“…The body of evidence on the effects of HA use on cognitive decline is growing, with many cross-sectional and longitudinal studies suggesting that HA use is associated with better cognitive performance ( Deal et al, 2015 ; Castiglione et al, 2016 ; Karawani et al, 2018 ; Sarant et al, 2020 ). However, conflicting outcomes are reported, both in terms of which cognitive functions improve (e.g., significant improvement has been reported for executive function in two studies; Castiglione et al, 2016 ; Sarant et al, 2020 ) but not in a third ( Phillips et al, 2022 ) and in terms of overall outcomes, with several studies finding no association between HA use and improved cognitive performance ( Valentijn et al, 2005 ; van Hooren et al, 2005 ; Lin et al, 2013 ). As mentioned earlier, recent systematic reviews ( Sanders et al, 2021 ; Yang et al, 2022 ; Yeo et al, 2022 ) have disagreed on the effect of HA use on cognition, and the World Health Organization (WHO) currently rates the quality of the current evidence as ‘very low’, with current WHO guidelines for risk reduction of cognitive decline and dementia stating ‘there is insufficient evidence to recommend the use of HAs to reduce the risk of cognitive decline and/or dementia’ ( WHO, 2019 ).…”