What is multimorbidity and comorbidity?
Many people with chronic conditions do not have a single, predominant condition, but rather they experience multimorbidity—the presence of 2 or more chronic conditions in a person at the same time (AIHW 2021).
The health effect of multimorbidity can be greater than the combined effect of individual conditions, leading to more severe illness, poorer prognosis and premature death. People with multimorbidity generally use more health services, including increased contact with primary health care services, with more complex hospitalisations and poorer outcomes.
People with cardiovascular disease (CVD) often live with other chronic conditions besides CVD. The additional conditions experienced by a person who has CVD is known as comorbidity. In this report, the focus is on the comorbidity of CVD (noting that a person may have more than 1 cardiovascular disease) in combination with diabetes and/or chronic kidney disease (CKD). These 3 diseases are closely associated, with shared underlying causes and risk factors, along with common prevention, management and treatment strategies. The interrelationship between their effects means that diabetes and CKD also act as risk factors for coronary heart disease, stroke and other cardiovascular diseases (AIHW 2016).
An ageing population, along with unfavourable risk factor trends and a high prevalence of chronic disease in the community are expected to result in a rise in the prevalence of CVD comorbidity, and higher rates of CVD among among people with other chronic conditions.
In 2017–18, based on self-reported data, of the estimated 1.2 million Australians who had heart, stroke and vascular disease, 950,000 (82%) also had at least 1 of 9 other selected chronic conditions, including:
- arthritis, 572,000 (49%)
- back problems (dorsopathies), 401,000 (35%)
- mental and behavioural conditions, 342,000 (30%)
- diabetes mellitus, 261,000 (23%)
- asthma, 195,000 (17%)
- osteoporosis, 166,000 (14%)
- chronic obstructive pulmonary disease, 119,000 (10%)
- cancer, 82,400 (7.1%)
- kidney disease, 76,900 (6.6%) (ABS 2018).
Heart, stroke and vascular disease was reported as a comorbidity by 32% of people with kidney disease, 22% of people with diabetes mellitus, 20% of people with chronic obstructive pulmonary disease and 19% of people with cancer (ABS 2018).
Note that these data are based on self-report, and rely on respondents providing accurate information—some conditions, such as chronic kidney disease, are under-reported.
Prevalence of CVD, diabetes and CKD
Reliable estimates of the comorbidity of CVD, diabetes and CKD in the Australian population can be derived from large-scale biomedical health surveys. The most recent of these was the National Health Measures Survey, the biomedical component of the 2011–13 Australian Health Survey (ABS 2013).
In 2011–12, an estimated 4.9 million Australian adults (29%) had CVD or diabetes or CKD (AIHW 2014). Of these, over three-quarters (3.7 million or 22% of adults) had only 1 of CVD, diabetes or CKD, however 1.2 million (7.2% of adults) had at least 2 of CVD, diabetes or CKD:
- 601,000 (3.5%) had CVD and CKD
- 342,000 (2.0%) had CVD and diabetes
- 96,000 (0.6%) had diabetes and CKD
- 182,000 (1.1%) had all 3 conditions (Figure 1).
Men were more likely than women to have all 3 conditions (1.5% compared with 0.6%).
Among adults with CVD, 30% also had diabetes and/or CKD.
The prevalence of comorbidity of CVD, diabetes and/or CKD increased with age, more than tripling between the ages of 18–44 and 65 and over (from 12% to 44%) (AIHW 2014).