Validity and reliability of the Chinese (Singapore) version of the Parkinson’s Disease Questionnaire (PDQ-39)

Objective: The purpose of the study was to validate the Chinese (Singapore) version of the Parkinson’s Disease Questionnaire (PDQ-39CSV) and its briefer version (PDQ-8CSV). Methods: A convenience sample of Chinese-speaking Singaporeans with Parkinson’s disease (PD) (n=63) completed a questionnaire containing the PDQ-39CSV and the Chinese (Singapore) EQ-5D. A subgroup also participated in a retest and/or a focus group discussion. A priori hypotheses were tested by examining correlations between PDQ-39CSV, PDQ-8CSV and EQ-5D scores and using principal component factor analysis. Reliability was assessed using Cronbach’s α and intra-class correlation coefficients (ICC). Results: Thirty-two PDQ-39CSV items correlated satisfactorily with their hypothesized dimensions (Spearman’s ρ ≥ 0.4). Factor analysis yielded a component on which all 8 PDQ-39CSV dimensions were substantially loaded (loading range: 0.53–0.89). As hypothesized, the PDQ-39CSV and PDQ-8CSV summary indices were highly correlated (Pearson’s r:0.95, ICC:0.94); correlations between related PDQ and EQ-5D scores were generally strong (Spearman’s ρ: 0.38–0.76, p<0.001 for all). Cronbach’s α values ranged from 0.64 to 0.90 and ICC values from 0.66 to 0.86. Conclusion: This study provides preliminary evidence supporting validity and reliability of both the PDQ-39CSV and its briefer version.     

Responsiveness of the EQ-5D and 8-item Parkinson’s Disease Questionnaire (PDQ-8) in a 4-year follow-up study

Objective  

The purpose of this study was to evaluate the responsiveness of the EQ-5D and the Parkinson’s Disease Questionnaire (PDQ-8) to deterioration in health-related quality of life (HRQoL) in patients with Parkinson’s disease (PD).     

Quality of life in Parkinson’s disease patients: validation of the Short-Form Eight-item Parkinson’s Disease Questionnaire (PDQ-8) in Taiwan

Purpose  

This study sought to evaluate the Chinese version of the eight-item Parkinson’s Disease Questionnaire (PDQ-8), through standard psychometric techniques.     

Commentary on the paper “Reliability and validity of the Swedish version of the Fatigue Impact Scale (FIS)”

Abstract

Limited awareness of disabilities is common in mild cognitive impairment and dementia. In order to get a broader base in planning interventions, it is important to consider a person's awareness of his/her disability encountered in performance. The aim of this study was to examine the relationship between occupational performance and awareness of disability in older adults with mild cognitive impairment or dementia. Thirty-five older adults were evaluated with the AMPS (Assessment of Motor and Process Skills) and with the AAD (Assessment of Awareness of Disability). Many-faceted Rasch models generated individual measures of ADL performance and awareness of disability. Non-parametric correlation statistics were used to analyse the relationships. The findings showed that there was an overall positive relationship between occupational performance and awareness of disability. However, individual variations in the sample implied that limitations in performance were not equivalent to a limited awareness of disability. In conclusion, awareness of disability should be individually evaluated when planning interventions together with clients and their families.     

Mapping of the PDQ-39 to EQ-5D scores in patients with Parkinson’s disease

Purpose

The EuroQoL (EQ-5D) is ideal to compare quality of life across conditions. However, the Parkinson’s Disease Questionnaire (PDQ-39) is often the only quality-of-life instrument used in Parkinson’s disease research. We aimed to identify associations between PDQ-39 domains and EQ-5D domains, and compare different methods of developing a function to map the PDQ-39 to EQ-5D scores.

Methods

Adults with Parkinson’s disease self-completed both instruments. Ordinal regression identified associations between PDQ-39 domain scores and each EQ-5D domain. Modeling (n = 80) and validation sets (n = 16) were randomly generated. Overall performance of four methods of mapping the PDQ-39 to EQ-5D scores (using PDQ-39 domains and total score in ordinal and linear regression) was assessed with the validation set, followed by assessing the equivalence of observed and predicted EQ-5D scores on the full dataset controlling for sociodemographic factors.

