Frailty and multimorbidity

Most of the life expectancy still to be gained in high-income countries lies at the oldest ages, and those are the ages the data describe worst. Since 2010, mortality above 85 has improved more slowly than mortality at 65 in most countries. Above 95 it is barely measured. Ages are misreported, and populations between censuses are estimated rather than counted. Centenarians, whose numbers double every decade, are validated in a few countries and assumed in the rest.

Two families of tools measure health at those ages. Frailty is a loss of reserve, scored from deficits or from physical performance. It predicts death and hospital admission better than age does, and some health systems now record it routinely. Multimorbidity, the presence of several long-term conditions, is the norm above 75. It begins a decade or more earlier in deprived areas than in affluent ones. Both are rising in prevalence, because more people reach the ages at which they occur. Whether they are rising at a given age differs by country and by measure, and depends on whether the condition is diagnosed more or present more. That is the difference between morbidity compressed into fewer years and morbidity spread across more.

The best evidence comes from the countries that can follow a whole population. Denmark, Sweden and the Netherlands do so from registers. Japan, which has the largest and best-measured oldest-old population in the world, does so from surveys. Elsewhere the oldest ages are studied through cohorts that under-represent the frail, those living in institutions and the poor.

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