An examination of human life expectancy in different countries, communities or ethnic groups offers both useful insights and conundrums about the factors that affect how long people may typically live. Life expectancy is based on the expected number of years of life remaining at a given age. Historical data based on life expectancy at birth may be misleading because of the infant mortality rates. If a person survived to young adulthood their residual life expectancy from that point forward could more than double. Though infant mortality has dropped hugely in the 20th century due to an improvement in public health measures, there are many poor countries where data may still be distorted in this way. Plus pandemics like influenza, the plague or AIDS have and continue to distort expectancy statistics.
Life expectancy needs to be distinguished from “lifespan” which is a measure of the maximum length a species can live based on optimal circumstances. Thus the lifespan of human species is generally thought to be 120 years while the average life expectancy of, say, an Asian-American is 87, ten years longer than their Euro-American counterpart – a trend reflected globally. The cozy consensus that once accepted 120 years as being the approximate limit of our species is, however, being challenged today by scientists who either believe it is closer to 150 or who believe there is no potential limit at all. In terms of relevance to the theme of this book, the idea is to nudge our personal life expectancy closer towards our natural lifespan. More precisely it is to nudge our healthy, joyous, “dependency-free” life expectancy towards that goal.
The main determinants for life expectancy today are thought to be an amalgam of heredity (genes), income, diet, culture, education, occupation, environment and motivation. Someone born into an educated, cohesive family with enough money to eat a decent nutritious diet, living in a pollution free environment or body with a stimulating job, few financial or other worries, and having a disciplined and motivated lifestyle will typically live significantly longer than those without these factors present. In Glasgow, Scotland the male life expectancy gap between a prosperous area called lionize and a deprived one called Calton only five miles away is 28 years. A conundrum is that neither access to medical care nor real poverty is the issue as public health and a welfare safety net is freely and readily available to people in both areas.
Possibly it suggests a new phenomenon alarming the medical community worldwide. Life expectancy, for so long forging ahead in affluent nations, is beginning to falter or even fall in areas due to the alarming rise of junk-food diets (convenience food) and sedentary lifestyles (lack of exercise). Often linked with smoking, alcohol consumption and stress, this sets in motion a downward spiral of health problems ironically termed “diseases of affluence" which, in turn, provoke the early onset of...