Older Persons in The Netherlands and the United States: Similar in Trends in Life in Good Cognitive Health and Different in Trends in Life Without Disability/Poor Health

Is there good news or bad news about trends in health in the aging population of the Netherlands? It seems that there is both good and bad news, as trends in healthy life expectancy in the Netherlands differ depending on whether cognitive or physical health is the focus of study. In this issue, Deeg et al. (p. 1652) report increases in total life expectancy and cognitively healthy life expectancy and decreases in cognitively impaired life expectancy in the Netherlands over a 23-year study period; life expectancy in good physical health declined during the same period, and life expectancy in poor physical health increased. These results were based on the Longitudinal Aging Study Amsterdam, a valuable long-running, population-representative study that has provided significant trend data on health in the Netherlands.

ARE THESE RESULTS BELIEVABLE?

Does it make sense that as mortality declines and life expectancy increases, healthy physical life expectancy does not increase? First, there is no reason to question the validity of the Deeg et al. results; the study was methodologically well conducted and based on a valid data source. Second, the results match those of other studies and make theoretical sense. A decline or lack of increase in the proportion of people living physically healthy lives has been recorded in a number of countries. There are many reasons this is possible.

Mortality declines tend to occur because people who are sick and disabled do not die, not because people without disease and disability do not die. This means that there are more people with health problems than there would have been if mortality rates had not decreased, and the length and proportion of healthy life expectancy may decrease (or at least not increase). This seemingly adverse trend results from success in extending life, which is a major aim of the medical care provided to elderly individuals. Many measures of physical health can be used in studies of trends, and their links to mortality can vary and affect the trends observed.

Increases in cognitively healthy life expectancy as well as decreases in the prevalence of dementia have been reported in a number of countries. To date they have not been juxtaposed, as reported by Deeg et al. for the Netherlands, and it is quite useful to see this different direction of change over the same period. How can it be that cognitively healthy life expectancy increases at the same time as physical health deteriorates or does not improve?

Cognitive functioning at older ages may be determined more by circumstances at younger ages than is physical functioning. Whether an elderly individual drops below the line dividing good and bad cognition according to a test depends on the maximum level of cognitive functioning achieved in young adulthood as well as the rate of decline with age. Thus, it is possible that different life circumstances affect trends in cognitive life expectancy and physical health. It may be that cognitive life expectancy is more sensitive to early life conditions and that physical life expectancy is more sensitive to later conditions.

COMPARISON WITH THE UNITED STATES

Two recent US studies provide a rough comparison with the figures from the Netherlands in terms of changes in the percentage of life expectancy above the age of 65 years spent in good cognitive health and without disability.^1,2 Because definitions of good health and cognition differed between the studies, as did the lengths of observation, it is useful to compare annual changes in the percentage of life expectancy without disability in the United States and the percentage of life expectancy not in poor health in the Netherlands, along with changes per year in the percentage of life expectancy with good cognitive functioning (Table 1).

TABLE 1—

Comparisons Between the Netherlands and the United States in Different Components of Life Expectancy: 1990–2016

	United States					Netherlands
Variable	1990	2000	2010	Change per Annum, Years	Change per Annum, %	1993	2016	Change per Annum, Years	Change per Annum, %
Men
Total LE at 65 y	15.1	16.1	17.7	+0.11		14.7	18.7	+0.17
LE without disability/not in poor health, %	49.1		53.5		+0.18	87.7	84.3		−0.15
LE with good cognition, %		66.5	70.6		+0.41	74.8	83.7		+0.39
Women
Total LE at 65 y	19.0	19.1	20.3	+0.06		19.2	21.4	+0.10
LE without disability/not in poor health, %	52.0		56.7		+0.24	61.7	61.1		−0.03
LE with good cognition, %		65.4	69.5		+0.59	69.9	84.4		+0.63

Note. LE = life expectancy. Data were derived from Deeg et al. (p. 1652) and Crimmins et al.^1,2

Table 1 shows that the percentage of life expectancy spent without disability increases modestly in the United States among both men and women over the 20-year period between 1990 and 2010 (by 0.18% and 0.24% per year). The declines in the percentage of life expectancy not in poor health in the Netherlands from 1993 to 2016 indicate a change in the opposite direction, although the decline was small among women (0.03%, as compared with 0.15% among men). The definitions of physical health used in the two studies are quite different, which may be one cause of the differences in the directions of the trends.

Annual increases in the percentage of life expectancy with good cognitive health are very similar in the two countries: 0.41% in the United States and 0.39% in the Netherlands among men and 0.59% in the United States and 0.63% in the Netherlands among women. In both the Netherlands (as reported by Deeg et al.) and the United States,³ it is estimated that about half of the rise in life expectancy with good cognition has resulted from increases in educational levels in older cohorts. These increases in education have improved the cognitive abilities of members of successive cohorts across the age range. At younger ages, this improvement in cognitive functioning over time has been recognized as the “Flynn effect.”⁴ However, these early life changes seem not to have improved the physical functioning of the older population in the same way as cognitive functioning.

VALUE OF INTERNATIONAL COMPARISONS

International comparisons are useful for understanding how macro-level trends in health and varying policies and practices can lead to different situations across countries. Such comparisons can also help in assessing the reliability and validity of health trends observed in individual countries. A recent National Academy of Sciences report on US life expectancy stagnation employed this approach in an investigation of how trends and health-affecting conditions in the United States compared with those in other countries.⁵ Although most of the countries included in the analysis have not experienced the stagnation that has occurred over recent decades in the United States, two have faced similar situations: Denmark and the Netherlands.

At the same time the topic of mortality stagnation arose in the United States, it became a topic of research and resulting policy change in the Netherlands, leading to increases in health care availability and use among the older population. This situation has been credited with ending mortality stagnation and leading to a faster rate of increase in life expectancy among the elderly population.⁶ Whereas the Netherlands has increased its rate of gains in life expectancy, the United States has not, and it has continued to fall behind peer countries.³ The data in Table 1 show that annual increases in life expectancy at the age of 65 years in the Netherlands during the period assessed exceeded those of the United States by about 55% among men and 66% among women.

Strangely, it is possible that the rapid decrease in mortality in the Netherlands has adversely affected the physical health status of the country’s population. The reason is that the rapid mortality decline was likely achieved by keeping people with illnesses and disabilities alive rather than keeping well people alive. The growing availability of data on which to base international comparisons is important in understanding changes in health across countries and the complexity of such changes within populations.