The increased life expectancy of the global population is well established, but the quality of life among the world’s growing population of older adults is less understood. Is an older population an inevitably unhealthier, less cognitively functional one? Do longer lifespans just mean that people are spending more years in poor health, or can quality of life be extended along with life expectancy? A new study in Denmark suggests that a rise in life expectancy may bring with it a rise in cognitively healthy years.
Published in the Lancet, the article reports on the cognitive and physical well-being of two cohorts of Danes age 90 and better: those born in 1905 (who were studied in 1998), and those born in 1915 (studied in 2010). Because the State of Denmark maintains a national registry of all individuals, the investigators were able to identify all Danes born during those years still living in Denmark, and solicited the participation of the entire cohort of those born in the years 1905 and 1915.
Unlike many studies that are based on a smaller sample of a large population, researchers for this study solicited all individuals in the target population (i.e. the two birth year cohorts), regardless of health status, type of residence (such as nursing homes), or cognitive ability. For each cohort, researchers were able to recruit over 60 percent of the national population, administering interviews, physical tests, and cognitive tests, as well as collecting blood or saliva. Participants in each cohort were given the same assessments, 12 years apart. The researchers then compared both of the age cohorts (divided for analysis by sex) on a variety of physical and cognitive measures of well-being.
Danes born in 1915 had a greater chance of surviving into their 90s than those in the 1905 cohort. While the 1915 cohort were, on average, just over two years older than the 1905 cohort when tested (being tested just over 12 years later), the 1915 cohort performed significantly better on measures of cognitive function and daily functional well-being. There were no significant differences in physical strength or gait speed, or on depressive symptoms. It remains to be seen whether these findings will be replicated in other birth cohorts or other nations. If these findings do reflect a more general global pattern, however, it is possible that the care needs of future cohorts of older adults will be less than currently expected.
Christensen K, Thinggaard M, Oksuzyan A, et al. Physical and cognitive function of people older than 90 years: a comparison of two Danish cohorts born 10 years apart. The Lancet. (2013). DOI: 10.1016/S0140-6736(13)60777-1