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SCI: Lipid Abnormalities (2007)

Citation:

Janssen TW, van Oers CA, van Kamp GJ, TenVoorde BJ, van der Woude LH, Hollander AP. Coronary heart disease risk indicators, aerobic power, and physical activity in men with spinal cord injuries. Arch Phys Med Rehabil. 1997;78(7):697-705.

PubMed ID: 9228871
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  • To compare the lipid and (apo-) lipoprotein profile and blood pressure of men with long-standing spinal cord injuries (SCI) to those of an age-matched able-bodied (AB) propulation and to assess the most important determinants of this profile and blood pressure.
  • To investigate whether these men were at increased risk of CHD compared to AB men using lipid, lipoprotein, and blood pressure values
  • To assess the most important determinants of the lipid and lipoprotein profile and blood pressure among men with SCI using age, lesion level, TSI, aerobic power, behavioral factors (activity level, smoking, and drinking behavior), anthropometric actors (body mass, body mass index, and skinfolds) and family history as independent factors.
Inclusion Criteria:

Caucasian men in an age range of 19-71 years with long standing SCI (TSI range 4-33 years).

Exclusion Criteria:

Subjects without long standing SCI

Patients unable to propel a wheelchair manually

Age below 16 years.

Women

Description of Study Protocol:

Study Protocol

 Thirty-seven men (age 37.4 +/- 12.0 years) with long standing (14.7 +/- 8.6 years) SCI ranging from level C4/5 to L5 volunteered to participate.  Comparisons were made with published data from 3. 498AB men, age 20 - 59 years, from the same country.

Design

 Cross Sectional Design

Statistical Analysis

 A one-way analysis of of variance (ANOVA) was applied to study differences in subject characteristics, anthropometric factors, behavioral factors, blood pressure, and lipid and (apo-) lipoprotein profile among lesion groups.

A Tukey post hoc test was applied to indicate which groups were different.

A two-sample t  test (for equal and unequal variance) compared TC, HDL-C, TC/HDL-C, SBP, DBP, and BMI of hte men with SCI with those of the age-matched AB population.

Pearson correlation coefficients were determined for the relations among the lipid and lipoprotein profile, blood pressure, age, TSI, aerobic power, alcohol consumption, and anthropometric factors. 

Spearman correlations determiend the relations with the ordinal measures smoking behavior, family history, and lesion level.

Multiple regression analysis was performed to estimate the most important predictors of lipid and lipoprotein fractions and blood pressure.

Data Collection Summary:

 

Independent Variables

Age, lesion level, TSI, aerobic power, behavioral factors (activity level, smoking and drinking behaviors), anthropometric factors (body mass, BMI, and skinfolds) and family history.

Experimental procedure

  •  Subjects reported to the laboratory at noon so blood samples could be collected for determination of the blood lipid profile.
  • An interviewer administered questionnaire elicited behavioral factors, family history of CHD or hypertension, medication use, and health status. 

Anthropometric Factors

  • Body mass was determined with a Berkel sclae with the subjects dressed in light clothing (height was self-reported).
  • Subjects were classified as grade I obese when BMI exceeded 25 or as grade II obese when BMI exceeded 30.
  • Subcutaneous adipose tissue was estimated by the sum of 4 skinfolds, determined three times (and averaged) at triceps, biceps, subscapular, and suprailiac sites, with the subject sitting in his wheelchair.
  • Blood pressure was dermined at least 2 hours after a light lunch, followed by a graded exercise test to assess aerobic power.

Behavioral Factors

  • Activity level was defined as the number of hours of active sports participation per week. 
  • Relatively passive sports (eg shooting, chess, bridge) were not included in this activity level assessment.
  • No further distinction in type or intensity of sport participation were made
  • Subjects were classified according to their regular smoking behavior: nonsmoker (1) , light smoker (fewer than 10 cigarettes per day)(2), heavy smoker (10 or more than 10 cigarettes per day) and/or cigar/pipe smoker (3) . 
  • Alcohol consumption was defined as teh average number of alcohol-containing drinks per day.

