A very natural response to receiving a diagnosis of MND is to ask ‘Why me?’. Many people with the disease question whether their MND could have been caused by something in their environment, their occupation or a lifestyle factor such as smoking, diet or exercise.
The study of environmental and lifestyle factors that may predispose people to disease is known as epidemiology. Sporadic MND is thought to result from the cumulative effects of numerous risk factors, in people whose overall genetic make-up makes their motor neurones particularly vulnerable to damage. The identification of these risk factors could provide insight into the abnormal mechanisms underlying the development of the disease and eventually aid in disease prevention.
The trouble is, identifying these factors with any certainty is extremely difficult. In this session’s opening presentation, Ettore Beghi from Milan discussed why studies that aim to assess environmental and lifestyle contributors consistently fail to generate conclusive evidence. For instance, studies on heavy metal exposure, diet, head trauma and statin use were concluded as not having enough reliable evidence to suggest a possible risk. He did however note, that it is unlikely that statin use increases the risk of somebody developing MND as he said that “despite a 10 fold increase in statin use (in recent years), there has not been the same pattern for cases of ALS”.
He also suggested that researchers need to bear certain key considerations in mind when designing epidemiological studies, including how they select their study participants and how they should be unbias when defining the risk factors themselves.
The remaining talks in this session gave examples of how registers of people with MND in a particular country or region can be used to glean information about various aspects of the disease.
Marc Huisman described how a register of people with MND in the Netherlands has allowed him and his colleagues to investigate possible occupational risk factors. To date, these include an increased risk for farmers and electricians. They also identified (in smaller numbers and so this evidence is less reliable) that dental assistants have an increased risk, whereas general managers have a decreased risk. Their next steps are to ascertain what underlying exposures may be linked to these jobs to increase, or decrease the risk of somebody developing MND. The Dutch register also suggested that a family history of other neurodegenerative diseases may increase risk of MND, while a family history of cardiovascular disease may reduce risk.
There are still a number of questions regarding lifestyle and environmental causes that need to be answered. But, if researchers can collect reliable evidence, then the research community will be in a better position to start asking why (instead of what) particular risk factors can contribute to the cause of MND.