Twin research is now looking at how the differences in twins can help us determine the reasons behind healthy or unhealthy aging.
Twins have always been a source of fascination, even as far back as the legend of the birth of the city of Rome that involved twins Romulous and Remus. Aristotle (384-322BC) felt that twins were monstrosities that were caused by the overabundance of semen and Saint Albertus Magnus (1193-1280AD) thought that conjoined twins occurred to the incomplete division of sperm (a theory that is not that far removed from the truth). Even avid readers of Shakespeare (1564-1616AD) may have noted that being the father of opposite sex twins had an influence on his work, notably “The Comedy of Errors” and Twelfth Night”.
Even identical members of TwinsUK based at King’s College London, the largest adult Twin registry in the UK, have confessed that they find other identical twin pairs fascinating, often staring at them, even though they do not enjoy being the centre of attention as twins themselves.
Scientifically, the sameness of twins was the reason that the TwinsUK registry was created by Professor Tim Spector in 1992. As a consultant rheumatologist, Professor Spector noticed that if he saw a twin in his clinic, invariably the co-twin would present with the same symptoms and disease in the future. The TwinsUK registry was hence created and initially collected a few hundred pairs of middle-aged female twins. Since then, the TwinsUK registry has grown and now hosts a longitudinal collection of data on over 13,000 identical and non-identical, male and female twins and focuses on health and diseases of aging Twin research volunteers attend a research visit that is akin to a health MOT and as a result the data on these twins includes a vast array of health and lifestyle information, physical measures, biochemical results, DXA data (looking at bone density , as well as fat and lean mass), genetic and epigenetic data, metabolomics, glycomics and the gut microbiome.
Twins offer the unique opportunity in research as they can be akin to a randomised controlled trial. Identical twins have shared their genetics (100% of their DNA), inter-uterine and childhood environment, whereas non-identical twins share approximately 50% of their DNA (the same as singleton siblings), but have shared an inter-uterine and childhood environment. By looking at how similar identical twins are compared to non-identical twins, it is possible to determine whether a disease or trait of interest has a genetic or environmental basis.
The focus of the research at the Department of Twin Research has also taken an interesting turn in recent years. It has become apparent from following the twins longitudinally, that identical twins might not be as identical as first thought. As the twins within the cohort age, many identical twins are becoming discordant for a wide range of traits and diseases, such as obesity, depression, type 2 diabetes and osteoporosis (to name but a few) i.e. on twin develops a disease and the other doesn’t.
So from a starting point of looking at the similarities of twins to help determine how we age or how diseases develop, twin research is now looking at how the differences in identical twins can help us determine the reasons behind healthy or unhealthy aging.