Background
This systematic review provides a comprehensive synthesis of recent epidemiological evidence that environmental noise negatively impacts human cognition.

Methods
We update a prior review with recent publications (PROSPERO CRD42019151923). The strength of evidence for associations was assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluations) framework. We also conducted random-effects meta-analyses where suitable.

Results
16 studies were identified and reviewed in tandem with 32 studies previously reviewed by Clark & Paunovic (2018). A meta-analysis from 3 studies found that reading comprehension scores in quiet classrooms were 0.80 (95% confidence interval: 0.40; 1.20) points higher than children in noisier classrooms. Meta-analysis of the impact of 1 dB (dB) increase in environmental noise on reading and language abilities gave a pooled beta coefficient of −0.11(95% confidence interval: −0.32; 0.10). A meta-analysis of Odds Ratios (OR) from 3 studies found higher odds of cognitive impairment in people aged 45 + with higher residential noise exposure (OR 1.40, 95% CI: 1.18;1.61). After qualitative synthesis of remaining studies, there was high quality evidence for an association between environmental noise and cognitive impairment in middle-to-older adults, moderate quality evidence for an association between aircraft noise and reading and language in children, and moderate quality evidence against an association between aircraft noise and executive functioning in children. Generally the literature was supportive for other cognitive outcomes, but with low or very low-quality evidence.

Discussion
The evidence so far suggests that noise exposure is associated with cognition, but more good quality research using standardised methodology is required to corroborate these results and to allow for precise risk estimation by larger meta-analyses. There is also a need for more research with older teenagers and young-to-middle aged adults, on the synergistic effects of noise and air pollution, and in Africa, Central and South America, South Asia and Australasia.