The importance of knowing life expectancy

Predicting life expectancy is far from an exact science. Statistical modeling may be mathematically precise, but assumptions are far more subjective. A 2009 study confidently stated that most babies born in the U.S. and Western Europe today should live to 100. Another group of scientists predicts life expectancy at birth will be 100 years by 2060, based on current trends. A more modest projection by the United Nations arrived at the same figure by the year 2300.

On the other hand, an influential article in the New England Journal of Medicine estimated that the effect of obesity could trim as much as five years of life by the middle of this century.

Other research echoes this. Researchers used a forecasting method that accounts for the delayed effects of accumulated health risks among younger adults. The results suggested the effects of rising obesity on future life expectancy and health-care costs could be far worse than currently anticipated.

Projecting life expectancy is much more than an academic exercise. If it is underestimated by just one year, that would mean an extra 53 million years lived by Americans 65 and older between 2000 and 2050. That would have enormous implications for Medicare and Social Security costs.

If life expectancy continues to grow and disease is kept at bay, life stages – education, work, retirement – will continue to be blurred.  Young people are taking longer to complete higher education because of steeply rising costs and dim career prospects. Meanwhile, the elderly are delaying retirement because of eroded stock portfolios, the security of health-insurance benefits in the workplace or self-fulfillment – especially if they are in robust health.

One trend is clear: The world is going gray. The number of people 65 and older will double to 1.3 billion globally by 2040. The elderly will outnumber children under age 5 for the first time in history.

At this point, there is no technology to extend the human lifespan. Dr. Nortin Hadler, in his book Worried Sick: A Prescription for Health in an Overtreated America, contends that the best we can hope for is 85 disease-free years – at which point life’s warranty expires. Any time beyond that is a bonus. He argues that medicine has little impact on longevity because it saves the lives of only a small percentage of the population.

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