H/A: Micronutrient Supplementation (2009)

Citation:
 
Study Design:
Class:
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Quality Rating:
Research Purpose:

The study was designed to examine the effect of vitamin supplements on pregnancy outcomes, vertical transmission of HIV and other health and survival end-points during several years after delivery from the index pregnancy.

Inclusion Criteria:

HIV-infected pregnant Tanzanian women between 12 and 27 weeks of gestational age at enrollment.

Exclusion Criteria:
  • Non HIV-infected women
  • Non-pregnant women.
Description of Study Protocol:
  • Recruitment: Pregnant women who attended four prenatal care clinics in Dar es Salaam, Tanzania
  • Design: Randomized placebo-controlled trial 
  • Blinding used: Single-blind.

Intervention

  • At the first prenatal visit, HIV-infected women were randomly assigned to one of four daily oral regimens in a 2x2 factorial fashion:
    • Multi-vitamins (thiamine, riboflavin, vitamin B6, niacin, vitamin B12, vitamin C, vitamin E and folic acid)
    • Pre-formed vitamin A plus beta-carotene (VA/BC)
    • Multi-vitamin including VA/BC
    • Placebo.
  • Supplementation continued during the first two years postpartum and thereafter. Children were weighed and measured monthly and all received vitamin A supplements after six months of age, per the standard of care.
  • The active treatment and placebo tablets were indistinguishable.

Statistical Analysis

  • Baseline characteristics
    • Kruskal-Wallis tests for continuous variables
    • Chi-square tests for proportions.
  • Continuous outcomes
    • Mixed-effects models for average growth curves
    • Likelihood test.
  • Binary outcomes
    • Cox models.
Data Collection Summary:
  • Timing of measurements: At or after delivery and at up to 24 months
  • Dependent variables: Infant growth in weight, length, head circumference and arm circumference, weight for age, weight for length and length-for-age Z-scores.

Independent Variables

  • At the first prenatal visit, HIV-infected women were randomly assigned to one of four daily oral regimens in a 2x2 factorial fashion:
    • Multi-vitamins (thiamine, riboflavin, vitamin B6, niacin, vitamin B12, vitamin C, vitamin E and folic acid)
    • Pre-formed vitamin A plus beta-carotene (VA/BC)
    • Multi-vitamin including VA/BC
    • Placebo
    • Supplementation continued during the first two years postpartum and thereafter. Children were weighed and measured monthly and all received vitamin A supplements after six months of age, per the standard of care. 
  • Compliance, defined as the number of tablets absent from the returned bottles at monthly visits, divided by the total number of tablets the individual must have taken, was 83% on average.
Description of Actual Data Sample:
  • Initial N: 1,085 women resulted in 886 mother-infant pairs. Dropouts were non-pregnant, died before delivery, were twins, had a date of delivery or outcome of pregnancy that was unknown, fetal deaths or lacked postnatal anthropometric measures.
  • Attrition (final N): 886 singleton born
  • Age: Mothers, 24.8±4.8 years; infants, birth to 24 months
  • Ethnicity: Not reported.

Other Relevant Demographics

  • Mean CD4 counts
    • Placebo (N=208): 451±268 cells per mm3
    • Vitamin A and beta-carotene alone (N=224): 440±272 cells per mm
    • Multi-vitamins (N=222): 453 ± 259 cells/mm3
    • Multi-vitamins, vitamin A and beta-carotene (N= 232): 428±235 cells per mm3.

Anthropometrics

Pregnant women baseline characteristics did not differ significantly.

Location

Four prenatal care clinics in Dar es Salaam, Tanzania.

Summary of Results:
  • Multi-vitamins had a significant positive effect on attained weight (459g; 95% CI: 35, 882; P=0.03) and on weight-for-age (0.42; 95% CI: 0.07, 0.77; P=0.02) and weight-for-length (0.38; 95% CI: 0.07, 0.68; P=0.01) Z-scores at 24 months
  • VA/BC seemed to reduce the benefits of multi-vitamin on these outcomes
  • No significant effects were observed on length, mid-upper arm circumference or head circumference.  

