hile we are still finding new risk genes, genetics alone cannot for the 98% of sporadic cases of late-onset Alzheimer’s disease. As scientists we believe that the risk of developing Alzheimer’s comes from a combination of genetics, lifestyle and environmental factors, rather than a single cause.
There are certain environmental factors that are suspected to increase the risk of developing Alzheimer’s, with some studies showing a link to air pollution from car exhaust fumes, for example. The potential risk from environmental factors for developing Alzheimer’s and other chronic diseases, has always interested me. Long before I became an Alzheimer’s scientist, I questioned for example, the impact of the industrial chemicals that find their way into our waterways, air supply, food sources, and ultimately into our own body tissue. What effect did their bioaccumulation have on our health?
Indeed, the effects of exposure to inorganic and organic hazards, pesticides, industrial chemicals such as flame retardants and air pollutants on our health has been under investigation through epidemiological studies for many years. Studies have for example looked at how these exposures affect a growing foetus in utero, and after birth during a child’s growth and development through into adulthood, to try and understand how it could potentially increase the risk of Alzheimer’s in later life.
Chemical exposure is just one of a range of very diverse environmental factors. Broadly speaking, environmental factors are anything that affects living organisms. Examples therefore include diet, exposure to toxins, pathogens, radiation, chemicals found in personal-care products and household cleaners, stress and even mental and physical abuse. All these factors could in isolation or through bioaccumulation act as a trigger to develop disease.
With the overwhelming diversity of different types of environmental factors, how do any of these factors actually have a systemic impact on our health? I briefly touched on the field of epigenetics in the section on Genetic Risk Factors. Our epigenome, which controls our genome (our genetic blueprint) through an epigenetic process called DNA methylation, telling our genes to become either active or inactive in their role of protein formation – the building blocks for our bodies. Methyl groups are added to our DNA molecules through this process, which instead of changing the DNA sequence itself, only changes how it is expressed.
This epigenetic programming of our genes is strongly affected by environmental factors such as food, drugs and our exposure to chemical toxins that cause epigenetic changes by altering the way the methylation process occurs. There is extensive research effort going into understanding this process of how environmental exposure influences our epigenetic regulation and its flow on effect and risk factor for diseases such as Alzheimer’s.
The following papers give you a taster of some studies that investigate the impact of environmental factors and the epigenomics of Alzheimer’s:
- Pelcovits, A, et.al. (2015). Simultaneous Onset of Alzheimer’s Disease in a Husband and Wife in Their Mid-Fifties: What Do We Really Know About Environmental Factors? The Open Neurology Journal, 9, 1–3
- Wainaina, M. N, et.al (2014). Environmental factors in the development and progression of late-onset Alzheimer’s disease. Neuroscience Bulletin, 30(2), 253–270
- Bennett, D. A, et.al (2015). Epigenomics of Alzheimer’s Disease. Translational Research?: The Journal of Laboratory and Clinical Medicine, 165(1), 200–220. http://doi.org/10.1016/j.trsl.2014.05.006
- Killin LOJ, et.al. Environmental risk factors for dementia: a systematic review. BMC Geriatrics. 2016;16:175.
Reduce eating processed foods that contain chemicals known to be a health risk such as nitrates in preserved meats, and high sugar content that has been linked to poor cognitive function
Use natural household cleaning products such as baking soda and white vinegar
Quit smoking if you are already a smoker
Avoid chemical exposure in the home and workplace through use of protective clothing such as the correct gloves and dust masks
Seek medical advice for ongoing infection or exposure to any pathogens.