A shared genetic link might explain multimorbidity in families

In a guest blog, Dr Oliver van Hecke, DPhil student in Oxford University’s Nuffield Department of Primary Care Health Sciences and Oxfordshire GP, explains why genetics may determine whether someone experiences multiple chronic diseases.

Chronic pain, depression and heart disease are three of the commonest causes of disability, and are becoming more prevalent in the population. Increasingly, some people will suffer from one or several of these long-term health problems in their lifetime, which is known as multimorbidity, but why? Is this simply down to bad luck or could there be an underlying cause, perhaps due to a shared familial risk, and/or genetic factors?

While we know that age, gender, social circumstances and lifestyle increase someone’s vulnerability to multiple causes of disability, research has now revealed that genetics can indeed play a role in determining whether someone experiences multiple chronic illnesses.

The new study, which we were involved with along with colleagues at the University of Dundee and Kings College, London, examined two major existing population cohorts (Generation Scotland and TwinsUK), for the likelihood of chronic pain, depression and heart disease co-occurring in both individuals and in their siblings. We found that people who had one of these illnesses were much more likely to have one or both of the other illnesses.

Interestingly, we identified a sibling link – the brothers or sisters of people with one of these illnesses were much more likely to have one of the other illnesses too, even after allowing for known social and demographic factors. For example, siblings of people with heart disease were twice as likely to have chronic pain, while siblings of those with depression were twice as likely to suffer from heart disease.

Using the twins data, we were able to show that genetics contributed to the co-occurrence of chronic widespread pain and heart disease in twins, in addition to important environmental contributions.

The finding that genes likely play a key role in determining whether someone experiences multiple chronic illnesses provides researchers new avenues to explore the underlying biological mechanisms between different conditions. Of course, as both a researcher and a clinician I realise it will always be important to address the social and demographic factors that cause disability and comorbidity, such as deprivation for example. However this new insight into the shared genetics of comorbidities may enable us to recognise these conditions earlier in the community. This would, in turn, allow us to focus on preventative therapies for these patients by targeting the underlying causes (such as stress or health inequalities) rather than the visible symptoms of the condition itself.

The full study, ‘Chronic pain, depression and cardiovascular disease linked through a shared genetic predisposition: Analysis of a family-based cohort and twin study,’ can be read in the journal PLOS ONE.