Tuesday May 14 2013
Is dementia caused by devices such as mobile phones?
'Technology, food additives and air pollution are causing people to develop dementia earlier than ever,' reports the Mail Online website. But this is a claim with little to no evidence to support it.
The study the Mail reports on looked at death rates in 10 developed countries, including the UK and the US. The researchers specifically focused on what they termed "neurological deaths". These are deaths arising from conditions that affect the brain and nervous system, such as motor neurone disease and dementia.
This study found that the overall death rate has fallen over the past 30 years. But levels of neurological deaths have risen significantly when comparing data from 2008-10 to comparative data from 1979-81.
It is not clear why there has been such a rise in the number of deaths from neurological disorders. The researchers speculate that the fact that people are living longer, there have been major improvements in diagnostic techniques, and significant changes in lifestyle and the environment – such as the increased use of food additives, more pollution, and new technologies such as wi-fi and mobile phones – could all contribute to the rising numbers.
It is the claim about modern technology that captured the Mail's imagination the most. But the key word here is "speculate": more research is needed to see whether factors such as "technology, food additives and air pollution" could be held responsible for the rise in neurological deaths.
Where did the story come from?
The study was carried out by researchers from Bournemouth University and Southampton University. There was no funding to declare. It was published in the peer-reviewed journal, Public Health.
This story was covered poorly by the Mail Online website. Speculation about the possible causes of the increase in deaths from neurological diseases was reported as fact.
What kind of research was this?
This was an observational study that aimed to see how total deaths (mortality) and deaths specifically from neurological causes in older adults (aged 55 to 74 years) varied between the periods 1979-81 and 2008-10 in 10 major developed countries (Australia, Canada, France, Germany, Italy, Japan, Netherlands, Spain, the UK and the US).
This type of study can tell us how death rates and deaths from neurological causes vary over time, but it cannot tell us why these rates vary.
In order to investigate whether any of the factors suggested by the Mail Online – such as electronic devices, food additives and air pollution – play a role, ideally a randomised controlled trial, or more likely a cohort study, would have to be performed.
Even these types of studies could be difficult to carry out. Given that certain technologies such as mobile phones are now a global phenomena, it would be hard to isolate a mobile-free control group.
What did the research involve?
The researchers compared World Health Organization (WHO) data on total mortality and deaths due to neurological causes in people aged between 55 and 74 years old for the period 1979-81 with data from 2008-10 (or for the latest years available) in 10 major developed countries.
Neurological deaths were analysed as a whole, or divided into "nervous disease deaths" and "Alzheimer's and other dementia deaths". Nervous disease deaths included deaths from various conditions where there was inflammation or degeneration of the nervous system, including multiple sclerosis, motor neurone disease and Parkinson's disease.
What were the basic results?
The researchers found that total mortality for people aged between 55 and 74 years old fell substantially in every country over the 30-year period. On average, there was a fall of 45% from 25,620 deaths per million men in 1979-81, to 14,158 deaths per million men in 2008-10. For women, there was a decrease of 54% from 13,591 deaths per million in 1971-81 compared with 6,195 deaths per million in 2008-10.
In contrast, in people aged between 55 and 74 years old deaths from neurological causes rose by at least 10% in men in seven countries, and in women in eight countries. Total neurological deaths for both women and men rose significantly in Australia, Canada, Germany, Italy, Spain, the UK and the US.
Total neurological deaths increased significantly only in women in the Netherlands. On average, there were 275 deaths per million due to neurological causes in men in 1979-81. This rose to 332 deaths per million in 2008-10, an increase of 21%. In women, there were 101 deaths per million due to neurological causes on average in 1971-81, rising to 260 deaths per million in 2008-10, an increase of 29%.
When deaths from nervous diseases and Alzheimer's and other dementias were considered separately:
- In men, deaths from nervous diseases rose from 144 deaths per million in 1979-81 to 203 deaths per million in 2008-10 on average across the 10 countries surveyed.
- Seven countries had at least 10% increases in death rates from nervous diseases in men. Rates fell by at least 10% in the other three countries.
- In women, deaths from nervous diseases rose from 104 deaths per million to 137 deaths per million on average. Six countries had at least 10% increases in the rate of death from nervous diseases in women. Rates fell by at least 10% in two other countries.
- In men, deaths from Alzheimer's and other dementias rose slightly from 128 deaths per million in 1979-81 to 130 deaths per million in 2008-10 on average. Death rates from Alzheimer's and other dementias rose by at least 10% in men in five countries, and fell by at least 10% in three countries.
- In women, deaths from Alzheimer's and other dementias rose from 86 deaths per million to 123 deaths per million on average.
- Death rates from Alzheimer's and other dementias rose by at least 10% in women in seven countries, and fell by at least 10% in two countries.
How did the researchers interpret the results?
The researchers conclude that in contrast to major reductions in general mortality, mortality due to neurological deaths has increased in the majority of the countries analysed. They state that, "These results pose a major public health problem".
The researchers go on to discuss potential explanations for the increase in neurological deaths seen, including:
- the fact that people are living longer, making it more likely that they will develop and possibly die from some of the diseases considered to be diseases of older people
- improved diagnostic techniques, allowing more diagnoses of neurological diseases to be made
- lifestyle or environmental factors, which may increase the risk of developing some of these diseases
This research has found that the death rate in people aged between 55 and 74 years old has fallen over the past 30 years in 10 developed countries (Australia, Canada, France, Germany, Italy, Japan, Netherlands, Spain, the UK and the USA). However, during this period deaths from neurological disorders such as Alzheimer's and other dementias (such as vascular dementia), Parkinson's disease and multiple sclerosis have increased on average.
The reasons for this increase in neurological deaths can only be speculated about. The researchers suggest that the fact that people are living longer, improvements in diagnostic techniques, and changes in lifestyle and the environment could contribute to the increase.
However, although this type of study can tell us how death rates and deaths from neurological causes are varying over time, it cannot tell us why these rates might be varying. More research is required to see whether factors such as "technology, food additives and air pollution" really are responsible for the increase in death rates due to neurological disorders.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.