Medical Challenges of Improving the Quality of a Longer Life

WHEN GERIATRICIANS AND GERONTOLOGIST REsearchers consider the health challenges that will affect the global population in coming decades, their reactions most often combine alarm with a determination for action. Based on current demographic forecasts and the age-incidence patterns of major age-related diseases, the prospects for greatly increased prevalence of age-related frailty and disability can even induce despair. However, in addition to the continuing trend toward increased life expectancy, emerging indications, informed by recent scientific advances, suggest that some of the more daunting challenges might be met by a preventive life-course perspective that extends from conception through extreme old age. The 6.5 billion inhabitants of the world currently include a “bulge” generation, which, although presently of working age, will in 3 to 4 decades become old. By 2050, the world’s population is expected to be 9.1 billion, and the great heterogeneity in growth rates means that the population in the developed world will remain relatively stable while the populations of the 50 least-developed countries are expected to more than double over the same time period. By 2050, individuals aged 60 years and older are expected to represent at least a quarter of the world’s population, and 3 of 4 persons in the group aged 80 years or older will be living in the developing world. In parallel with the shifting balance of generations, the incidence and prevalence of chronic diseases are expected to reach unprecedented levels. It is estimated, for example, that by 2050 there will be more than 4.5 million hip fractures annually and more than 36 million patients with dementia. The increases in the numbers affected by these 2 profoundly disabling conditions help explain the concerns of an imminent pandemic of frailty, comorbidity, and disability. These alarming forecasts are often presented as if old age is a separate phase of life. However, advancing knowledge of the longer-term implications on subsequent clinical outcomes of physical and social exposure during gestation, childhood, and young and mid adulthood emphasizes how health should be considered with a life-course perspective from conception to extreme old age. This message is underscored by increasing understanding of the biological processes responsible for intrinsic aging, which results from the gradual, lifelong accumulation of molecular and cellular damage. A wealth of experimental data indicates that the damage that will eventually give rise to adverse health outcomes in old age is accumulating from the earliest stages of life. This raises the exciting prospect that if medical and social interventions can be identified that reduce the rate of damage accumulation, it may be possible to exploit the intrinsic malleability of the aging process. Such malleability is revealed not only in animal models but also by the fact that in recent decades the continuing increase in life expectancy in developed countries is driven by an entirely new phenomenon: the declining mortality of the old. Within this perspective, the prevention of age-related frailty (a vulnerable status preceding the onset of overt disability) and of age-related disability (which may be linked either to aging or chronic conditions associated with age) could begin at any age. Targeted strategies that have the potential to lead to healthy old age include reducing frailty and agerelated disability, but also addressing disease-associated disability and identifying (and intervening on) those at risk in the earlier stages of life.