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www.worldcancercongress.org
Disclosure of Interest: None Declared Abstract code:
Green Tea Consumption Is Associated with a Reduced Risk of Adult Leukaemia
Authors: Ping Liu, C D’Arcy J Holman, Jie Jin, Min Zhang
School of Population Health, The University of Western Australia
332
Oolong tea 8-20%
Black tea 3-10%
Green tea 30-42%
China, Japan, Africa & Middle East
≈ 20%
Southern China & Taiwan ≈ 2%
Western countries ≈ 78%
Tealeaves (Camellia sinensis)
Processing
Semi-fermented
Tea Type (Catechins, % dry weight)
BACKGROUND Tea
Ping Liu Melbourne, 5 December 2014
Reference: Graham HN. Green tea composition, consumption, and polyphenol chemistry. Prev Med 1992;21:334-50.
Where consumed
Unfermented
Fermented
% tea products worldwide
BACKGROUND & AIMS Epidemiologic studies on tea consumption and leukaemia risk
Ping Liu Melbourne, 5 December 2014
Study ID Study Design Population Participants OR/RR (95%CI)
Li 2006
Hospital-based case-control American 111 AML cases
439 controls Males 0.3 (0.1-0.8)
Females 0.5 (0.2-1.1)
Ma 2010 Cohort American 338 AML cases
491,163 cohorts 0.9 (0.6-1.2)
Kabat 2013 Cohort American 178 CML cases
493,188 cohorts 1.0 (0.7–1.4)
Zhang 2008
Hospital-based case-control Chinese 107 leukaemia cases
110 controls 0.4 (0.2-0.9)
Kuo 2009
Population-based case-control Taiwanese
252 leukaemia cases (159 children/93 adults)
637 controls
Adults 0.5 (0.2-0.9) Children 0.6 (0.2-1.8)
METHODS Study sites
Ping Liu Melbourne, 5 December 2014
Hangzhou
Shenyang
METHODS Participants Ø 493 incident cases: Diagnosed as de-novo adult leukaemia Ø 493 hospital-based controls: Free of caners at the time of recruitment Recruited from outpatients Matching cases’ gender, age, and study site
Ø Face-to-face interview
Ø Types of tea
Ø Duration of consumption
Ø Frequency of consumption
Ø Amount consumed
Ping Liu Melbourne, 5 December 2014
Tea consumption ascertainment
METHODS Other information collected Ø Demographics
Ø Lifestyle: smoking, alcohol drinking and physical activity
Ø Foods consumption: 103−item Food Frequency Questionnaire
Ø Family history of cancer
Ø Conditional logistic regression: ORs (95% CIs)
Ø Adjustments: potential confounders (demographic, lifestyle and dietary factors)
Ping Liu Melbourne, 5 December 2014
Statistical analysis
RESULTS Selected characteristics of participants
Ping Liu Melbourne, 5 December 2014
Characteristics Cases (n=493) Controls (n=493) Age at interview (yrs) 45.2±15.3 45.1±15.1 Male 289 (58.6) 289 (58.6) Residential location (Rural) 106 (21.5) 87 (17.6) Education (Tertiary)* 87 (17.6) 204 (41.4) Body mass index (≥25 kg/m²) 77 (15.6) 99 (20.1) Physical activity (MET hrs/wk) 83.7±87.6 76.1±74.1 Cigarette smoking* 178 (36.1) 149 (30.2) Alcohol drinking 281 (57.0) 274 (55.6) Coffee consumption* 81 (16.4) 124 (25.2) Vegetables intake (g/d)* 239.8±169.6 282.2±158.8 Fruits intake (g/d)* 109.9±115.6 178.6±166.9 Energy intake (kcal/d)* 2909.5±1251.5 2753.4±918.8
Cancer history in first degree relatives 49 (9.9) 49 (9.9)
* p<0.05. Categorical variables expressed as n(%); Continuous variables: mean ± SD
RESULTS Tea consumption between cases and controls
Ping Liu Melbourne, 5 December 2014
Cases (n=493,%) Controls (n=493,%)
RESULTS Adjusted ORs and 95% CIs for green tea consumption
Ping Liu Melbourne, 5 December 2014
0
0.2
0.4
0.6
0.8
1
Adj
uste
d O
R
Non-tea drinkers
Yes
All (n=806)
Men (n=471)
Women (n=335)
Yes Yes Non-tea drinkers
Non-tea drinkers
RESULTS Adjusted ORs and 95% CIs for duration of drinking (yrs)
Ping Liu Melbourne, 5 December 2014
Adj
uste
d O
R
All (n=804)
Men (n=469)
Women (n=335)
P (trend)=0.03 P (trend)<0.001 P (trend)<0.001
0
0.2
0.4
0.6
0.8
1
0 <15 >15−<30 ≥30 0 <15 >15−<30 ≥30 0 <15 >15−<30 ≥30
P (trend)<0.001
RESULTS Adjusted ORs and 95% CIs for No. of cups daily
Ping Liu Melbourne, 5 December 2014
Adj
uste
d O
R
All (n=806)
Men (n=471)
Women (n=335)
0
0.2
0.4
0.6
0.8
1
0 <1 1 ≥2 0 <1 1 ≥2 0 <1 1 ≥2 P (trend)<0.001 P (trend)=0.001
RESULTS Adjusted ORs and 95% CIs for dried tealeaves (kg/yr)
Ping Liu Melbourne, 5 December 2014
Adj
uste
d O
R
All (n=804)
Men (n=469)
Women (n=335)
0
0.2
0.4
0.6
0.8
1
0 ≤0.5 >0.5−≤1 >1 0 ≤0.5 >0.5−≤1 >1 0 ≤0.5 >0.5−≤1 >1
P (trend)<0.001 P (trend)<0.001 P (trend)=0.02
RESULTS Subgroup analysis
Ø Significant inverse dose-response relationship between green tea consumption and risk of AML was observed across all the measures.
Ø Could not analyse the associations on ALL, CML and CLL, due to small number of patients.
Ping Liu Melbourne, 5 December 2014
DISCUSSION Potential Bias
Ping Liu Melbourne, 5 December 2014
Bias?
Recall bias?
Influence by mass media?
Influence by disease status?
Hospital-based case-control
design
Reference: Li L, Zhang M, Holman D. Population versus hospital controls for case-control studies on cancers in Chinese hospitals. BMC Med Res Methodol 2011;11:167.
DISCUSSION Strengths
Ø Multi-centre study Ø Moderate sample size Ø Face-to-face interview Ø Validated questionnaire Ø High response (98% in cases vs. 92% in controls)
Ping Liu Melbourne, 5 December 2014
CONCLUSIONS
Ø Regular daily consumption of green tea can
protect against adult leukaemia.
Ø Green tea drinking, a modifiable dietary preventive
factor, may shed ‘green light’ in the primary
prevention of adult leukaemia.
Ping Liu Melbourne, 5 December 2014
ACKNOWLEDGEMENTS
¡ The authors acknowledge with gratitude the participation of participants.
¡ The authors are grateful for the collaboration received from three participating hospitals and their staff for their kind assistance in fieldwork.
¡ The work was supported by the National Health and Medical Research Council (Australia) Project Grant (572542).
¡ The presenter is supported by UWA Scholarships for International Research Fees, University Postgraduate Award for International Student, and Safety-Net Top-up Scholarship.
Ping Liu Melbourne, 5 December 2014
THANK YOU!
Ping Liu Melbourne, 5 December 2014