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Drinking and Smoking and Colorectal Cancer - A Population-Based Case-Control Study among NL Residents, 1999-2003

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Drinking and Smoking and Colorectal Cancer - A Population-Based Case-Control Study among NL Residents, 1999-2003. PhD student: Jinhui Zhao Supervisor: Peizhong Peter Wang Committee: Roy West and Sharon Buehler The Annual Colorectal Meeting, June 16-17, 2008, St John’s, NL. Background.

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Drinking and Smoking and Colorectal Cancer - A Population-Based Case-Control Study among NL Residents, 1999-2003

PhD student: Jinhui Zhao

Supervisor: Peizhong Peter Wang

Committee: Roy West and Sharon Buehler

The Annual Colorectal Meeting, June 16-17, 2008, St John’s, NL

background
Background
  • Studies on the effects of drinking and smoking on colorectal cancer (CRC) have been inconclusive
  • One study on smoking and CRC conducted in Montreal did not provide evidence (1995)
  • One study on drinking and CRC in Montreal men showed OR=2.3 (95% CI:1.4-3.7) of distal colon cancer and OR=1.6 (95% CI: 1.0-2.6) for daily drinkers vs non-drinkers (2002)
  • Drinking beer showed stronger effect on proximal, distal and rectum cancer than wine and spirits

ACM, June 16-17, 2008, St. John\'s NL

research questions
Research questions
  • Incidence rate is high in eastern provinces
  • Age-standardized rate is highest (83/100,000) in NL males and second highest (51) in NL females
  • Highest rate of heavy drinkers is 3 territories, NL and NS
  • Smoking rate in BC, AB, NL and NS exceeded the national average

ACM, June 16-17, 2008, St. John\'s NL

research questions4
Research questions
  • Drinking and smoking are potential risk factors of CRC?
  • Subtypes risk of CRC may vary
  • Effects may vary based on types of beverages and tobaccos (differential brands of beverages and tobaccos
  • CRC cluster may exist, but has not been taken into account in studies and statistical analyses

ACM, June 16-17, 2008, St. John\'s NL

objective of study
Objective of study
  • To investigate effects of drinking and smoking on CRC and its subsites
  • To investigate effects of drinking beer, wine and spirits on CRC and its subsites
  • To investigate effects of smoking cigarette, cigar and pipe on CRC and its subsites
  • Evaluate validity of reliability of self-reported lifetime drinking and smoking
  • Investigate non-participation bias of CRC cases

ACM, June 16-17, 2008, St. John\'s NL

research methods designs
Research methods-designs
  • Case-control study for effect of drinking and smoking on CRC
  • Comparison of characteristics of CRC participants with non-participants
  • Annul ethanol litres and annual cigarettes and cigarette packs per control compared to 1996 and 2001 alcohol and tobacco sale data by Statistics Canada for validity
  • Cronbach’s alpha for internal reliability

ACM, June 16-17, 2008, St. John\'s NL

research methods analyses
Research methods-analyses
  • Binary multilevel logistic model for all CRC cases to controls
  • Multinomial multilevel logistic model for colon, rectum cancer cases to controls
  • Multinomial multilevel logistic model for survival, died cases to controls
  • Multinomial multilevel logistic model for CRC at stage I-II, III-IV to controls

ACM, June 16-17, 2008, St. John\'s NL

what do we find non response bias
What do we find?-non-response bias
  • 59.94% eligible CRC cases and 44.76% eligible controls participated in the study
  • Cases aged 20-54 tended to over-represent
  • Cases aged 65 years old and over tended to under-represent in the participating sample.
  • Participating rate tended to decrease with an increase in TNM stages
  • The most serious cases tended to under-represent in the participating sample
  • The deceased tended to be included in the study

ACM, June 16-17, 2008, St. John\'s NL

what do we find reliable self report
What do we find?-reliable self-report
  • Self-reported substance uses are reliable:
  • Reliability of self-reported drinking:
  • Internal reliability of all constructed alcohol-items is high, with
  • Cronbach α = 0.9144 (70+ is acceptable)
  • Reliability of self-reported smoking
  • Internal reliability of all constructed tobacco-items is high, with
  • Cronbach α = 0.8966 (70+ is acceptable)

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report
What do we find?-valid self-report
  • What did CRC cases and controls drink?

