In this lecture, we are going to review some special differences in health. Let me start by taking a look at the figures that characterize aging in contemporary global societies. The world is getting older. The median age of humanity is about 30 years, six years more than in 1950. The number of older people is constantly increasing. Only six percent of humanity was aged 65 or over in 1990. In 2050, we'll be and I include myself in this number, 16 percent. Population aging at a global scale is the result of two major trends. The first one is called 'aging from the top'. Life expectancy has more than doubled since 1900. In 1950 on average, a human being could expect to live 46 years. A baby born today can expect to live more than 77 years. This is an incredible step forward and a tremendous leap in human history. It is explained by a combination of factors, all of which are linked to each other, advances in medicine, economic development, the evolution of social and cultural norms, urbanization and improved living conditions, healthy behaviors. The second underlying trend is 'aging from the bottom'. Fertility levels are constantly decreasing. In many Western countries, the average number of children per woman has fallen below 1.5. Data from the World Bank indicates that in middle income countries it is now 2.3 and in low income countries it has decreased from 6.4 in 1990 to 4.6 in 2018, and it is expected to drop further. However, this development is not homogeneous. Japan, Germany, Greece, Italy, Portugal make up the top five, with more than 20 percent of people aged 65 or over, according to the United Nations. Elsewhere, such as in South America, Africa and a large part of Asia, the population is still relatively young, but the process is already underway. For example, the average age in countries like Brazil or Tunisia has increased from 25 to 33 in the last 20 years. Also, there are differences between urban and rural areas. Demographic aging is often associated with demographic decline of low density territories. Many young adults in rural areas move to urban centers to seek opportunities from areas that already face challenges related to depopulation, economic decline, poverty and reduced services provision. However, low density territories are not the only ones facing a population aging process. This is now also the case of urban areas, with growing numbers of older adults living in central areas, suburbs and informal settlements. Over the past 30 years, the number of people aged 65 and over living in urban areas has more than doubled, increasing from 160 million to 355 million worldwide, a 121 percent increase, while the total population increased 46 percent. Currently, nearly two-thirds of older people live in urban areas, compared to less than half in 1990. These trends raise a number of major challenges in our urban areas, in particular how to ensure good conditions for healthy aging. One fundamental point is the role of place. Places shape our opportunities, our exposure to risk factors, our choices and behaviors, places can be stressful and contribute to mental health issues. They can be more or less exposed to a number of pollutants. The availability and design of public space and infrastructure influences our possibilities and motivation to be physically active. It's not just a question of biology or genetics. It's not just a question of health care services. It is also a question of the qualities of the environments where we are located. Health conditions vary between continents. Life expectancy at age 60, for example, is a measure of the number of years a person who has reached the age of 60 can expect to live. According to the World Health Organization, it is only 13 years in Lesotho, it doesn't reach 17 years in Botswana, Congo, Gambia and Burundi. It doesn't reach 20 years in Azerbaijan, in Myanmar or in Bolivia. It is 24 in Belgium, 25 in Canada, 26 in Japan. Health conditions in countries belonging to the same continent also differ. In Europe, for example, life expectancy at age 60 exceeds 24 years in some countries such as Germany, Norway or France, but doesn't reach 20 years in Bulgaria. Differences are driven by discrepancies in economic developments, education, health care services, social and labour conditions, lifestyle and the local environments. Differences are also expressed within countries between the various regions that make them up. In the UK, for instance, health life expectancy is lower where material deprivation is higher. This is particularly apparent in the north of England. Differences don't stop on the regional scale. The living conditions are different between the various districts of a city, which partly explains the local differences in life expectancy at birth. It is now widely recognized that your zip codes can be a more reliable determinants of health than your genetic code. For example, over a distance of only eight kilometres across the metro line, Lisbon life expectancy for those born in Sao Domingos de Benfica is 80.7 years. While a person living in the Santa Maria Maior neighborhood will on average leave 74.5. As you can see, there are great differences in health between locations. Where we grow, live, work and retire has high impacts on our health and well-being and our expected healthy life years.