Table Two: Effect of Vitamin Supplementation of HIV-Infected Women on Infant Growth in Weight, Length, Head Circumference and Arm Circumference Between Birth and 24 Months of Age in Tanzania1

End-Point
Placebo
(N=208)
Vitamin A+Beta-Carotene Alone
(N=224)
Multi-Vitamins
(N=222)
Multi-Vitamins and Vitamin A+Beta-Carotene
(N=232)
Value
Difference
(95% CI)
Value
Difference
(95% CI)
Value
Difference
(95% CI)
Weight
(g)
0 months
(birth)
2,916±462
2,992±37
76
(-40, 193)
3,109±34
194
(81, 306)
3,019±40
104
(-16, 223)
6 months
7,014±97
7,107±79
92
(-153, 338)
7,105±79
90
(-155, 336)
7,186±78
171
(-73, 415)
12 months
8,173±108
8,227±102
54
(-238, 346)
8,364±87
191
(-81, 463)
8,327±92
155
(-124, 433)
18 months
9,167±131
9,055±123
-112
(-464, 240)
9,335±109
168
(-165, 501)
9,317±117
150
(-193, 494)
24 months
9,898±168
9,907±153
9
(-436, 453)
10,357±137
459
(35, 882)
10,113±153
215
(-229, 659)
Length
(cm)
0 months
(birth)
49.0±0.2
49.0±0.2
0.02
(-0.55, 0.60)
49.4±0.2
0.41
(-0.16, 0.98)
49.0±0.2
0.05
(-0.51, 0.60)
6 months
64.3±0.2
64.4±0.2
0.14
(-0.52, 0.80)
64.6±0.2
0.28
(-0.36, 0.93)
64.6±0.2
0.33
(-0.30, 0.96)
12 months
71.1±0.3
71.2±0.2
0.11
(-0.62, 0.84)
71.2±0.3
0.13
(-0.61, 0.87)
71.2±0.2
0.10
(-0.61, 0.82)
18 months
76.4±0.3
76.5±0.3
0.08
(-0.77, 0.92)
76.7±0.3
0.24
(-0.60, 1.07)
76.6±0.3
0.15
(-0.67, 0.98)
24 months
80.6±0.4
80.2±0.3
-0.40
(-1.40, 0.60)
81.0±0.3
0.36
(-0.61, 1.34)
80.5±0.3
-0.12
(-1.13, 0.89)
Head circumference
(cm)
0 months
(birth)
34.3±0.1
34.5±0.1
0.20
(-0.11, 0.51)
34.7±0.1
0.36
(0.08, 0.65)
34.5±0.1
0.19
(-0.11, 0.48)
6 months
42.7±0.1
42.8±0.1
0.14
(-0.22, 0.49)
42.7±0.1
0.03
(-0.32, 0.38)
42.9±0.1
0.25
(-0.11, 0.61)
12 months
45.1±0.1
45.2±0.1
0.09
(-0.25, 0.43)
45.3±0.1
0.14
(-0.17, 0.45)
45.3±0.1
0.20
(-0.12, 0.52)
18 months
46.4±0.1
46.5±0.1
0.07
(-0.29, 0.42)
46.4±0.1
0.03
(-0.31, 0.37)
46.6±0.1
0.17
(-0.17, 0.50)
24 months
47.1±0.1
47.3±0.2
0.15
(-0.27, 0.57)
47.3±0.1
0.16
(-0.24, 0.56)
47.2±0.1
0.11
(-0.28, 0.51)
Midupper arm circumference
(cm)
1 month
11.7±0.1
11.6±0.1
-0.16
(-0.51, 0.20)
12.0±0.1
0.26
(-0.08, 0.61)
11.8±0.1
0.10
(-0.25, 0.45)
6 months
13.7±0.1
13.8±0.1
0.05
(-0.25, 0.36)
13.8±0.1
0.10
(-0.20, 0.41)
13.8±0.1
0.02
(-0.29, 0.33)
12 months
13.9±0.1
14.0±0.1
0.04
(-0.28, 0.36)
14.1±0.1
0.22
(-0.07, 0.51)
14.1±0.1
0.21
(-0.09, 0.51)
18 months
14.1±0.1
14.0±0.1
-0.17
(-0.49, 0.15)
14.1±0.1
-0.05
(-0.35, 0.25)
14.2±0.1
0.04
(-0.27, 0.35)
24 months
14.1±0.1
14.1±0.1
-0.03
(-0.41, 0.34)
14.4±0.1
0.27
(-0.08, 0.62)
14.2±0.1
0.05
(-0.33, 0.43)

1: Mean values were estimated from cubic spline models with each anthropometric variable as the outcome and predictors that included treatment, spline variables for age and interaction terms between treatment and the age spline terms. Differences reflect the treatment effect compared with the placebo group at each time point; 95% CIs for the differences were constructed by using robust estimates of the variance. In a main-effects model that compared children whose mothers received multi-vitamins or multi-vitamins and vitamin A plus beta-carotene with children whose mothers did not receive multi-vitamins (i.e., received placebo or vitamin A plus beta-carotene alone), the average effect of multi-vitamins on attained weight at 24 months of age was 331g (95% CI: 42, 619 g; P=0.03). However, an interaction between multi-vitamins and vitamin A plus beta-carotene on weight was statistically significant (P for interaction =0.004, likelihood ratio test), whereby, vitamin A plus beta-carotene decreased the effect of multi-vitamins on attained weight, as shown in this table. The main effects of vitamin A plus beta-carotene alone were not significant. Neither multi-vitamins nor vitamin A plus beta-carotene alone had significant effects on length, head circumference or mid-upper arm circumference and there were no significant interactions between the two treatment arms on these outcomes.
2: ±SE (all such values).