Results

Different sets of PDQ-39 domains were associated with each EQ-5D domain. For example, PDQ-39 “Activities of Daily Living” and “Social Support” were associated with EQ-5D “Personal Care,” while PDQ-39 “Emotional Well-being” was associated with EQ-5D “Anxiety/Depression.” Over one-third (37.5 %) of predictions from ordinal regressions had an error <0.01 % (compared to 6.3 % for linear regressions). The EQ-5D scores predicted with ordinal regression using PDQ-39 domains were similar in distribution and association with sociodemographic factors to the observed EQ-5D scores.

Conclusions

Of the four methods tested, using PDQ-39 domains in ordinal regression was superior for mapping EQ-5D scores. The function reported here may prove particularly useful for cost-utility analyses comparing Parkinson’s disease with other conditions.     

Multiple Antioxidants in the Prevention and Treatment of Parkinson’s Disease

Parkinson’s disease (PD) is one of the major progressive neurological disorders for which no preventative or long-term effective treatment strategies are available. Epidemiologic studies have failed to identify specific environmental, dietary or lifestyle risk factors for PD except for toxic exposure to manganese, meperidine (Demerol®, the “designer drug” version of which often contains a toxic byproduct of the synthesis, 1-methyl-4-phenyl 1,2,3,6 tetrahydropyridine [MPTP]), and some herbicides and pesticides. The search for genetic risk factors such as mutation, overexpression or underexpression of nuclear genes in DA neurons in idiopathic PD has not been successful as yet. Polymorphism in certain genes appears to be a risk factor, but there is no direct evidence for the causal relationship between polymorphism and increased risk of PD. In familial PD, mutation in the α-synuclein gene is associated with the disease, but a direct role of this gene in degeneration of DA neurons remains to be established. Although mutations in the Parkin gene has been associated with autosomal recessive juvenile Parkinson’s disease, the role of this gene mutation in causing degeneration of DA neurons has not been defined. We have reported that in hereditary PD, a mutation in the α-synuclein gene may increase the sensitivity of DA neurons to neurotoxins. We hypothesize that, in idiopathic PD, epigenetic (mitochondria, membranes, protein modifications) rather than genetic events are primary targets which, when impaired, initiate degeneration in DA neurons, eventually leading to cell death. Although the nature of neurotoxins that cause degeneration in DA neurons in PD is not well understood, oxidative stress is one of the intermediary risk factors that could initiate and/or promote degeneration of DA neurons. Therefore, supplementation with antioxidants may prevent or reduce the rate of progression of this disease. Supplementation with multiple antioxidants at appropriate doses is essential because various types of free radicals are produced, antioxidants vary in their ability to quench different free radicals and cellular environments vary with respect to their lipid and aqueous phases. L-dihydroxyphenylalanine (L-dopa) is one of the agents used in the treatment of PD. Since L-dopa is known to produce free radicals during its normal metabolism, the combination of L-dopa with high levels of multiple antioxidants may improve the efficacy of L-dopa therapy.     

Systematic Review of the Prevalence and Incidence of Parkinson’s Disease in Asia

Background

Parkinson’s disease (PD) is a common neurodegenerative disorder in older people, and half of the world’s older population lives in Asia. However, the epidemiology of PD in Asian countries is poorly understood. This review assembles evidence on the prevalence and incidence of PD in Asian countries and identifies gaps in our present knowledge.

Methods

A systematic search of studies published from 1965 to October 2008 was conducted using MEDLINE and EMBASE. The selection criteria were defined a priori. Prevalence and incidence were standardized to the WHO World Standard Population 2000. Twenty-one original studies were selected for the review. Two studies that described the ethnic origin of participants and contained Asian populations were also included in the analysis.

Results

Excluding one study with questionably low prevalence and incidence, the remaining studies reported a standardized all-age prevalence of 51.3 to 176.9 per 100 000 in door-to-door surveys; prevalence in record-based studies ranged from 35.8 to 68.3 per 100 000. The standardized incidence rates were 8.7 per 100 000 person-years in door-to-door surveys and 6.7 to 8.3 per 100 000 person-years in record-based surveys.

Conclusions

The prevalence of PD in Asian countries was slightly lower than that in Western countries. However, comparison of incidence was difficult because of the small number of studies. Varying methodologies, diagnostic criteria, and case-finding strategies contributed to the considerable variation in the reported prevalence and incidence of PD.Key words: epidemiology, prevalence, incidence, Parkinson’s disease, Asia     

Validation of the Japanese translation of the Swallowing Disturbance Questionnaire in Parkinson’s disease patients

Purpose

The Swallowing Disturbance Questionnaire (SDQ) was developed as a self-rated screening tool for dysphagia in patients with Parkinson??s disease (PD). We developed the Japanese version of this questionnaire (SDQ-J), according to the cross-cultural adaptation guidelines, and examined its reliability.

