Blink rates in patients with schizophrenia compared to healthy controls: A meta-analysis
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Background
Eyeblink rates vary with cognitive states and may be related to dopaminergic activity. Early reports have found elevated blink rates in patients with schizophrenia, possibly related to hyperdopaminergia, but findings appear inconsistent. We performed a systematic review and meta-analysis to evaluate the evidence regarding blink rates in patients with schizophrenia compared to healthy controls and the impact of medication.
Methods
We registered a protocol for the review on PROSPERO. We searched PubMed, SCOPUS, and Embase, performed title- and abstract-screening, full-text screening, data extraction, and risk-of-bias assessment. We calculated meta-level effect sizes, assessed effect size heterogeneity, and tested for small-study effects.
Results
We included 22 studies in the systematic review and of those, 19 in the meta-analysis. The studies included a total of 632 patients and 791 healthy controls. The risk of bias was high in all but two studies, particularly due to the lack of blinding and confounding by medication. Meta-analysis revealed an elevated blink rate in patients with schizophrenia (irrespective of medication status) compared to healthy controls (Hedges’ g = 0.48; 95% CI [0.13,0.82]). Stratified meta-analyses revealed elevated blink rates in unmedicated patients with schizophrenia compared with healthy controls (Hedges’ g = 0.83; 95% CI [0.34, 1.31]), but not in medicated patients compared with controls (Hedges’ g = -0.09; 95% CI [-0.64, 0.46]).
Conclusion
Blink rates are elevated in unmedicated, but not medicated, patients with schizophrenia compared with healthy controls. These findings motivate further study of the link between blink rates, central dopamine, and schizophrenia.
