The influence of education in predicting conversion from Subjective cognitive decline (SCD) to objective cognitive impairment: A systematic review and meta-analysis

Background: Subjective cognitive decline (SCD) is considered a pre-symptomatic stage of dementia characterized by cognitive complaints. The ability of education to reduce the risk of dementia is well known. Our objective is to investigate the influence of education on the risk of progression from SCD to MCI or dementia. Methods: Prospective longitudinal studies of adults (>= 50 years) with SCD evaluating progression to objective cognitive decline, MCI, or dementia were selected. Pooled estimates (random effects model) and 95 % confidence intervals were calculated, exploring heterogeneity. Standardized education differences, Odds Ratio, or Hazard Ratio between converters and non-converters were estimated. Results: The systematic review carried out showed that high education, as well as other cognitive reserve proxies, delays cognitive decline. The first meta-analysis showed a significant association of SCD with conversion in both high and low education strata. A second meta-analysis considering education as a continuous variable found that SCD converters showed two years less education than non-converters. Conclusions: Our results suggest that education has a delaying effect against cognitive decline progression. The presumed improvement in accurately detecting cognitive decline associated with better metacognitive skills in higher-educated SCD participants does not seem to neutralize the incremental risk of objective cognitive decline associated with lower educational attainment.