Brain disorders, including developmental, psychiatric and neurodegenerative diseases, represent an enormous disease burden, in terms of human suffering and economic cost.
Many brain disorders are chronic and incurable conditions whose disabling effects may continue for years or even decades. Thus, the overall disease burden from these disorders is much greater than would be suggested by mortality figures alone. The extent of this burden is underlined by data from the World Health Organization. To compare the impact of different diseases, the WHO estimates for each disease category the "Disability Adjusted Life Years" or DALYs -- years of healthy life that are lost to disability as well as death. Each disease is assigned a weighting factor according to the severity of the resulting disability.
On this measure, brain disorders emerge as leading contributors to global disease burden; for example, according to the most recent (2004) WHO survey, unipolar depressive disorders are the single biggest source of lost DALYs in the high income countries, and the third biggest worldwide. In Europe it has been estimated that 35% of all disease burden is attributable to brain disorders.
The economic costs of brain disorders are correspondingly large. These include not only the cost of treatment, but also the lost productivity of patients and their caregivers, for whom looking after chronically disabled family members can represent an enormous source of emotional, practical, and financial burden. In Europe, for example, the total cost of brain disorders was estimated to be (L386 billion per year in 2004 prices (including direct costs of treatment and care plus indirect cost of lost workdays and lost productivity) -- twice the estimated cost of cancer. A more recent survey from the same group (including a wider range of disorders and costs, plus new EU member countries) estimated the total cost in 2010 to be (L)798 billion, of which 60% was attributable to direct costs and 40% to lost productivity.
Some specific examples are discussed in more detail below. (Costs are quoted as originally reported and are not adjusted for inflation.)
Psychiatric Illness -- The U.S. National Institute of Mental Health (NIMH) estimates that about 1 in 4 American adults suffer from a diagnosable mental disorder in any given year, with nearly 6% suffering serious disabilities as a result.
The WHO estimates that unipolar depression is the third leading causes of disease burden worldwide, (after lower respiratory infections and diarrheal diseases), and the number one cause in the high-income countries.
In addition to the human suffering they cause, psychiatric disorders are among the most expensive of all health problems. A US government study, the National Comorbidity Study Replication, estimated that serious mental illness accounted for $193 billion in lost earnings (based on data from 2002). Independently, the Milken Institute estimated in 2007 that mental illness accounted for $171 billion in lost economic output (based on 2003 data).
In a commentary accompanying the US government study, the director of National Institute for Mental Health, Thomas Insel, estimated that the total cost of serious mental illness in the US exceeds $317 billion per year. These costs include the estimated $193 billion in lost earnings plus $100 billion per year in direct health care costs and another $24 billion in disability benefits.
Insel emphasizes that this is a conservative estimate that does not take account of such factors as homelessness, incarceration, substance abuse or cigarette smoking, all of which are associated with mental illness. The US National Bureau of Economic Research has estimated that 38 percent of all alcohol, 44 percent of all cocaine, and 40 percent of all cigarettes are consumed by people with an existing mental illness.
Alzheimer’s Disease -- In its 2011 annual report, the Alzheimer’s Association (AA) estimates that 5.4 million people in the US have Alzheimer’s disease (AD). The risk of AD increases with age, so unless new treatments are discovered this number will grow sharply as the baby boomer generation reaches old age. By 2050, the AA estimates that between 11 million and 16 million Americans will have the disease, with one new case appearing every 33 seconds.
Alzheimer’s and other dementias have a disproportionate impact on countries with longer life expectancies, and represent the fourth highest source of overall disease burden in the high-income countries, according to WHO statistics. But the disease is also a major burden in less wealthy countries and is expected to grow rapidly. Worldwide, Alheimers Disease International (ADI) estimates in its 2010 report that there are 35.6 million people with AD worldwide as of 2010, and that this will grow to 115.4 million people by 2050.
The economic cost of AD is already enormous, and is expected to grow rapidly as more people live to a greater age with more serious impairments. Worldwide, ADI estimates that for 2010 the global cost of dementia (of which Alzheimer's is the major cause), including medical costs and cost of formal and informal care, is $604 billion -- about 1% of world gross domestic product. The costs are disproportionatetly high in wealthy countries. In the US, for example, the Alzheimer’s Association estimates that the cost of providing care for AD patients is $183 billion per year, as of 2011. If present trends continue, this cost is projected to grow to $1.1 trillion per year (in 2011 dollars) by 2050 – an overwhelming economic burden.
Parkinson’s Disease -- The U.S. National Institute for Neurological Disorders and Stroke (NINDS) estimated in a 2006 report that about 50,000 new cases of Parkinson's disease are diagnosed in the US each year, and the total number of cases in the US is at least 500,000. The true prevalence (total number of cases) of Parkinson’s disease is difficult to assess, because the disease is typically not diagnosed until the disease process is already far advanced. Therefore the actual number of Americans with the disease is almost certainly higher than the diagnostic numbers would suggest.
Worldwide numbers are difficult to obtain, but in industrialized countries the prevalence of Parkinson's disease is about 1% for people over 60, with estimates of up to 4% for people in the highest age groups (de Lau & Breteler 2006). The risk of developing Parkinson's disease rises sharply with age after the age of 60, so the number of cases is likely to grow significantly as populations become older throughout the world. In the US, for example, Dorsey et al (2007) estimated that the prevalence will at least double by 2030.
According to the 2006 report referenced above, NINDS estimates that the economic cost of Parkinson's disease in the US exceeds $6 billion per year. This figure may be conservative; other estimates are much higher, particularly when indirect costs such as lost productivity are also included. For example, Huse et al (2005) estimated a cost to the US economy of $23 billion per year (in 2002 dollars) and O’Brien et al (2009) estimated the total cost at $10.78 billion per year or $21,626 per patient per year (in 2007 dollars). In Europe, Gustavsson et al (2011) estimated the 2010 cost of Parkinson's disease to be €13.9 billion.
Autism Spectrum Disorders -- Autism and Autism Spectrum Disorders are now estimated to affect 1 in 88 children living in the US, according to a 2012 report from the Centers for Disease Control. The number of diagnosed cases has increased sharply in recent years, but it is still unclear to what extent this reflects changing patterns of diagnosis rather than actual increases in the incidence of the disorder. Although comprehensive global statics are not available, similar estimates have emerged from other countries. For example, the UK National Health Service estimates the prevalence of Autism Spectrum disorders among adults in England is approximately one percent. A 2011 study of a South Korean population yielded an even higher number, about 1 in 38 children, suggesting that better screening methods might lead to subtantially higher estimates of global prevalence in the future.
Autism is often depicted as a disorder of childhood, but it is in fact a lifelong condition and the economic costs of autism also continue throughout life. The economic cost to the U.S. was estimated at $35 billion per year, including the direct costs of care and the indirect costs of lost productivity for the affected individuals and for their caregivers. Much of the estimated $3.2 million lifetime cost per case is attributable to the cost of adult care and to lost productivity during adult life.