How will the state of health for humankind change in 20 to 50 years in the future, and in what direction will it be headed? Is it possible to change its course for the better?
Facing the very difficult task of predicting large trends in society more than 20 years into the future, it appears that the most accurate estimates are for the increase in global human population, aging of the population in developed countries, and in Japan, fewer number of children and the trend towards a super-aged society (it is forecast that in the year 2050, two-fifths of the population will be over the age of 65). These statistics are based on the composition of the current population and biological characteristics of the human species as a large mammal (i.e. limitations on life duration and number of offspring per litter), and are aligned with bigger trends in society around the world, such as health and hygienic conditions and birth rate.
On the other hand, concentration of populations in urban areas is occurring around the globe, with the trend especially prominent in Asia. In the past, there were more people living in rural areas than the city, but the balance tipped in 2009, and it is estimated that by 2050, the number of urban inhabitants will be double the number of those living in the countryside. The reason may well be that people living today, especially the younger generation who will become the main contributors to future increase in population, wish to live in the city where it is more hygienic and earning levels are high, and do not want to live in the countryside. Aesop's "Town Mouse and Country Mouse" is very much a notion of the past, and unless there is a new factor that comes into play, this trend is likely to continue into the future.
With this background, it is believed that infectious diseases that were once the major threat to human beings are being replaced with mental diseases, including dementia and depression, and that they are the likely candidates to make the top of the list of illnesses that will have the most affect on people's health in the future.
Ironically, the biggest contributing factor to the increase in dementia is increased lifespan. There is still no cure for the most well-known form of dementia, Alzheimer's disease (AD). For non-hereditary AD, which constitutes 99% of all cases of the disease, most patients show signs of dementia after the age of 65. In Japan, where average life span did not reach 65 years of age up to the mid 1950s, most people had already ended their lives before the age at which the disease develops.
For depression, there has been a meta-analysis* report showing that morbidity prevalence rate is 39% higher in large cities than rural areas, and as the concentration of population in cities continues, the increase in number of patients of depression is expected to continue growing. However, it is the opinion of many psychiatrists that the dramatic increase of depressed patients in Japan over the past 10 years is not due to an increase in cases of traditional "depression," but to a large increase in cases that have come to be categorized in Japan as the so-called "new type depression." The definition of "depression" itself is being debated, and aside from the traditional diagnostic process consisting of a patient interview, it is anticipated that biological markers will also be added to the diagnostic standard.
In the next 20 years, is it possible to change the way we treat illnesses that erode 'memory,' the very foundation of an individual, and illnesses related to 'mood,' which is critical to individuals but difficult to evaluate objectively? How about in 50 years? This is an extremely difficult but important issue, and one that is very much worth pursuing.
* meta-analysis: method of analysis in which data from multiple clinical studies conducted independently in the past are collected and integrated, and then analyzed using statistical methods.