Are telomeres the biological key to multimorbidity?
Dr Claire Niedzwiedz is a Research Associate at the University of Glasgow Institute of Health & Wellbeing funded by a Medical Research Council Fellowship exploring the overlap between physical and mental health conditions. She tweets @DrCeNz
Multimorbidity is an increasing global public health concern. It can be defined as the co-existence of two or more chronic health conditions and is influenced by a range of factors including age and socioeconomic deprivation. However, we know little about the potential biological mechanisms underlying the development of multimorbidity, or its consequences for our biology.
Telomeres are repetitive nucleotide sequences (of TTAGGG) at the end of chromosomes that protect the genome from damage. Research demonstrates that individuals with a range of health conditions, such as cardiovascular disease, psychiatric disorders and some cancers, tend to have shorter telomeres (longer telomeres appear to be protective). Shorter telomere length is also associated with an increased risk of mortality. Few studies have examined whether multimorbidity is related to shorter telomeres, over and above the influence of having a single health condition. This was the focus of our study recently published in Age and Ageing.
We analysed telomere lengths from 5,495 people who took part in the Health and Retirement Study, a nationally representative longitudinal survey of individuals aged over 50 years in the USA. In 2008 participants who provided a saliva sample enabled the measurement of salivary telomere length. We combined this biological data with the range of information provided by four waves of the survey from 2008 to 2014, which included data on various aspects of people’s lives, including their social circumstances and health.
We had three key objectives. The first was to examine the individual relationships between telomere length and a number of chronic diseases (including high blood pressure; diabetes; cancer; chronic lung disease; heart problems; stroke; psychiatric problems; and arthritis). We explored whether telomere length was related to multimorbidity using different ways to define it (including a standard approach comparing those with one or no health condition to those with two or more conditions; a score-based approach counting the number of health conditions present; and distinguishing physical multimorbidity from multimorbidity including psychiatric problems). In prospective analyses, we also investigated whether telomere length measured in 2008 predicted the development of multimorbidity from 2010 to 2014.
We found that men with longer telomeres had reduced risk of psychiatric problems and lung disease, taking into account important factors such as education level, ethnicity, smoking and body mass index. Men with longer telomeres also had reduced risk of multimorbidity that included psychiatric problems, but this was not the case for physical multimorbidities. Telomere length was not related to the onset of multimorbidity in prospective analyses for men or women.
So, are telomeres the biological key to multimorbidity? Our research suggests not, but there is more research to do. Further exploration that digs deeper into whether there is a potential causal relationship between telomere length and psychiatric conditions, as well as other specific comorbid conditions like cardiovascular disease, will help increase our understanding of these important and fascinating biological markers.