\ua9 2023, Almindelige Danske Laegeforening. All rights reserved.INTRODUCTION. Parkinson’s disease (PD) is a widespread neurodegenerative disorder characterised by wide range of symptoms. Freezing of gait (FoG), a transient feeling that the patient’s feet are nailed to the floor, resulting in an inability to move, is a particularly distressful symptom. The assessment of FoG can be challenging. Often, clinicians are reliant on patients’ subjective experiences and patient questionnaires such as the Freezing of Gait Questionnaire (FOGQ) and its updated version, the New FOGQ (NFOGQ).Until now, the NFOGQ has not been validated and piloted for use in Danish. Therefore, few attempts have been made to assess the prevalence and severity of FoG in Danish patients with PD. METHODS. This report describes a two-step process of adapting the NFOGQ into Danish and piloting its use among a cohort of patients with PD. A satisfactory translation (Danish NFOGQ) was produced and successfully piloted. RESULTS. The translation showed robust test-retest reliability after two weeks. Patients fully understood the questionnaire. Using the Danish NFOGQ in an online prevalence survey, we found that 35.7% of respondents had experienced FoG and that the prevalence correlated with disease duration. CONCLUSION. The Danish NFOGQ appears to be appropriate for assessing FoG in Danish patients with PD in both clinical and research settings

Andersen ASM

Danielsen EH

Hvingelby VS

Johnsen E

Moller M

Pavese N

Terkelsen MH

Valdemarsen RN

English

Newcastle University E-Prints

Original ArticleDan Med J 2023;70(12):A03230209Prevalence and severity of freezing of gait ina Danish cohort of people with ParkinsonʼsdiseaseVictor Schwartz Hvingelby1*, Miriam Højholt Terkelsen1*, Rikke Nan Valdemarsen1, Anne Sofie Møller Andersen2, Erik H.Danielsen3, Mette Møller3, Nicola Pavese1, 4 & Erik Johnsen31) Department of Clinical Medicine – Nuclear Medicine and PET, Aarhus University, 2) Department of Neurosurgery, AarhusUniversity Hospital, 3) Department of Neurology, Aarhus University Hospital, Denmark, 4) Clinical Ageing Research Unit, NewcastleUniversity, Newcastle upon Tyne, UKDan Med J 2023;70(12):A03230209ABSTRACTINTRODUCTION. Parkinson’s disease (PD) is a widespread neurodegenerative disorder characterised by wide range ofsymptoms. Freezing of gait (FoG), a transient feeling that the patient’s feet are nailed to the floor, resulting in an inability tomove, is a particularly distressful symptom. The assessment of FoG can be challenging. Often, clinicians are reliant on patients’subjective experiences and patient questionnaires such as the Freezing of Gait Questionnaire (FOGQ) and its updated version,the New FOGQ (NFOGQ).Until now, the NFOGQ has not been validated and piloted for use in Danish. Therefore, few attemptshave been made to assess the prevalence and severity of FoG in Danish patients with PD.METHODS. This report describes a two-step process of adapting the NFOGQ into Danish and piloting its use among a cohort ofpatients with PD. A satisfactory translation (Danish NFOGQ) was produced and successfully piloted.RESULTS. The translation showed robust test-retest reliability after two weeks. Patients fully understood the questionnaire.Using the Danish NFOGQ in an online prevalence survey, we found that 35.7% of respondents had experienced FoG and thatthe prevalence correlated with disease duration.CONCLUSION. The Danish NFOGQ appears to be appropriate for assessing FoG in Danish patients with PD in both clinical andresearch settings.FUNDING. None.TRIAL REGISTRATION. Not relevant..Parkinsonʼs disease (PD) is a widespread neurodegenerative disorder with a point prevalence in Europe rangingfrom 0.37-0.781% at age 60 years to 1.9-4.5% at age 80 years [1]. In Denmark, the Danish Parkinsonʼs Associationestimates the prevalence to fall in the 0.7-0.8% range above age 60 years. Many patients develop symptoms ofgait impairment and postural instability. Among these, freezing of gait (FoG), a transient feeling of the patientʼsfeet being nailed to the floor, resulting in inability to move forward, is particularly distressful. Typically, FoGoccurs when negotiating crowded areas or during multi-tasking. FoG decreases patientsʼ overall mobility andincreases the risk of falls, negatively impacting quality of life and ability to function in daily living. In general,FoG represents a major milestone in the symptomatic clinical progression of the disease [2].DANISH MEDICAL JOURNAL1/8Widely implemented clinical rating scales such as the Movement Disorder Society's Unified Parkinsonʼs DiseaseRating Scale [3] have elements assessing FoG in both the clinician-rated motor component and the patientʼsActivity of Daily Living Questionnaire. However, for a more extensive assessment of the frequency, duration andseverity of FoG, other patient questionnaires such as the Freezing of Gait Questionnaire (FOGQ [4]) and theupdated New Freezing of Gait Questionnaire (NFOGQ) [5] are used.Until now, neither of these questionnaires has been translated and validated for Danish patients, despite theirusefulness in subjective experiences of FoG.The aim of this study was two-fold: Firstly, to enable Danish clinicians and researchers to gain accurate anddetailed knowledge of FoG in Danish PD patients. Secondly, to assess the prevalence and severity of FoG in aDanish cohort of PD patients. The study was conducted as a two-step process: 1) We translated and adapted theNFOGQ for use among Danish patients; and 2) we distributed the translated the NFOGQ as an online surveyaimed specifically at Danish PD patients.METHODSTranslation and cultural adaptation of the NFOGQ into DanishThe NFOGQ scale comprises nine questions. Patients are asked to evaluate the presence, duration andcomplexity of FoG over the past month. Items are rated either 0-1 or 1-4, higher scores implying more severe FoGand more impact on daily living.The NFOGQ was translated according to the guidelines of the World Health Organization (WHO) and theInternational Society of Pharmacoeconomics and Outcomes Research task force for translation and culturaladaptation [6].Forward translations and harmonisationThe team consisted of four people (MHT, RNV, ASMA and VSH). Initially, two native Danish speakers (MHT andVSH), one fluent in English, the other bilingual, independently translated the NFOGQ from English into Danish(forward translation). Both are medical doctors and are engaged in PD research. Readability was ensured inDanish without straying from the English phrasing. Forward translations were harmonised by a third nativeDanish speaker, fluent in English (RNV). Harmonisation occurred independently of the English original. Theharmonised forward translation was translated back into English (back translation) by a fourth person (ASMA).The back-translated English version was compared to the original by MHT and VSH. Changes were made to theDanish version to ensure equivalence between the Danish and English versions.The final step consisted of piloting the questionnaire on two patients with PD in person.Self-reported survey of freezing of gait in Danish patients with Parkinsonʼs diseasePatients were recruited directly through the Department of Neurology at Aarhus University Hospital, Denmark,or through advertisement through the Danish Parkinson Association. Respondents were given writteninformation about the study, names of and information about the primary investigators and informationregarding storage of responses and management of data. Written information specified that participation wasvoluntary and that consent could be withdrawn at any time by contacting an investigator. Advertisingemphasised that anyone with a diagnosis of PD could reply.The finalised translation of the questionnaire was entered as an online survey using RedCap (ResearchElectronic Data Capture) web-based software platform hosted by Aarhus University, Denmark.DANISH MEDICAL JOURNAL2/8The survey was structured into three sections. The first section contained information on the study design andrationale. The second section contained the final Danish version of the NFOGQ. A link to a video of a PD patientexperiencing an episode of FoG was embedded in this section. Participants were asked to complete thequestionnaire twice: at study entry and after two weeks to evaluate the test-retest reliability of the survey. Thefinal section of the online survey was designed to assess the validity of the translation (Validation Questionnaire).For each of the questions contained in the NFOGQ, participants had to indicate 1) whether they understood thequestion 2) whether the available responses were appropriate and 3) they were invited to give a narrativedescription of the objective of the question.The survey commenced on 1 August 2022 and terminated on 1 January 2023.Trial registration: not relevant.RESULTSIssues encountered during the translation processInitial forward translations were not entirely in agreement with each other. There was disagreement in thetranslation of “freezing of gait” as one translator opted to transfer the word “freezing” directly into thetranslation, whereas the other opted for the literal Danish translation. This discrepancy was resolved duringharmonisation into a translation of “freezing of gait”: “fastfrysning af gang”. Questions 1 and 2 did not differbetween the two forward translators. Question 3 differed in translation, as the term “turning” does not have acorrelate in Danish in the context of gait. This was solved in one of the translations by translating “turning” intotwo words and using them both, joined by a “/”. The two chosen translations specifically indicate “whenchanging direction” (“Ved retningsskift”) and “when you are trying to turn” (“når du prøver at dreje”). The nextdifference between the forward translations was observed in Question 5, as “gait initiation” does not have acorrelate in Danish. In the harmonisation, a workable translation (“når du skal tage det første skridt”) waschosen. For Question 9, the translations differed according to the word “score”. This was harmonised into theDanish word for the verb “score” (“vurdér”).Regarding back-translation, the team agreed that it was comparable to the original English in substance.The two patients who reviewed the harmonised Danish translation found that the questionnaire was easy toanswer and had no concerns or suggestions to improve it. No further changes were made to the harmonisedDanish version.Results of self-reported surveyOverall, 101 responses to the survey were received in the course of the study period. Among the 101 respondents,92 indicated a diagnosis of PD and were included in further analyses. The demographics are shown in Table 1.Among the respondents, 36 people (35.7%) indicated experiencing freezing within the past month.DANISH MEDICAL JOURNAL3/8.Results of Danish New Freezing of Gait QuestionnaireAmong the 92 respondents indicating a diagnosis of PD, 36 indicated experiencing FoG in the previous monthand 56 did not. Stratifying the prevalence of freezing by age disclosed no discernible relationship, see Figure 1 A.DANISH MEDICAL JOURNAL4/8.Correlation between prevalence and disease duration, however, was more pronounced. Indeed, whenperforming a weighted linear regression on prevalence of FoG as a function of disease duration, we achieved agood linear fit (R2 = 0.5682, p = 0.0308). The correlation indicated a 3.9 percentage point increase in prevalenceper year of living with PD with a 50% prevalence at 7.87 years.Among the 36 respondents indicating FoG, average severity according to the NFOGQ was 21.6 (95% confidenceinterval (CI): 19.3-23.9). The indicated severity, NFOGQ total score, showed no significant correlations with ageor disease duration. Severity broken down by question is indicated in Figure 2.DANISH MEDICAL JOURNAL5/8Results of the validation questionnaireIn total, 33 patients (36.23%) completed the validation questionnaire. Participants indicated that they understoodthe objective of the questions. Two participants reported problems understanding one of the Danish NFOGQquestions. One participant reported that they did not understand Question 1, indicating presence of FoG duringthe preceding month. The reason given was they had never experienced FoG.Another participant stated not understanding Question 2, concerning frequency of FoG. The reason given wasthat they did not understand why they needed to state their weekly FoG frequency when the overallquestionnaire inquiries about the previous month.Regarding suitability of response options, responses were deemed appropriate by most respondents (81.8-100%,depending on question). One person replied that they found the available responses unsuitable to their case asthey had never experienced FoG. Another person found that the available responses did not accurately reflectthe severity of their FoG and, finally, one participant responded that the available responses lackeddiscrimination between ON and OFF freezing.The respondents were prompted to describe each of the questions in the questionnaire. Respondents gaveaccurate descriptions (79.2-100%), indicating suitable phrasing of the questions. However, some of thedescriptions provided were ambiguous, making it unclear whether the participant had fully understood them.One participant offered the following description for Questions 3-6 “The question is impossible to misinterpret”(Danish: “Spørgsmålet er for mig entydigt), and another provided a similar description for Questions 4-8 (“Det ersimple spørgsmål. De kan ikke misforstås”).One respondent misinterpreted the intention of Questions 4 and 9 by describing it as referring to the state oftheir PD in general, not specifically to FoG. One participant interpreted Question 3 as being about their gaitfunction in general, not specifically about FoG. Finally, one respondent offered a “?” as explanation for Question7.Retest resultsIn total, 19 respondents completed the retest. The range of discrepancy in the test-retest was 13 (–7-6) points.However, there were outliers as the mean change was 2.16 points (95% CI: 1.11-3.20 points) and the median 2points.DANISH MEDICAL JOURNAL6/8DISCUSSIONHere, we have detailed the process of translating and adapting the NFOGQ into Danish for use among Danish-speaking PD patients. We assessed the applicability of the Danish NFOGQ and the prevalence of FoG in thiscohort.The adaptation of the NFOGQ into Danish produced an easy to read and understand questionnaire that may beused in the clinic to evaluate the presence, duration, complexity and severity of FoG. However, an importantpoint, which was also raised by one of the respondents, is the questionnaireʼs lack of discrimination between ONand OFF states. Given this, we have amended the Danish version. The Danish version now contains an additionalitem (Question 6.a): “Hvor stor en procentdel af dine fastfrysninger finder sted imens din parkinson medicinvirker, som den skal? Det vil sige, når du har taget din medicin som du skal, og du føler den virker.” (Eng: Whatpercentage of your episodes of freezing occur while your medication for Parkinsonʼs disease is working asintended? That is, when you have ingested your medication as prescribed and feel as though it is workin.”) Theavailable answers to the question are 0%, less than 25%, 26-50%, 51-75% or 76-100% (Danish: 0% Jeg har ingenfastfrysninger, imens min medicin virker, mindre end 25%, mere end 25 men mindre en 50%, 51-75%, 75-100%,alle eller næsten alle mine fastfrysninger er imens, jeg har taget min medicin, og den virker). The final DanishNFOGQ, including this adjustment, is provided in Appendix 1.The prevalence of FoG in our survey was 35.7%. Furthermore, we were able to confirm a significant correlationbetween disease duration and the prevalence of FoG.However, other estimates of FoG prevalence vary between studies with ranges from 5% to 85.9% [4, 7, 8]. A largesystematic review of 66 studies calculated a weighted mean prevalence of 50.6%. Our results seem to agree withthis finding.As in the original English questionnaire, the version of the Danish NFOGQ used for the online survey containedno specific question to differentiate between FoG occurring in the ON or OFF state. Therefore, we are unable toreport whether the 35.7% of the patients who reported FoG in our study were experiencing ON-FoG, OFF-FoG orboth. This distinction may have significant clinical implications. In fact, if the episodes of freezing occurredduring the OFF states, this would suggest that a significant proportion of respondents were not optimallymedicated. One reason for this may be that the patients themselves do not recognize FoG as a symptom ofdopamine deficiency, poor compliance or related factors. Hopefully, the adjusted version of the Danish NFOGQprovided in Appendix 1 will allow clinicians and researchers to obtain this information. It will also allowresearchers to better identify patients with episodes of FoG exclusively during the ON medication state. This willbe crucial for future studies designed to achieve a better understanding of the pathophysiology of ON-FoG andnovel treatments [9].CONCLUSIONOur validation indicated that the questionnaire is readily understood by patients and is robust across time.Furthermore, our cohort-based survey indicated that FoG is a prominent symptom among Danish patients withPD....DANISH MEDICAL JOURNAL7/8Correspondence Victor Schwartz Hvingelby. E-mail: au340287@clin.au.dk *) Shared first authorshipAccepted 28 September 2023Conflicts of interest Potential conflicts of interest have been declared. Disclosure forms provided by the authors are available withthe article at ugeskriftet.dk/dmjAcknowledgements The authors extend their gratitude to professors A. Nieuwboer and N. Giladi for granting free use of theNFOGQ for translation into Danish. We wish to acknowledge the patients who participated in the survey and the Danish ParkinsonAssociation (Da: Parkinsonforeningen) for their help in distributing the questionnaire among potential respondents. Finally, aspecial thank you to the pilot patients for helping the team refine the translation.Cite this as Dan Med J 2023;70(12):A03230209Open Access under Creative Commons License CC BY-NC-ND 4.0Supplementary  https://content.ugeskriftet.dk/sites/default/files/2023-09/a03230209-supplementary.pdfREFERENCES1. Pringsheim T, Jette N, Frolkis A, Steeves TDL. The prevalence of Parkinson's disease: a systematic review and meta-analysis.Mov Disord. 2014;29(13):1583-90.2. Bloem BR, Hausdorff JM, Visser JE, Giladi N. Falls and freezing of gait in Parkinson's disease: a review of two interconnected,episodic phenomena. Mov Disord. 2004;19(8):871-84.3. Goetz CG, Tilley BC, Shaftman SR et al. Movement Disorder Society-sponsored revision of the Unified Parkinson's DiseaseRating Scale (MDS-UPDRS): scale presentation and clinimetric testing results. Mov Disord. 2008;23(15):2129-70.4. Giladi N, Shabtai H, Simon ES et al. Construction of freezing of gait questionnaire for patients with Parkinsonism.Parkinsonism Relat Disord. 2000;6(3):165-70.5. Nieuwboer A, Rochester L, Herman T et al. Reliability of the new freezing of gait questionnaire: agreement between patientswith Parkinson's disease and their carers. Gait Posture. 2009;30(4):459-63.6. Wild D, Grove A, Martin M et al. Principles of good practice for the translation and cultural adaptation process for patient-reported outcomes (PRO) measures: report of the ISPOR Task Force for Translation and Cultural Adaptation. Value Health.2005;8(2):94-104.7. Lilleeng B, Gjerstad M, Baardsen R et al. Motor symptoms after deep brain stimulation of the subthalamic nucleus. ActaNeurol Scand. 2015;131(5):298-304.8. Zhang WS, Gao C, Tan YY, Chen SD. Prevalence of freezing of gait in Parkinson's disease: a systematic review and meta-analysis. J Neurol. 2021;268(11):4138-50.9. Hvingelby VS, Glud AN, Sørensen JCH et al. Interventions to improve gait in Parkinson's disease: a systematic review ofrandomized controlled trials and network meta-analysis. J Neurol. 2022;269(8):4068-79.DANISH MEDICAL JOURNAL8/8

Prevalence and severity of freezing of gait in a Danish cohort of people with Parkinsonʼs disease

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Prevalence and severity of freezing of gait in a Danish cohort of people with Parkinsonʼs disease

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