H/A: Hyperlipidemia (2009)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To investigate the relationship among habitual exercise, diet and the presence of metabolic abnormalities, such as body fat redistribution, dyslipidemia and insulin resistance in HIV-infected subjects.

Inclusion Criteria:
  • Age more than 16 years
  • Documented HIV infection
  • More than six months cumulative exposure to any antiretroviral regimen.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

The study evaluated 120 HIV-infected subjects during a single outpatient visit to the General Clinical Research Center.

Design

Cross-sectional study. 

Statistical Analysis

  • Kruskal-Wallis tests followed by post hoc Mann Whitney analysis for comparison of continuous variables
  • Chi-squared tests followed by post hoc Fisher's exact analysis used for categorical variables
  • Compared all subgroups using independent Student's T-test or Mann-Whitney tests for continuous variables and chi-squared tests for categorical variables
  • Bivariate and multivariate regression analysis models
  • Bonferroni's correction was used to adjust for multiple comparisons.
Data Collection Summary:

Timing of Measurements

One-time measurement made during single outpatient visit.

Dependent Variables

  • Laboratory data: Fasting serum glucose level, insulin level, lipid profile, insulin resistance
  • Body composition measured using DEXA and single slice CT scans at L4 level.

Independent Variables

  • Food intake measured through validated self-administered food frequency questionnaire
  • Habitual exercise evaluated using three multiple-choice questions regarding type and intensity of exercise.

Control Variables

  • Age
  • Sex
  • Total amount of tobacco use
  • Amount of current alcohol use
  • Energy intake
  • CD4 count
  • Duration of exposure to HIV treatment
  • BMI
  • Waist to hip ratio
  • Body composition.
Description of Actual Data Sample:
  • Initial N: 120 subjects
  • Attrition (final N): 120 subjects, 89% male
  • Age: Mean age, 43.7±8.0 years
  • Ethnicity: 104 Caucasian (76%), nine African Americans, seven Hispanic
  • Location: Boston, MA.
Summary of Results:

Other Findings

51 subjects (43%) did not have any evidence of fat redistribution, whereas 17 subjects (14%) had regional fat accumulation, 23 (19%) had peripheral fat wasting and 29 (24%) had a mixed fat redistribution profile.

Total and aerobic exercise were significantly and negatively associated with fasting plasma triglyceride levels in the entire sample (P=0.004) and in the fat redistribution group (P=0.008).

Inverse associations between total or aerobic exercise and insulin resistance were suggestive but did not achieve statistical significance.

Subjects in each group reported a higher dietary fat intake than is recommended for the general population but a relatively lower carbohydrate percentage intake.

Diastolic blood pressure was significantly and inversely associated with supplemental or total but not habitual dietary intake of vitamin E (P=0.01).

We found no significant relationships between any dietary components and fasting triglycerides, LDL, HDL or total cholesterol levels.

There were no significant interactions between vitamin E and exercise, dietary fiber and exercise or P:S fat ratio and exercise in relation to metabolic parameters. 

Author Conclusion:

In conclusion, we found that exercise is independently and inversely associated with fasting triglyceride levels and possibly insulin resistance, whereas vitamin E intake is inversely associated with diastolic blood pressure in HIV-positive subjects. The cross-sectional nature of this study limits determinations of temporality or causality. Therefore, future cohort and interventional studies to confirm this data and to assess the potential therapeutic efficacy of exercise and diet in HIV-associated metabolic syndrome are needed.

Funding Source:
Reviewer Comments:

Authors note small sample sizes in some of the subgroups, as well as the fact that the findings may not be directly relevant to all ethnic groups. 

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) N/A
  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) N/A
 
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? ???
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 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? Yes
  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.) Yes
  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? 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.) Yes
  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? N/A
  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? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  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? N/A
  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? No
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