Table Four: Effect of Vitamin Supplementation of HIV-Infected Women on the Post-Natal Incidence of Stunting, Wasting and Underweight in their Infants in Tanzania

Outcome1
Placebo
Vitamin A+ ß-Carotene Alone
Multi-Vitamins
Multi-Vitamins and Vitamin A + Beta-Carotene
HR
(95% CI), Main Effect of Multi-Vitamins2
HR
(95%), Main Effect of Vitamin A + Beta-Carotene3
Wasting

 

 

 

 

0.77
(0.56, 1.08)4
0.73
(0.52, 1.00)5
  No. at risk6
158
183
172
184

 

 

Child months of follow-up
2,014
2,558
2,423
2,573

 

 

No. of events
37
40
40
26

 

 

HR
(95% CI)7
1.00
0.83
(0.53, 1.29)
0.88
(0.56, 1.37)
0.53
(0.32, 0.88)

 

 

Underweight

 

 

 

 

0.77
(0.60, 0.98)8
0.89
(0.90, 1.14)4
  No. at risk6
170
193
196
198

 

 

Child months of follow-up
2,000
2,361
2,492
2,574

 

 

No. of events
58
76
69
53

 

 

HR
(95% CI)7
1.00
1.06
(0.75, 1.49)
0.92
(0.65, 1.31)
0.67
(0.46, 0.97)

 

 

Stunting

 

 

 

 

0.92
(0.73, 1.16)4
0.88
(0.70, 1.11)4
  No. at risk6
165
178
177
180

 

 

Child months of follow-up
1,742
2,123
2,053
2,191

 

 

No. of events
68
76
76
70

 

 

Hazard ratio
(95% CI)7
1.00
0.90
(0.65, 1.25)
0.94
(0.68, 1.31)
0.81
(0.58, 1.13)

 

 

1: Wasting, underweight and stunting were defined from weight-for-length, weight-for-age and length-for-age Z-scores, respectively, as under -2. The World Health Organization/National Center for Health Statistics reference (16) was used to calculate the Z-scores. HR=hazard ratio.
2: Comparison of children whose mothers received multi-vitamins alone or multi-vitamins and vitamin A plus beta-carotene with children whose mothers received vitamin A plus beta-carotene alone or placebo
3: Comparison of children whose mothers received vitamin A plus beta-carotene alone or multi-vitamins and vitamin A plus beta-carotene with children whose mothers received multi-vitamins alone or placebo
4: NS (Wald test)
5: P=0.06 (Wald test)
6: Only subjects without the outcome at baseline were considered to be at risk
7: From Cox proportional hazards models with time-to-event as the outcome and treatment as the predictor. The reference category was the placebo group.
8: P=0.03 (Wald test).

Author Conclusion:
  • In conclusion, supplementation of HIV-infected women during pregnancy and lactation with multi-vitamins at several times the recommended dietary allowance is associated with a greater weight gain in their children during the first two years of life
  • Long-term daily multi-vitamin supplementation has been recommended to HIV-infected persons because of its protective effects against disease progression. The benefits on child growth that we presently report further strengthen the rationale for such recommendation.
  • The effect of vitamins B, C and E on growth endpoints, when administered directly to HIV-infected or -uninfected children, needs to be considered in future research
  • The effects among HIV-uninfected pregnant women on growth and child health outcomes also deserve evaluation in clinical trials.
Funding Source:
Government: National Institute of Child Health and Human Development, Fogarty International Center
Reviewer Comments:

Authors note the following limitations:

  • Measurement error of anthropometric variables, especially length, could have reduced the statistical power to detect potentially significant treatment effects
  • Although the frequency of intake from the treatment regimen was high, any lack of compliance may also affect the comparisons by biasing the estimate toward the absence of effect
  • Although efforts were made to obtain anthropometric data as scheduled and follow-up was very high, the random presence of missing values could reduce statistical power.
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.) 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? 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? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  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? Yes
  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