Family History

  • Subjects were classified on basis of family history of CHD: subjects with no history (1), or with parents (2), brother/sister (3), or parents and brother/sister (4) with CHD.
  • Analogously a classification based on family history was made

Aerobic Power

  • All subjects performed a graded discontinuous maximla wheelchair exercise test in their daily-use wheelchair on a motor-driven treadmill.
  • Test was ended when subject could no longer maintain his position on the belt.
  • Expired air was collected during the exercise periods and analyzed with 30-sec samples with an Oxycon OX4. 
  • Aerobic power was defined as the highest 30-sec value found during the test.
  • For safety reasons no Vo peak was determined in the oldest subject (age 71 years)

Blood lipids and (apo-)lipoproteins

  • Subjects had been allowed to eat a light low-fat breakfast (bread and tea only).  However most subjects abstained from the breakfast.
  • TC and TG were determiend using an exzymatic colorimetric test.
  • HDL subfractions and cholesterol were determined
  • LDL-C was calculated by subtractingthe HDL-C determined by precipitation from the cholestrol in the bottom fraction.
  • ApoA-1 and apolipoprotein B-1 (apoB) were determined with immunonephelometric assays and apoA-2 was determined with a turbidimetric immunoassay using microliter plates. 
  • In one subject, the cholesterol subfractions were not determined.  

Blood Pressure

  •   Systolic (SBP) nad diastolic (DBP) finger arterial pressures were continuously recorded with a noninvasive blood pressure monitor while subjects were sitting in their wheelchair.
  • The finger arterial pressure as measured with this device has been shown to agree well with intraarterial blood pressure duing resting conditions, showing a tendency (not significant) towards overestimation (+2+/- 11mmHg) and underestimation (-3+/- 7mmHg) of DBP.
  • Average values of 3 min continuously recording were calculated.
  • Subjects were classified as hypertensive when SBP of >/= 160 mmHg or DBP or >/= 95 mmHg.

Control Variables/AB Population

  •  The lipoprotein profile (TC, HDL-C, the ratio TC/HDL-C) BMI, SBP, and DBP of men with SCI were matched with data obtained from an age-and sex-matched AB population from the same country as the subjects with SCI
Description of Actual Data Sample:

 

Initial N: Thiry-seven men with long-standing 14.7 +/- 8.6 years SCI ranging from level C4/5 to L5.

Attrition (final N): 37

Age: 19 - 71 years, median 32

Subjects:

  • four groups were formed based on the lesion level; men with quadriplegia (C4/5 through C8, n=8), men with high-level paraplegia (T1-T5, n=5), with med-level paraplegia (T6-T10, n=10), and with low-level paraplegia (T11-L5, n=14)
  • All subjects use a hand propelled wheelchair as primary means of locomotion
  • All men live more or less independently at home and said that they "felt healthy".
  • Seventeen subjects reported medication usage on a regular basis (predominantly antispasticity medication and medicaiton to prevent or control urinary tract infections)
  • One subject (age 71) had had a minor myocardial infarction
  • Eight subjects reported renal problems (eg, kidney stones)
  • Eighteen subjects have had or still had urinary tract infections

Ethnicity: Caucasion

Anthropometrics

 

C4-C8

n=8

T1-T5

n=5

T6-T10

n=10

T11-L5

n=14

Total

N=37

Groups

Different

Age (years)  37.3 +/- 10.0  40.6 +/- 8.3  31.6+/- 6.6  40.6 +/-15.9 37.4 +/- 12.0   
 Time since Injury  17.8 +/- 9.3 19.0  +/-9.5 12.7 +/-8.3 12.9+/-7.9   14.7+/-8.6  
 Body mass (kg)  83.1+/- 15.1  84.7 +/- 11.1  79.7 +/- 16.7 85.6 +/- 21.4  83.3 +/-17.3  
 Sum of 4 skinfolds  67.0+/- 32.2  82.5+/-41.2  65.4+/-31.5 77.1 +/- 35.9  72.5+/-34.7  
 BMI (kg/m2)  23.8+/-3.2  24.6+/-3.3 24.3 +/- 4.8  26.0 +/- 6.0  24.9+/-4.8  
 Sport participation (hrs/week)  4.6+/-4.6  1.2+/-1.8  2.9+/-2.7  2.7+/- 3.5  2.9+/-3.4  
 Alcohol consumption (glasses/day)  0.7+/-0.5  2.0+/-2.1  1.2+/-1.5  1.6 +/- 2.3  1.4 +/-1.8  
 SBP (mmHg)  109.3+/-15.9  127.6+/-16.7  126.4+/-8.8  140.4 +/- 22.1  128.2 +/-18.8  
 DBP (mmHg)  68.8+/-13.2  72.8+/-20.9  77.9+/-9.8  76.2 +/- 15.7  74.6 +/-14.4  1-4
 Vo2 peak (L/min)  1.2+/-0.4  1.4+/-0.2  1.9+/-0.4   2.1 +/- 0.5  1.7 +/-0.6  
 VO2 peak (mL/kg/min)  14.3+/-4.4  17.0+/-2.3  24.3+/-6.1  25.6+/- 8.3  21.5 +/-7.8  1-3, 4,2-4,1-3,4

Summary of Results:

 

Relation with Lesion Level

  • No signifiant differences were found among lesion groups for age, TSI, body mass, BMI, skinfolds, alcohol consumption, sport participation, and DBP.
  • SBP was lower in the group with quadriplegia than low-level paraplegia.
  • Aerobic power was significantly inversely related with the level of the lesion, with the subjects having significantly lower levels than those with mid-andlow-level paraplegia.
  • No significant differences among the lesion groups were found for any of the parameters.

