Linguistic Ability in Early Life and Longevity: Findings from the Nun Study

Abstract

Findings from the Nun Study indicate that low linguistic ability in early life has a strong relationship to poor cognitive function and dementia in late life and to the number of Alzheimer’s disease lesions in the brain. In the present analyses, we investigated the relationship between linguistic ability in early life and all cause mortality in late life in a subset of 180 participants in the Nun Study. Two measures of linguistic ability in early life - idea (proposition) density and grammatical complexity - were derived from autobiographies written by the participants when they were 18 to 32 years old. An average of 58 years later, when these participants were 75 to 93 years old, all cause mortality rates were determined. Of the two linguistic measures, idea density in early life had the strongest and most consistent relationship to the rate of all cause mortality in late life. A one-unit decrease in idea density in early life (ie , one fewer idea expressed per 10 words in a sentence) was associated with a 49 % increase in the mortality rate (95 % CI = 17-89; p-value = 0.001). This finding did not appear to be due to confounding by birth year, education attained at the time when the autobiography was written, or age during the mortality suveillance period. Standard life table analyses indicated that the median age at death for 75-year-olds was 81.7 years for those with low idea density in early life and 88.5 years for those with high idea density in early life. Low linguistic ability in early life may reflect suboptimal cognitive and neurological development that may increase susceptibility to aging-related declines and disease processes, resulting in a higher mortality rate late in life. Overall, low linguistic ability and its correlates in early life may place potent limits on the longevity of individuals.