Case–control study of blink rate in Parkinson’s disease under different conditions

Abstract

Standard neurology texts list a reduced blink rate as one of the clinical features of Parkinson's disease. However, there are few clinical studies which have quantified this clinical sign. Here we present the results of a quantified study in a cohort of cases and controls using a standard protocol. Cases meeting standard criteria for a diagnosis of Parkinson's disease were studied together with age- and sex-matched controls. Baseline data included age, sex, duration of disease, Hoehn and Yahr stage, mini-mental state examination and treatment. Subjects were videoed undertaking three different tasks: being interviewed, watching a video, and reading from a book. Blink rates were calculated as a mean 'per minute' figure for each of the three tasks. A meta-analysis of previous studies of blink rate was undertaken. A total of 20 cases and 41 controls were studied. A decline in blink rate with increasing age was seen for cases but not controls. A significant reduction in blink rate was seen in cases when compared with controls for each of the test conditions. Blink rates were highest in subjects when being interviewed and were lowest whilst reading a passage in both cases and controls. No effect of disease duration, severity or treatment was observed. We have quantified the reduction in blink rate which has long been recognised as a feature of Parkinson's disease. We have identified factors which determine blink rate within individuals. We have also been able to define normal and abnormal levels for blink rate which may be of value clinically and for future research.

Evaluation of corneal parameters in patients with Parkinson’s disease

“…Fitzpatrick assessed the BR in patients with PD during different tasks such as watching a video, being interviewed, and reading from a book and found that BR was significantly reduced in the patients with PD compared to the healthy controls for each of the test conditions but there was no effect of disease duration, severity or treatment on BR [20]. As previously described [8,[18][19][20], in our study, we found that the patients with PD had significantly reduced BR than healthy controls and there was a significantly negative association between the BR and disease severity.…”

“…Studies reported that patients with PD had reduced blink rates compared to normal subjects, with longer pauses in voluntary blinking, small amplitude and peak velocity in spontaneous blinking [8,18,19]. A decreased BR is thought to be one of the clinical features of PD [20]. It has been suggested that this may be related to hypokinesia from decreased dopamine levels in the central nervous system [21].…”

Spontaneous Eye Blink Rate (EBR) Is Uncorrelated with Dopamine D2 Receptor Availability and Unmodulated by Dopamine Agonism in Healthy Adults

“…Additional support for the association between EBR and dopamine come from observations of aberrant EBR in individuals with neurologic or psychiatric disorders linked to dopaminergic dysfunction (e.g., Parkinson’s disease and schizophrenia), or a history of using drugs known to affect the dopamine system (e.g., cocaine; Chen et al, 1996 ; Colzato et al, 2008 ; Kowal et al, 2011 ; Fitzpatrick et al, 2012 ). This evidence is complicated by the fact that aberrant EBR is also present in nondopamine specific conditions such as intellectual disability and traumatic brain injury ( Goldberg et al, 1987 ; Daugherty et al, 1993 ; Konrad et al, 2003 ), suggesting that EBR is influenced by and reflective of multiple brain processes (see Jongkees and Colzato, 2016 for a more thorough review of evidence relating EBR to dopamine).…”

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“…Reduced and increased dopamine activity is directly associated with low and high EBR, respectively (Groman, James, Seu, Tran, Clark, Harpster, et al, 2014;Karson, 1983;1992). The decrease in blink rate in Parkinson' Disease, a condition characterized by progressive severe loss of dopaminergic neurons in the striatum (Dauer and Przedborski, 2003), is considered a classical example of EBR and dopamine association (Fitzpatrick, Hohl, Silburn, O'Gorman, & Broadley, 2012). While there is variability in the way EBR is measured, one of the most frequently used methods is direct observation and counting by a researcher (Jongkees & Colzato, 2016).…”