Comparison with an AB Population

  • The perceptage of nonsmokers among the subjects with SCI (23 out of 37 - 62%) is very similar to that (61%) of he AB population.
  • Thirteen (35%) of SCI subjects did not participate in sport while 24% of AB men between 20 and 60 years were classified as inactive (no sport participation and a sedentary job)
  • SUbjects with SCI younger than 30 years had a significantly lower BMI (21.7 +/- 2.8 vs. 23.3 +/-2.8) than the AB subjects in the sam age group. 
  • The prevalence of Grade II obesity was slightly higher in SCI subjects (n=5 [14%]) than AB population.
  • SBP was significantly higher in subjects with SCI younger than 40 years than in AB persons.
  • DBP as significantly lower in subjects with SCI older than 39 years.

Correlations Among Lipid Profile and Blood Pressure

  •   TC was found to be directly related (p<0.01) with LDL-C, apoB, adn TC/HDL-C, and inversely related with HDL-C/LDL-C.
  • HDL-C was significantly inversely related with VLDL-C, TG, and directly related (p<0.05) with apoA-1 and apoA-2. 
  • ApoB was significantly related with LDL-C, TC/HDL-C, and HDL-C/LDL-C. 
  • The ratio apoA-1/apoB reflected the ratios TC/HDL-C and HDL-C/LDL-C.
  • VLDL-C was significantly related to TG.
  • SBP and DBP were only moderately related (r = 0.3) to apoA-2.

Relation Between Lipid and Lipoprotein Profile, Blood Pressure, and Selected Factors

  • TC, LDL-C and apoB were significantly nd directly related to age, TSI, sum of skinfolds, body mass, BMI and smoking behavior, and significantly inversely related to sport participation and Vo2 peak (mL/kg/min). 
  • HDL-C and HDL2-C were directly related to alcohol consumption and inversely related to BMI, body mass, and skinfolds sum.
  • VLDL-C and TG were directly related (p,0.05) to sum of skinfolds, SMI, body mass, age adn TSI and significantly inversely related to aocohol consumption.  The TC/HDL-C ratio was significantly directly related to sum of skinfolds, body mass, age, TSI, and smoking behavior, and inversely (p<0.05) related to alcohol consumption.

Predication of Lipid and (Apo-) Lipoprotein Profile and Blood Pressure

  • Age was the most important predictor of TC, LDL-C, apoB, and of the ratios HDL-C/LDL-C, TC/HDL-C, and apoA-1/apoB. 
  • Smoking behavior explained an additional part of the variance in TC, LDL-C, apoB, TC/HDL-C, and HDL-C/LDL-C.

 

Author Conclusion:
  • Men with SCI do not seem to have an essentially different CHD risk profile in comparison to AB person. 
  • Although HDL-C tends to be slightly lower in AB men, TC and LDL-C are correspondnigly lower, resulting in similar HDL-C/LDL_c and TC/HDL-C ratios. 
  • The higher apoB levels in SCI patients than reported in AB person suggest a moderately higher CHD risk in men with SCI. 
  • Men with SCI, especially older men, seem to have a higher risk of obesity.
  • The lipid and (apo) lipoprotein profile is not related to the lesion level nor to the absolute aerobic power in a hetergeneous group of men with long standing SCI.
  • Important predictors are age, activity level, smoking behavior, alcohol consumption, and adipose tissue - indicating that as in AB populations, modifiable risk factors determine CHD risk.
Funding Source:
University/Hospital: Vrije Universiteit Amsterdam
Reviewer Comments:

Small sample size comprised entirely of volunteers might skew the data somewhat.  Mean age of paricipants was somewhat young to be examining CHD.

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) 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? ???
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? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  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? 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%.) ???
  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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? ???
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? ???
  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? No
  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? No
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? ???
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? No
  6.6. Were extra or unplanned treatments described? No
  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? ???
  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)? Yes
  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? N/A
  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? N/A
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes