### Abstract

Background: At present, dementia has no known cure. Interventions to delay onset and reduce prevalence of the disease are therefore focused on risk factor reduction. Previous population attributable risk estimates for western countries may have been underestimated as a result of the relatively low rates of midlife obesity and the lower weighting given to that variable in statistical models. Methods: Levin’s Attributable Risk which assumes independence of risk factors was used to calculate the proportion of dementia attributable to seven modifiable risk factors (midlife obesity, physical inactivity, smoking, low educational attainment, diabetes mellitus, midlife hypertension and depression) in Australia. Using a recently published modified formula and survey data from the Australia Diabetes, Obesity and Lifestyle Study, a more realistic population attributable risk estimate which accounts for non-independence of risk factors was calculated. Finally, the effect of a 5-20% reduction in each risk factor per decade on future dementia prevalence was computed. Results: Taking into consideration that risk factors do not operate independently, a more conservative estimate of 48.4% of dementia cases (117,294 of 242,500 cases) was found to be attributable to the seven modifiable lifestyle factors under study. We calculated that if each risk factor was to be reduced by 5%, 10%, 15% and 20% per decade, dementia prevalence would be reduced by between 1.6 and 7.2% in 2020, 3.3-14.9% in 2030, 4.9-22.8% in 2040 and 6.6-30.7% in 2050. Conclusion: Our largely theory-based findings suggest a strong case for greater investment in risk factor reduction programmes that target modifiable lifestyle factors, particularly increased engagement in physical activity. However, further data on risk factor treatment and dementia risk reduction from population-based studies are needed to investigate whether our estimates of potential dementia prevention are indeed realistic.

Original language | English |
---|---|

Article number | 11 |

Journal | Alzheimer's Research and Therapy |

Volume | 9 |

Issue number | 1 |

DOIs | |

Publication status | Published - 17 Feb 2017 |

Externally published | Yes |

### Keywords

- Australia
- Dementia
- Population attributable risk

### Cite this

*Alzheimer's Research and Therapy*,

*9*(1), [11]. https://doi.org/10.1186/s13195-017-0238-x

}

*Alzheimer's Research and Therapy*, vol. 9, no. 1, 11. https://doi.org/10.1186/s13195-017-0238-x

**Proportion of dementia in Australia explained by common modifiable risk factors.** / Ashby-Mitchell, Kimberly C ; Burns, Richard; Shaw, Jonathan; Anstey, Kaarin J.

Research output: Contribution to journal › Article › Research › peer-review

TY - JOUR

T1 - Proportion of dementia in Australia explained by common modifiable risk factors

AU - Ashby-Mitchell, Kimberly C

AU - Burns, Richard

AU - Shaw, Jonathan

AU - Anstey, Kaarin J.

PY - 2017/2/17

Y1 - 2017/2/17

N2 - Background: At present, dementia has no known cure. Interventions to delay onset and reduce prevalence of the disease are therefore focused on risk factor reduction. Previous population attributable risk estimates for western countries may have been underestimated as a result of the relatively low rates of midlife obesity and the lower weighting given to that variable in statistical models. Methods: Levin’s Attributable Risk which assumes independence of risk factors was used to calculate the proportion of dementia attributable to seven modifiable risk factors (midlife obesity, physical inactivity, smoking, low educational attainment, diabetes mellitus, midlife hypertension and depression) in Australia. Using a recently published modified formula and survey data from the Australia Diabetes, Obesity and Lifestyle Study, a more realistic population attributable risk estimate which accounts for non-independence of risk factors was calculated. Finally, the effect of a 5-20% reduction in each risk factor per decade on future dementia prevalence was computed. Results: Taking into consideration that risk factors do not operate independently, a more conservative estimate of 48.4% of dementia cases (117,294 of 242,500 cases) was found to be attributable to the seven modifiable lifestyle factors under study. We calculated that if each risk factor was to be reduced by 5%, 10%, 15% and 20% per decade, dementia prevalence would be reduced by between 1.6 and 7.2% in 2020, 3.3-14.9% in 2030, 4.9-22.8% in 2040 and 6.6-30.7% in 2050. Conclusion: Our largely theory-based findings suggest a strong case for greater investment in risk factor reduction programmes that target modifiable lifestyle factors, particularly increased engagement in physical activity. However, further data on risk factor treatment and dementia risk reduction from population-based studies are needed to investigate whether our estimates of potential dementia prevention are indeed realistic.

AB - Background: At present, dementia has no known cure. Interventions to delay onset and reduce prevalence of the disease are therefore focused on risk factor reduction. Previous population attributable risk estimates for western countries may have been underestimated as a result of the relatively low rates of midlife obesity and the lower weighting given to that variable in statistical models. Methods: Levin’s Attributable Risk which assumes independence of risk factors was used to calculate the proportion of dementia attributable to seven modifiable risk factors (midlife obesity, physical inactivity, smoking, low educational attainment, diabetes mellitus, midlife hypertension and depression) in Australia. Using a recently published modified formula and survey data from the Australia Diabetes, Obesity and Lifestyle Study, a more realistic population attributable risk estimate which accounts for non-independence of risk factors was calculated. Finally, the effect of a 5-20% reduction in each risk factor per decade on future dementia prevalence was computed. Results: Taking into consideration that risk factors do not operate independently, a more conservative estimate of 48.4% of dementia cases (117,294 of 242,500 cases) was found to be attributable to the seven modifiable lifestyle factors under study. We calculated that if each risk factor was to be reduced by 5%, 10%, 15% and 20% per decade, dementia prevalence would be reduced by between 1.6 and 7.2% in 2020, 3.3-14.9% in 2030, 4.9-22.8% in 2040 and 6.6-30.7% in 2050. Conclusion: Our largely theory-based findings suggest a strong case for greater investment in risk factor reduction programmes that target modifiable lifestyle factors, particularly increased engagement in physical activity. However, further data on risk factor treatment and dementia risk reduction from population-based studies are needed to investigate whether our estimates of potential dementia prevention are indeed realistic.

KW - Australia

KW - Dementia

KW - Population attributable risk

UR - http://www.scopus.com/inward/record.url?scp=85013053140&partnerID=8YFLogxK

U2 - 10.1186/s13195-017-0238-x

DO - 10.1186/s13195-017-0238-x

M3 - Article

VL - 9

JO - Alzheimer's Research and Therapy

JF - Alzheimer's Research and Therapy

SN - 1758-9193

IS - 1

M1 - 11

ER -