An Additional Year of Early Life Education Correlates with a Small Reduction in Late Life Dementia Risk
Education, intelligence, socioeconomic status, and healthy longevity are all correlated with one another in human populations. No concrete determination of the mechanisms that make this the case has yet been established, but there is no shortage of hypothesizing on the topic. Does education produce an effect through the greater socioeconomic status that it tends to produce, or is there, for example, some physical benefit arising from a greater use of the brain during developmental years that lasts for long enough to affect neurodegeneration in late life? Or it is that more intelligent people tend to be more educated, and thus intelligence is the factor that one needs to look at for causation? And so forth. Here, researches present results that argue more for a contribution of physical effects in the brain than for other possibilities.
Lower educational attainment has been identified as a major risk factor for Alzheimer's disease and related dementias (ADRD). However, little is known about whether and how much of this association reflects a causal effect from education to ADRD. Part of the challenge in distinguishing correlation from causation is that third factors, such as childhood circumstances, socioeconomic background, and genetics, may confound the relationship between education and ADRD. Also, there may be individual characteristics, such as self-control, that drive both behavioral risk factors and educational attainment.
We overcome these challenges by combining a natural experiment with dementia data constructed from administrative health records for a large cohort. In 1972, England, Scotland, and Wales increased the minimum age at which students could drop out of school from 15 to 16 years of age. The reform affected only students born after September 1, 1957, generating a discontinuity in the relationship between education and date of birth. We exploit this discontinuity to estimate the causal effect of education on dementia incidence.
We found that this additional schooling induced by a natural experiment in the United Kingdom in the early 1970s subsequently reduced the cumulative incidence of ADRD in affected cohorts by approximately 0.88%. These results suggest that ADRD incidence can be modified by social policy, a welcome finding given the expected exponential growth in cases of dementia and their large costs. Encouragingly, we also found that the school reform mitigated the genetic risk of developing ADRD - rejecting the common perception that the influence of genetics on diseases such as ADRD cannot be altered by environmental interventions.