.88	(0.74, 1.05)	0.96	(0.80, 1.16)
1–2 cups a day	0.79	(0.66, 0.93)	0.87	(0.73, 1.04)
3 or more cups a day	0.62	(0.50, 0.77)	0.77	(0.61, 0.96)
p-trend	<0.001		0.048
Western black tea
None	1		1
<1 cup a day	0.76	(0.64, 0.90)	0.86	(0.71, 1.00)
1–2 cups a day	0.76	(0.62, 0.94)	0.84	(0.70, 1.08)
3 or more cups a day	0.69	(0.44, 1.07)	0.77	(0.49, 1.21)
p-trend	0.001		0.143
Chinese black or oolong tea
None	1		1
<1 cup a day	0.83	(0.71, 0.98)	0.92	(0.78, 1.08)
1–2 cups a day	0.84	(0.67, 1.04)	0.91	(0.72, 1.14)
3 or more cups a day	0.68	(0.47, 0.98)	0.74	(0.50, 1.09)
p-trend	0.026		0.361
Green tea
None	1		1
<1 cup a day	0.69	(0.56, 0.85)	0.81	(0.66, 1.00)
1–2 cups a day	0.74	(0.52, 1.07)	0.91	(0.63, 1.31)
3 or more cups a day	0.60	(0.29, 1.24)	0.79	(0.38, 1.66)
p-trend	0.001		0.254

Note: Adjusted for age, sex, ethnicity, housing type, smoking, alcohol, physical activity, BMI.

Table 3 Baseline Characteristics of COPD-Free SLAS Participants (N=920) by Tea (All Types) Intake Categories

	None		<1 Cup Daily		1–2 Cups Daily		≥3 Cups Daily
N of participants		371		193		220		136
Sex: Male	29.9	(111)	36.8	(71)	42.7	(94)	52.2	(71)	<0.001
Female	70.1	(260)	63.2	(122)	57.3	(126)	47.8	(65)
Age, years	65.2	7.2	64.1	6.6	64.2	6.2	64.3	6.1	0.168
Ethnicity: Chinese	96.2	(357)	94.3	(182)	94.5	(208)	97.8	(133)	0.697
Malay	1.9	(7)	2.1	(4)	2.1	(5)	0.7	(1)
Indian	1.9	(7)	3.6	(7)	3.6	(7)	1.5	(2)
Housing type: 1–2 rooms public	11.3	(42)	13.0	(25)	9.5	(21)	7.4	(10)	<0.001
3 rooms public	34.5	(128)	24.9	(48)	24.1	(53)	19.9	(27)
4–5 room and private housing	54.2	(201)	62.2	(120)	66.4	(146)	72.8	(99)
Smoking: Never	86.0	(319)	84.5	(163)	79.1	(174)	77.9	(106)	0.032
Ex-smoker < 20 cigarettes per day	4.0	(15)	7.8	(15)	6.4	(14)	8.1	(11)
Ex-smoker 20+ cigarettes per day	3.2	(12)	3.1	(6)	4.5	(10)	5.9	(8)
Current smoker <20 cigarettes per day	5.9	(22)	3.1	(6)	9.1	(20)	6.6	(9)
Current smoker 20+ cigarettes per day	0.8	(3)	1.6	(3)	0.9	(2)	1.5	(2)
Alcohol daily	2.2	(8)	2.1	(4)	2.3	(5)	5.9	(8)	0.074
Physical activity: < 1x a month	15.9	(59)	14.5	(28)	20.9	(46)	16.2	(22)	0.589
1× month to < 1× a week	62.8	(233)	62.2	(120)	56.8	(125)	54.4	(74)
1× a week or more	21.3	(79)	23.3	(45)	22.3	(49)	29.4	(40)
BMI, kg/m^2	23.9	3.7	23.8	3.7	24.1	3.5	23.4	2.9	0.392

Note: Figures shown are % (N).

Table 4 Longitudinal Analysis of Association of Baseline Tea Intake with Incident COPD Among COPD-Free SLAS-2 Participants

	Incident COPD % (N)		Unadjusted OR (95% CI)		Adjusted OR (95% CI)
Tea intake (all types)
None	19.7	(73)	1	Reference	1	Reference
<1 cup a day	21.8	(42)	1.13	(0.74, 1.74)	1.15	(0.74, 1.79)
1–2 cups a day	18.4	(41)	0.93	(0.61, 1.43)	0.95	(0.61, 1.48)
3 or more cups a day	8.1	(11)	0.36	(0.18, 0.70)	0.35	(0.17, 0.69)
p-trend	0.009		0.013		0.012
Western black tea
None	19.0	(109)	1	Reference	1	Reference
<1 cup a day	18.1	(40)	0.94	(0.63, 1.41)	0.93	(0.61, 1.41)
1 or more cups a day	14.1	(18)	0.72	(0.42, 1.23)	0.72	(0.41, 1.26)
p-trend	0.261		0.485		0.516
Chinese black or oolong tea
None	20.0	(107)	1	Reference	1	Reference
<1 cup a day	15.4	(36)	0.73	(0.48, 1.10)	0.70	(0.46, 1.08)
1 or more cups a day	16.0	(24)	0.76	(0.47, 1.24)	0.75	(0.45, 1.25)
p-trend	0.143		0.241		0.206
Green tea
None	19.9	(142)	1	Reference	1	Reference
<1 cup a day	13.3	(20)	0.62	(0.37, 1.03)	0.64	(0.38, 1.08)
1 or more cups a day	8.9	(5)	0.39	(0.15, 1.00)	0.42	(0.16, 1.10)
p-trend	0.009		0.034		0.065

Note: Adjusted for age, sex, ethnicity, housing type, smoking, alcohol, physical activity, BMI.

Figure 2 Baseline prevalence and 5-year cumulative incidence of COPD by consumption levels for all and different types of tea. Legends. Western black tea refers to tea consumed with milk and sugar. Chinese tea includes both black, oolong and green tea. Consumption levels are in 3 categories (third category: ≥1 cup/day) for specific tea types, and in 4 fours categories for all tea types (third category further divided into 1–2 cups/day and ≥3 cups/day).