Determinants of neurological disease: Synthesis of systematic reviews

- With population aging, the burden of neurological disease is increasing worldwide.
- Understanding the factors affecting the onset and progression of neurological disease through systematic review is essential for the development of strategies to reduce the burden of these diseases.
- Systematic review identified biological, demographic, environmental, genetic, lifestyle and pharmacological risk factors for specific neurological conditions.
- Several risk factors were associated with the onset of multiple conditions. Pesticides, for example, were associated with an increased risk of Alzheimer's disease, amyotrophic lateral sclerosis, primary brain tumours, and Parkinson's disease.
- Helmet use was associated with a reduction in onset of neurotrauma, as well as all neurologic conditions for which head injury was a risk factor.
- The findings presented here should be viewed as provisional, pending a more in-depth evaluation of the weight of evidence.
- Further research will also serve to fill current data gaps, particularly regarding risk factors for the progression of neurological disease.
- In the interim, the modifiable risk factors may be considered as potential candidates for the development of targeted interventions to reduce the burden of neurological disease in Canada and internationally.

Systematic reviews were conducted to identify risk factors associated with the onset and progression of 14 neurological conditions, prioritized as a component of the National Population Health Study of Neurological Conditions. These systematic reviews provided a basis for evaluating the weight of evidence of evidence for risk factors for the onset and progression of the 14 individual neurological conditions considered. A number of risk factors associated with an increased risk of onset for more than one condition, including exposure to pesticides (associated with an increased risk of AD, amyotrophic lateral sclerosis, brain tumours, and PD; smoking (AD, MS); and infection (MS, Tourette syndrome). Coffee and tea intake was associated with a decreased risk of onset of both dystonia and PD. Further understanding of the etiology of priority neurological conditions will be helpful in focusing future research initiatives and in the development of interventions to reduce the burden associated with neurological conditions in Canada and internationally.