The Problem With Anti-Ageing Studies In Animals

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We spend a lot of time covering new discoveries and straightforward interventions that could potentially lead to slower ageing in humans. We believe that so long as an intervention is safe, there’s usually little reason not to adopt it. Most interventions we cover will at worst simply improve health without necessarily affecting the ageing process or leading to increased lifespan. However, it must be remembered that no intervention has yet been proven to delay ageing or to extend lifespan in humans. Most good ideas about how human lifespan might be extended are based on animal experiments, but there’s really no telling if the results of these experiments will translate to humans. Animal research concerning interventions targeting ageing as a whole has many flaws, and it’s worth highlighting these flaws from time to time.

What follows are some of the biggest problems with animal research in this field that should ideally be addressed if we are to improve the quality of anti-ageing research and maximise the chances that findings will translate to humans.

Incomplete Method Reporting

As we all know, scientific studies need to be repeatable, which means that authors ought to report how they conducted their study in sufficient detail for other scientists to replicate the study. Unfortunately, the frequency of reporting of essential features is significantly lower in anti-ageing research compared to studies on other diseases. This can make it hard to assess the validity of a given study, but also means that different studies investigating the same intervention are often using different techniques, making it hard to compare and combine their findings.

Inconsistent Outcomes

Following on from incomplete methods, the quality of reporting and the magnitude of the effects of anti-ageing interventions varies considerably. Findings in non-mammalian species often don’t translate to mammalian models, which makes it hard to extrapolate findings from simpler organisms to more complex ones such as humans. More studies that include both simple and complex organisms could help us better understand why some findings don’t translate well, but such studies are currently low in number.

No Standardised Control Groups

Control groups are essential to the study of any medical intervention, and lifespan extension is no exception. To know if your intervention extends lifespan, you need to know how long animals treated with a control intervention live so that you have something to compare with the treated animals. The problem is that when you compare different animal studies of lifespan extension, you find that the control animals in different studies live for different lengths of time – even when exactly the same genetic strain of animal is being used. This is because factors such as diet, animals per cage, temperature and light cycles can all influence lifespan.

Ideally, the entire field should be using standardised control conditions, but because they do not, it is often hard to compare the results from different studies or assess the true impact of an intervention. For example, if an intervention extends lifespan in study A but not study B, how can we be sure that the intervention was not simply compensating for some difference in housing condition in study A?

Inbred Mouse Models

A great many animal studies of anti-ageing interventions use a highly inbred strain of mouse called C57BL/6 (BL/6 for short). These mice develop many health problems that wild, non-inbred mice don’t get. Much as in the case of housing conditions, this can make it hard to know if an intervention is actually affecting ageing, or merely compensating for the specific set of genetic issues that these mice suffer from. The lack of genetic diversity among BL/6 mice is also a hindrance to translating findings to humans, because wild mammalian species (humans included) are genetically diverse. An intervention is likely to have a similar effect on all BL/6 mice, but might not work the same way in all humans.

Interventions Start Too Early

Many studies initiate interventions targeting ageing very early in the organism’s lifespan, often before sexual maturity. While interventions that slowed ageing in early life would be beneficial in humans, we’re not going to be testing anti-ageing interventions on children. We ideally need interventions that work to slow ageing and prevent or reverse age-related diseases in late life, so the lack of late-life intervention studies is problematic for understanding their relevance to human health.

Publication Bias

Regrettably and just as in many areas of science, there is evidence that smaller (and therefore less powerful) studies with positive findings are more likely to be published than those with negative findings. This distorts the overall picture of the effectiveness of anti-ageing interventions.

Lack of Data Standardisation

There is no universally accepted standard for conducting and reporting lifespan studies. Researchers often don’t use the same metrics for lifespan extension and don’t report their data in the same way. This makes it difficult to compare and combine data across studies in order to obtain a more accurate picture of how well an intervention works.

Small Sample Sizes

While some compounds show significant lifespan increases in both non-mammalian and mammalian models, the number of mammalian experiments and sample sizes are often quite small. Small sample sizes reduce the statistical power of a study, which essentially increases the likelihood that differences between the control group and the intervention were attributable to random chance.

It’s not all doom and gloom – there are still good quality animal studies that demonstrate promising interventions for slowing the ageing process. The issue is that such studies exist in isolation, and often cannot be easily compared to other research. Any efforts to compile all this data together and paint a bigger picture is hindered by the fact that everyone has their own idea about how the study of ageing should be conducted and how the results should be reported.

In some ways this is a symptom of a good thing – that this field of research is still comparatively fresh, not yet dominated by any particular dogma, and so a lot of people with different ideas are trying to expand our knowledge in different directions. If we humans want to benefit from this knowledge as soon as possible, though, it would be a good idea to agree on more standardised and rigorous approaches to designing and reporting the results of these studies.