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Citation:

 Järvinen R, Knekt P, Hakulinen T, Rissanen H, Heliövaara M. Dietary fat, cholesterol and colorectal cancer in a prospective study. Br J Cancer. 2001;85(3):357-61.


PubMed ID: 11487265
Study Design:
Prospective cohort design
Class:
B - Click here for explanation of classification scheme.
POSITIVE: See Research Design and Implementation Criteria Checklist below.
Research Purpose:

The purpose of this study was to investigate the relationships between consumption of dietary fat, cholesterol, protein, meat and eggs and incidence of colorectal cancer.

Inclusion Criteria:

The subjects of this study were men and women who participated in a population-based health examination survey carried out in Finland during 1966-1972.

Exclusion Criteria:

None noted.

Description of Study Protocol:

Recruitment

 A mailed invitation was sent to subjects who had participated in the population-based health examination survey carried out in Finland during 1966-1972.

Design

 Dietary and questionnaire data was compared to the incidence of colorectal cancer. 

Statistical Analysis

 The associations between dietary variables and the incidence of colon and rectal cancers were investigated utilizing the Cox proportional hazards model. The relative risks (RR) and 95% confidence intervals (CI) were calculated for different quartiles of food and nutrient intakes, using the lowest quartile as the reference category.

Data Collection Summary:

Timing of Measurements

 Baseline (1967); end of ascertainment of new cancer cases (1999)

Dependent Variables

  • Cancer incidence: ascertained through the national Finnish Cancer Registry

Independent Variables

  •  Diet: interview carried out by trained interviewers who used a structured questionnaire to gather data. The average consumption of different food items and nutrients was computed using a software package specifically designed for this study.

Control Variables

  •  Sociodemographic factors, smoking, medical history, use of drugs and food supplements was gathered from a self-administered mailed questionnaire.
  • Weight and height wer gathered during an examination. BMI was calculated
Description of Actual Data Sample:

 

Initial N: mailed invitation sent to 33,382 men and 29,058 women

Attrition (final N): 9959 (81.9% of men and 83.2% of women participated in the survey)

Selected baseline characteristics

Variable Colorectal Cancer (n=109) Noncases (n=9850
Age, years 49.5 39.0
Body Mass Index 25.6 24.8
Current smoking, % 31.8 35.3
Energy, kcal 2516 2595

Location: Finland

 

Summary of Results:

 Key Findings:

  • High cholesterol intake was associated with increased risk for colorectal cnacers.
  • Consumption of total fat and intake of saturated, monounsaturated, or polyunsaturated fatty acids were not significantly associated with colorectal cancer risk.
  • Nonsignificant associations were found between consumption of meat and eggs and colorectal cancer risk.
  • From 1967-1972 to 1999, 109 new colorectal cancer cases (63in colon and 46 in rectum) were ascertained.
  •  Total consumption of meat (all), red meat, or liver was not significantly associated with the incidence of colorectal cancers.
  • The RR between extreme quartiles for colorectal cancer and meat (all) and red meat were 1.52 (95% CI: 0.78, 2.96) and 1.50 (95% CI: 0.77, 2.94), respectively.
  •  Those who consumed poultry meat had an increased risk for colorectal cancers mainly due to an increase risk for colon cancer (RR = 1.93; 95% CI: 1.12-3.35).
  • Egg consumption was not significantly related to colorectal cancer risk.
Author Conclusion:

The results of this prospective study suggest that high cholesterol intake may be a risk factor for colorectal cancers, whereas no significant relationships were observed between colorectal cancer incidence and the intake of total fat, various major fatty acids, or total dietary protein.

Reviewer Comments:

Research Design and Implementation Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)
Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?
Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to nutrition or dietetics practice?
Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies)
Yes
 
Validity Questions
1. Was the research question clearly stated?
Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?
Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated?
Yes
  1.3. Were the target population and setting specified?
Yes
2. Was the selection of study subjects/patients free from bias?
Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?
Yes
  2.2. Were criteria applied equally to all study groups?
N/A
  2.3. Were health, demographics, and other characteristics of subjects described?
Yes
  2.4. Were the subjects/patients a representative sample of the relevant population?
Yes
3. Were study groups comparable?
Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)
N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?
N/A
  3.3. Were concurrent controls used? (Concurrent preferred over historical controls.)
N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?
Yes
  3.5. If case control or cross-sectional study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable. Criterion may not be applicable in some cross-sectional studies.)
N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?
N/A
4. Was method of handling withdrawals described?
Yes
  4.1. Were follow-up methods described and the same for all groups?
N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)
Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for?
Yes
  4.4. Were reasons for withdrawals similar across groups?
N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study?
N/A
5. Was blinding used to prevent introduction of bias?
Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?
N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)
N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?
Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status?
N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results?
N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?
Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied?
N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described?
N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?
Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured?
Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described?
N/A
  6.6. Were extra or unplanned treatments described?
N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?
Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient?
N/A
7. Were outcomes clearly defined and the measurements valid and reliable?
Yes
  7.1. Were primary and secondary endpoints described and relevant to the question?
Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern?
Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur?
Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?
Yes
  7.5. Was the measurement of effect at an appropriate level of precision?
Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes?
Yes
  7.7. Were the measurements conducted consistently across groups?
Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators?
Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately?
Yes
  8.2. Were correct statistical tests used and assumptions of test not violated?
Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals?
Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?
N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?
Yes
  8.6. Was clinical significance as well as statistical significance reported?
Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error?
N/A
9. Are conclusions supported by results with biases and limitations taken into consideration?
Yes
  9.1. Is there a discussion of findings?
Yes
  9.2. Are biases and study limitations identified and discussed?
Yes
10. Is bias due to study’s funding or sponsorship unlikely?
Yes
  10.1. Were sources of funding and investigators’ affiliations described?
Yes
  10.2. Was the study free from apparent conflict of interest?
Yes
 
 

Copyright American Dietetic Association (ADA).