Risk factors for multimorbidity of cardiovascular diseases in the prospective Million Women Study

Cardiovascular diseases often occur together, but little is known about what increases the risk of developing cardiovascular multimorbidity (CVM), particularly in women. This study investigated the associations of cardiovascular risk factors with CVM incidence in UK women.

1.3 million women aged 50-64 years were recruited into the Million Women Study in 1996-2001. Women reported information on demographic and cardiovascular risk factors (weight, height, smoking, alcohol consumption, physical activity and treatment for high blood pressure, diabetes and high blood cholesterol) at baseline. Using linked hospital admission and death records, each participant was followed for 19 subtypes of incident cardiovascular disease. Outcomes were CVM (having ≥2 of 19 selected cardiovascular disease diagnoses), complex CVM (having ≥4 diagnoses), and pairs of the four most common individual cardiovascular diseases.

In multivariable adjusted models, obesity, current smoking and treatment for diabetes or hypertension were each independently associated with a 2-3 times higher risk of incident CVM. Severe obesity, heavy smoking and diabetes were associated with 3-4 times higher risks of complex CVM and most CVM pairs. The strongest relationships were for severe obesity, which was associated with a fivefold higher risk of developing both atrial fibrillation and heart failure together (compared with healthy body mass index), and for diabetes, which was associated with a fivefold higher risk of developing both ischaemic heart disease and heart failure together. There was little evidence of strong associations of alcohol consumption or physical activity with most CVM outcomes.

In middle-aged women, known cardiovascular risk factors including smoking and obesity were associated with substantially higher risks of CVM, with stronger associations for severe obesity, heavy smoking and diabetes, and certain combinations of cardiovascular disease subtypes. Targeted management of these risk factors for secondary prevention may reduce progression to CVM, potentially with greater benefits in those at risk for complex CVM.