Telomeres play an important role in numerous conditions as well as the ageing process.
A telomere is a protective structure at the end of a chromosome which prevents degradation and provides genetic stability. Each time a cell divides, and DNA replication takes place, a part of the genetic information is cleaved off and without telomeres being on the end this would be critical genetic information. This is the protective role of a telomere in a nutshell.
Shortened telomere length is suggested to be associated with many common ageing disease such as cancer, dementia and frailty. Studies have even shown that a longer telomere length results in a lower mortality rate with a shorter length associated with higher mortality. Therefore controlling telomere length could play an important role in healthcare treatment in the future.
Exercise has been thought to be an effective way at slowing the rate of telomere shortening though various pathways including influencing telomerase levels which has been demonstrated in endurance athletes. To date there has been some individual studies which have investigated exercise and telomere length but there hasn’t been a summary of these studies which is why the authors of a new systematic review investigated published in Medicina
This systematic review and meta-analysis followed PRISMA guidance and the authors also pre-registered the protocol on PROSPERO. The literature search took place between October and November 2021 and involved four databases (MEDLINE, EMBASE, CINAHL and PEDro) as well as Google Scholar. The search was performed by combining exercise, telomere length and RCT.
Articles were included within the review if they met the following inclusion criteria:
- Participants weren’t classified according to specific diseases or conditions
- Exercise was the main intervention
- Inactivity or usual care was the control or comparison group
- Telomere length was investigated
- The studies were RCTs
Studies were non-human studies, used interventions which were classed as lifestyle or physical activity or used non-RCTs designs were excluded.
The articles were screened for inclusion by two researchers independent of each other with disagreement resolved through consensus. The study data were extracted using RevMan 5.4 with methodological quality assessed using the Cochrane Risk of Bias 2.0 tool.
Seven studies met the criteria for inclusion which totalled 939 participants. The overall quality of the included studies showed a low risk of bias with the most significant cause of bias coming from attrition bias.
Aerobic exercise appears to be the most effective form of exercise at slowing the decline of telomere length compared to strength training. Furthermore the duration of training the slower the decline however it’s unclear what the ceiling effect might be on rate of slowing. That being said there has been evidence published which suggests exercise performed consistently over 5 years can lengthen telomeres.
In previous literature it has been suggested that moderate-intensity exercise is the most beneficial intensity level of exercise at slowing the decline in telomere length. Combining these results it can be suggested that, aerobic exercise performed at moderate intensity over six months or longer is the most effective method of using exercise to allow the rate of telomere shortening.
There are still questions about which type/form of exercise is most effective at slowing telomere length and some studies are taking place to investigate this. There are also questions to be addressed around the certainty of the findings from the systematic review and meta-analysis we have discussed here because of the publication bias demonstrated by the authors of the paper.
Either way we know that aerobic exercise has a positive effect on numerous chronic conditions through multiple biological pathways which are associated with telomere length. This provides some more clarity of the results of this systematic review even in the light of the publication bias.
Overall the results of this systematic review and mata-analysis suggest that aerobic exercise performed regularly over 6 months slows the rate of decline in telomere length and therefore is likely to have protective effects for many chronic conditions as well as ageing and frailty.