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report11
What do we find?- valid self-report
  • What did a Canadian drink?

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report12
What do we find?-valid self-report
  • How much did a CRC case and control drank per year?

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report13
What do we find?-valid self-report
  • How much did a Canadian drink?

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report14
What do we find?-valid self-report
  • What and how much did a CRC case and control smoke?

ACM, June 16-17, 2008, St. John\'s NL

what do we find valid self report15
What do we find?-valid self-report
  • How much did a Canadian smoke?

ACM, June 16-17, 2008, St. John\'s NL

what do we find effects of drinking
What do we find?-effects of drinking
  • Drinking shows weak protective effect on CRC risk
  • 42% lower risk of CRC for drinking 1-19 years vs never drinker (OR: 0.58, 95% CI: 0.37-0.91)
  • 43% lower risk of CRC for drinking beer 1-19 yrs vs no (OR: 0.57, 95% CI: 0.36-0.92)
  • 1-2 drinks of beer decreased by 33% CRC risk compared to no (OR: 0.67, 95% CI: 0.47-0.96)
  • 42% lower risk of CRC for drinking liquor 1-19 years vs no (OR: 0.53, 95% CI: 0.35-0.80)

ACM, June 16-17, 2008, St. John\'s NL

what do we find beer liquor
What do we find?-beer & liquor
  • Drinking shows weak protective effect on risk of rectum cancer but not colon cancer
  • Drinking shows weak protective effect on risk of died CRC, but not survival CRC
  • Drinking shows weak protective effect on risk of CRC at stage III-IV, but not CRC at stage I-II

ACM, June 16-17, 2008, St. John\'s NL

what do we find effects of smoking
What do we find?-effects of smoking
  • Cigarette smoking increased CRC risk (OR & 95% CI)

ACM, June 16-17, 2008, St. John\'s NL

what do we find effects of smoking19
What do we find?- effects of smoking
  • CRC risk increased with smoking cigarette years, number of cigarettes per day, cigarette pack years, and years since cigarette commencing
  • CRC risk decreased with years of abstention from smoking cigarettes
  • CRC risk associated with age of initiation of smoking greater than 16 years old

ACM, June 16-17, 2008, St. John\'s NL

what do we find effects of smoking20
What do we find?-effects of smoking
  • Smoking increased CRC risk of males, but females
  • Smoking increased CRC risk of drinkers, but not non-drinkers
  • Smoking shows stronger effect on rectum than colon cancer
  • Smoking shows stronger effect on died CRC than survival CRC
  • Smoking shows stronger effect on CRC at stage III-IV than CRC at stage I-II

ACM, June 16-17, 2008, St. John\'s NL

in summary
In summary
  • Non-participation bias: low participation rate among eligible cases & controls might bias the estimates to be generalized to wide population, but it seems unlikely that the bias would be substantial enough to account for the main results
  • Validity and reliability of self-reported drinking and smoking: accurate and reliable

ACM, June 16-17, 2008, St. John\'s NL

in summary22
In summary
  • Drinking shows weak protective effect on CRC.
  • Smoking cigarettes significantly increased CRC risk
  • CRC risk increased with smoking cigarette years, smoking pack years, daily number of cigarettes, years since cigarettes smoking commencing
  • Smoking increased CRC risk among males and drinkers
  • Smoking tended to be stronger effect on rectum cancer than colon, died CRC than survival, and CRC at stage III-IV than I-II

ACM, June 16-17, 2008, St. John\'s NL

what shall we do next
What shall we do next?
  • Regarding the study:
  • Further studies to evaluate the effects of drinking on CRC among Canadians
  • Expand studies of smoking and CRC in other provinces
  • Regarding our study:
  • Complete my thesis
  • Complete 3-4 papers for publication
  • Complete one report and submit to NL government and other provinces to share our results
  • Incorporate alcohol & tobacco sale data into multilevel analysis which will help us to explain effects of alcohol & tobacco use on CRC in Canada

ACM, June 16-17, 2008, St. John\'s NL

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