Comprehensive Twin Study Looks at Cardiometabolic Diseases

Cardiometabolic diseases such as type 2 diabetes, heart disease and stroke are a growing challenge in society. With an aging population and improved healthcare, people are living longer with cardiometabolic diseases more likely to get two or more of these conditions in a lifetime, known as cardiometabolic multimorbidity. It affects an estimated 30% of older adults and leads to increased mortality.

A group of researchers from the Karolinska Institute (Solna, Sweden) reported in the European Heart Journal the results of an 18-year study of twins over the age of 60 who were registered in the Swedish Twin Registry between March 1998 and December 2002. The more than 17,000 individuals were categorized based on whether they had one or more cardiometabolic diseases or whether they were free of these conditions.

The authors discovered that cardiometabolic multimorbidity is linked to a more than doubled risk of vascular dementia and a 50 per cent increased risk of Alzheimer’s disease.  For each cardiometabolic disease the person had, the risk of all types of dementia increased by 42 per cent. The corresponding figure for Alzheimer’s disease is 26 per cent and 64 per cent for vascular dementia.

The study also found that the risk of developing dementia was higher if a person was diagnosed with cardiometabolic diseases in middle age compared to if those diseases developed later in life. According to the study, one explanation for this may be that if the disease debuts earlier in life, it can be a more aggressive form.

These findings underscore the need for special monitoring of individuals with cardiometabolic diseases to reduce their risk of developing dementia at an older age.

The researchers also took a closer look at about 400 specific pairs of twins from the study population that were “mismatched” – that is, the two twins in a pair differed from each other in terms of both the prevalence of cardiometabolic disease and the possible development of dementia.

Among the mismatched dizygotic twins who share 50% of their genes, the twin with cardiometabolic disease was more likely to also be the one who developed dementia. However, among mismatched pairs of identical twins who are genetic copies of each other, the risk of dementia was similar for both twins regardless of cardiometabolic disease status. The results suggest that the same genetic factors may contribute to both cardiometabolic diseases and dementia.