Disease burden due to risk factors is known as the attributable burden. It is measured as the number of healthy years of life lost that could have been avoided if exposure to the risk factor had been reduced or completely avoided.
The Australian Burden of Disease Study (ABDS) 2018 estimated the dementia burden attributable to 6 modifiable risk factors, including:
- tobacco use
- overweight and obesity
- physical inactivity
- high blood pressure in midlife (35–64 years)
- high blood plasma glucose
- impaired kidney function.
Note, this is not an exhaustive list of risk factors linked to dementia (for example, low education levels – an established risk factor for dementia – is not included) and only includes risk factors measured in the ABDS 2018. The list of risk factors and measures of additional risk (relative risks) were based on those used in recent Global Burden of Disease studies and a number of epidemiological studies. Refer to What puts someone at risk of developing dementia? for more information on the complete list of established risk factors for dementia.
43% of the dementia burden was attributable to 6 risk factors
Overall, 43% of the dementia burden in 2018 was attributable to the 6 risk factors combined, equivalent to 84,800 DALY. This estimate takes into account the complex pathways and interactions between risk factors, such as the relationship between physical inactivity, overweight and obesity, and high blood pressure in midlife. However, this work does not incorporate the impact of age as a separate risk factor for dementia. Age is the main risk factor for dementia but because it is not a modifiable risk factor, it is not included here.
When looking at each risk factors’ contribution to the total burden due to dementia (Figure 4.5):
- 20% was attributable to overweight and obesity (38,900 DALY).
- 12% was attributable to physical inactivity (23,100 DALY).
- 8.4% was attributable to impaired kidney function (16,700 DALY).
- 7.0% was attributable to high blood plasma glucose (13,900 DALY).
- 3.2% was attributable to high blood pressure in midlife (6,300 DALY).
- 2.2% was attributable to tobacco use (4,300 DALY).
While there was little difference in the proportion of dementia burden attributable to the 6 risk factors between men and women, the number of attributable DALY was often lower in men compared with women. This is due to women overall experiencing a greater amount of burden due to dementia than men.
Between 2011 and 2018, the proportion of dementia burden attributable to the 6 risk factors combined increased by 2%. However, this varied when looking at each risk factor. The proportion of dementia burden attributable to high blood pressure in midlife and tobacco use decreased (by 22% and 10%, respectively) whereas this increased for overweight and obesity (by 9.0%) and high blood plasma glucose (3.5%). For impaired kidney function and physical inactivity, this was stable over time.