NC: Motivational Interviewing (2008)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
  • The study hypothesis was that motivational interviewing is more effective in lowering serum cholesterol levels in patients with hyperlipidemia than standard dietary advice
  • Objectives were to compare the effectiveness of two methods of dietary education in increasing motivation for change (Stage of Change), increasing knowledge of recommended diet, achieving reductions in dietary fat intake in line with current guidelines, improving lipid profiles, and reducing weight where appropriate.
Inclusion Criteria:
  • Patients with hyperlipidaemia (total cholesterol level over 5.2mmol per L with or without raised serum triacyglycerol levels, over 2.0mmol per L)
  • Referred to the hospital-based dietetic department for lipid-lowering dietary advice between April 1995 and August 1996.
Exclusion Criteria:

Patients were excluded if they had any of the following conditions: Thyroid disorders, hepatic disease, renal disease, diabetes mellitus, pregnancy or if they were taking lipid-loweing medication or medications know to affect lipid levels or had a myocardial infarction within the previous three months.

Description of Study Protocol:
  • Recruitment: Patients referred by their physician for lipid-lowering dietary advice between April 1995 and August 1996. 
  • Design: 121 patients with hyperlipidaemia were randomized to receive either standard or motivational dietary interventions for a period of three months.
  • Intervention: Patients randomized to the standard intervention received standard lipid-loweing dietary advice and given a lipid-lowering diet sheet. Motivational interviewing was used on the intervention group.
  • Statistical analysis: Data were collated and analyzed using SPSS, P-values less than 0.05 were considered statistically significant.
Data Collection Summary:

Timing of Measurements

  • Baseline
  • Six weeks
  • Three months.

Dependent Variables

  • Blood lipid values including total serum cholesterol, ratio of total cholesterol to HDL-cholesterol and levels of serum triacylglycerol
  • Nutrient intakes were assessed using a seven-day food record and computerized nutrition software
  • Other data included qualitative data on foods eaten, dietary knowledge and stage of change, exercise habits, smoking, alcohol intake and weight or body mass index (BMI).

Independent Variables

  • Standard intervention for lipid-lowering
  • Motivational Interviewing technique.
Description of Actual Data Sample:
  • Initial N: 121
  • Attrition (final N): 24 subjects did not complete the study; 13 were lost to follow-up; 11 were excluded because they started lipid-lowing medication (N=97; 20% attrition)
  • Age: No statistically significant differences
  • Other relevant demographics: Within the motivational intervention group, 23 were male (49%) and 24 were female (51%). Within the standard intervention group, 26 were male (52%) and 24 were female (48%).
  • Anthropometrics: No statistically significant differences in BMI or lipid levels between the groups at baseline
  • Location: Southampton General Hospital, Southampton, UK.
Summary of Results:

Changes in Clinical Outcomes
[Values in parentheses are 95% confidence level. Student's T-test was used for comparison between intervention groups.]

  Motivational Group Standard Group Difference Between Intervention Groups P- Value
Baseline Mean Change from Baseline Baseline Mean Change from Baseline
(-0.65, -0.25)

(-0.60, -0.20)

(-0.26, 0.25)
Total Cholesterol (mmol/L)
(-0.20, 0.11)
(-0.25, 0.13)
(-0.29, 0.25)
HDL Cholesterol (mmol/L)
(-0.02, 0.06)
(-0.01, 0.00)
(-0.07, 0.05)
Total- to HDL-Cholesterol Ratio
(-0.48, 0.06)
(-0.49, -0.02)
(-0.31, 0.40)
Triacyglycerols (mmol/L)
(-0.21, 0.17)
(-0.29, 0.05)
(-0.15, 0.35)

Other Findings

Results of interview coding demonstrated that there were significant differences between the techniques used in both interventions. The motivational interviews contained significantly more reflecting, exploring and non-judgmental giving of information, while the standard interviews contained significantly more advice and patient resistance. The motivational interview was significantly longer than the standard interview 1, 42 minutes vs. 25 minutes; (P,0.001); interview 3, 15 minutes vs.13 minutes (P=0.05).

Author Conclusion:
  • The results suggest that dietary counseling did affect dietary knowledge and behavior and led to a reduction in body weight, but not serum cholesterol
  • Motivational interviewing was no more effective than standard interviewing.
Funding Source:
Government: South and West Regional Health Authority
Reviewer Comments:
  • All treatments, the standard and the motivational interviews, were conducted by the same dietitian
  • The study took place over a 17-month period of time: The length required to recruit 196 potential subjects.
Quality 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 dieteticspractice? 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? Yes
  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) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? N/A
  3.5. If case control 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.) 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? Yes
  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? Yes
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  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? Yes
  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? N/A
  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)? N/A
  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