Animal experiments provide a basis for decisions on the design and conduct of subsequent clinical trials. Our work evaluates the efficacy of statins in animal studies to provide an overall synthesis that facilitate the interpretation of aggregated data from the basic research conducted so far. What is the evidence from laboratory animals on the effects of statins in decreasing cholesterol levels and preventing or ameliorating cardiovascular diseases?

1. Systematic review of
animal studies
The case of statins
Pecoraro V, Moja L, Dall'Olmo L, Cappellini G, Garattini S. Most appropriate
animal models to study the efficacy of statins: a systematic review.
Eur J Clin Invest. 2014;44(9):848-71. doi: 10.1111/eci.12304.
Moja L, Pecoraro V, Ciccolallo L, Dall'Olmo L, Virgili G, Garattini S. Flaws
in animal studies exploring statins and impact on meta-analysis.
Eur J ClinInvest. 2014;44(6):597-612. doi: 10.1111/eci.12264.

2. Our work evaluates the efficacy of statins in animal
studies to provide an overall synthesis that facilitate the
interpretation of aggregated data from the basic
research conducted so far.
Methods: We have aggregated the findings in animal
models - mice, rats and rabbits - using the technique of
systematic review and meta-analysis.
We included 161 animal studies and we analysed 120
studies, accounting for 2432 animals.

3. Total Cholesterol (TC): reduction in all animal
models
Rats
-10%
Mice
-20%
Rabbits
-30%

4. Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71

5. Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71

6. Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71

7. Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71

8. Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71

9. Overall estimate for blood pressure reduction and infarct size
in each animal model and strain
Blood pressure reduction
Animal
model
Strain Studies included Studies Total
sample
Overall estimate (mmHg) Heterogene
ity†
Test for
subgroup
differenc
es*
N N MD 95% CI P I² P
MICE Apo E-/- All ‡ 3 84 -4 [-8 ; -1] 0,01 0%
RATS Spontaneously
Hypertensive
All 14 239 -17 [-24 ; -10] <0,001 95%
St diet 11 201 -20 [-32 ; -9] <0,001 94% <0,001
HC diet 3 38 -6 [-15 ; 2] 0,2 91%
Sprague
Dawley
All ‡ 10 201 -5 [-12 ; 1] 0,1 49%
Wistar All ‡ 5 82 -10 [-26 ; 7] 0,3 86%
Infarct size
Animal
model
Strain Included studies Studies Total
sample
Overall estimate (%) Heterogene
ity†
N N SMD 95% CI P I²
RATS Sprague
Dawley
All 6 101 -1 [-2 ; -0,3] 0,009 75%
Wistar All 3 65 -0,5 [-1,6 ; 0,6] 0,4 77%

10. Main results
Statins lowered the total cholesterol across all species,
although with large differences in the effect size: -30% in
rabbits, -20% in mice and -10% in rats.
The reduction was larger in animals fed on a high-cholesterol
diet.
Statins reduced infarct volume but did not consistently
reduce the blood pressure or effect the overall survival.
Few studies considered strains at high risk of
cardiovascular diseases or hard outcomes.

11. Review authors’ judgments about each risk of bias item
presented as percentages across all included studies
Moja et al. Eur J Clin Invest. 2014;44(6):597-612

12. Meta-analysis
graph
for Rats using
Ratio Of Means
•Point estimate
•Confidence interval
•Prediction interval
•Fixed vs random effects
model
Moja et al. Eur J Clin Invest. 2014;44(6):597-612

13. Meta-analysis graph for Mice using
Ratio Of Means
Moja et al. Eur J Clin Invest. 2014;44(6):597-612

14. Meta-analysis
graph
for Rabbits
using
Ratio Of Means
Moja et al. Eur J Clin Invest. 2014;44(6):597-612

15. Counter-enhanced funnel plots to explore small studies effects in
Mice, Rabbits and Rats
The funnel plots of the three animal models suggested that the effect
size of studies were highly variable, overall, in both direction and
magnitude.
Most of the studies had high precision; this was clearly displayed in the
general funnel plot in which most of them gathered at the top
Moja et al. Eur J Clin Invest. 2014;44(6):597-612

16. Main results
• Our systematic review highlights the inadequate experimental
reporting: over half did not report design quality components
(randomisation and blinding), many omitted information about
animal gender, age or weight, all did not report the sample size.
• The description of characteristics was consistently
unsatisfactory and it can result in such studies being un-interpretable
and difficult to reproduce.
• Fixed- and random-effects models gave different results: ratio
of effect size increased by !! five folds !!
• Ratio Of Means model occasionally preferable in animal
studies.
• Heterogeneity was consistently substantial. Accounting for
covariates had minimal impact.
• Publication bias is highly suspected across studies.

17. Taylor 2012, The Cochnale Library Issue 5
Humans
Pecoraro et al. Eur J Clin Invest. 2014;44(9):848-71
Mortality
Rats
Mice

18. Conclusions
Heterogeneity was consistently substantial, raising questions
about the appropriateness of a cumulative approach.
Results of meta-analyses in animal studies – statins - were
difficult to interpret and reproduce.
Different meta-analytic approaches were proved to be largely
inconsistent, suggesting tha reliable meta-analystic approaches
cannot be not widely used in animal studies.
Policies that address these issues are required from
investigators, editors and institutions that care about the quality
standards and ethics of animal research.