Methods

Subjects were 61 Japanese patients with PD (mean age, 67.0?±?9.2?years) who answered the SDQ-J before undergoing videofluoroscopic examination of swallowing (VF). We compared the findings of the questionnaire with the patients?? aspiration status during VF.

Results

Cronbach??s alpha coefficient for the 15 questions of the SDQ-J was 0.84. According to the SDQ-J, 15 patients (24.6%) were diagnosed with dysphagia, while 9 patients (14.8%) aspirated liquid during VF. The sensitivity and specificity of the SDQ-J in predicting aspiration were 77.8 and 84.6%, respectively; therefore, the SDQ-J significantly predicted aspiration during VF (P?Conclusions The SDQ-J appears to be a reliable and useful screening tool for Japanese PD patients with aspiration. As the NPV was higher than the PPV in the SDQ-J, this questionnaire could potentially be used for early identification of severe dysphagia in patients with PD.     

Associations between B Vitamins and Parkinson’s Disease

B vitamins may correlate with Parkinson’s disease (PD) through regulating homocysteine level. However, there is no comprehensive assessment on the associations between PD and B vitamins. The present study was designed to perform a meta-analytic assessment of the associations between folate, vitamin B6, and vitamin B12 and PD, including the status of B vitamins in PD patients compared with controls, and associations of dietary intakes of B vitamins and risk of PD. A literature search using Medline database obtained 10 eligible studies included in the meta-analyses. Stata 12.0 statistical software was used to perform the meta-analysis. Pooled data revealed that there was no obvious difference in folate level between PD patients and healthy controls, and PD patients had lower level of vitamin B12 than controls. Available data suggested that higher dietary intake of vitamin B6 was associated with a decreased risk of PD (odds ratio (OR) = 0.65, 95% confidence intervals (CI) = (0.30, 1.01)), while no significant association was observed for dietary intake of folate and vitamin B12 and risk of PD. PD patients had lower level of vitamin B12 and similar level of folate compared with controls. Dietary intake of vitamin B6 exhibited preventive effect of developing PD based on the available data. As the number of included studies is limited, more studies are needed to confirm the findings and elucidate the underpinning underlying these associations.     

Epidemiology and etiology of Parkinson’s disease: a review of the evidence

The respective contribution of occupational and behavioural factors to social disparities in all-cause mortality has been studied very seldom. The objective of this study was to evaluate the role of occupational and behavioural factors in explaining social inequalities in premature and total mortality in the French working population. The study population consisted of a sample of 2,189 and 1,929 French working men and women, who responded to a self-administered questionnaire in mid-1996, and were followed up until the end of 2008. Mortality was derived from register-based information and linked to the baseline data. Socioeconomic status was measured using occupation. Occupational factors included biomechanical and physical exposures, temporary contract, psychological demands, and social support, and behavioural factors, smoking, alcohol abuse, and body mass index. Significant social differences were observed for premature and total mortality. Occupational factors reduced the hazard ratios of mortality for manual workers compared to managers/professionals by 72 and 41%, from 1.88 (95% CI: 1.17–3.01) to 1.25 (95% CI: 0.74–2.12) for premature mortality, and from 1.71 (95% CI: 1.18–2.47) to 1.42 (95% CI: 0.95–2.13) for total mortality. The biggest contributions were found for biomechanical and physical exposures, and job insecurity. The role of behavioural factors was very low. Occupational factors played a substantial role in explaining social disparities in mortality, especially for premature mortality and men. Improving working conditions amongst the lowest social groups may help to reduce social inequalities in mortality.     

Reliability and validity of the Iranian version of the Pediatric Quality of Life Inventory™ 4.0 Generic Core Scales in adolescents

Objective  

The objective of this study was to investigate the reliability and validity of the Iranian version of the Pediatric Quality of Life Inventory™ 4.0 (PedsQL™ 4.0) Generic Core Scales in adolescents     

Evaluating the Serbian version of the KIDSCREEN quality-of-life questionnaires: reliability, validity, and agreement between children’s and parents’ ratings

Purpose

To evaluate the psychometric properties of the Serbian set of the KIDSCREEN questionnaires: KIDSCREEN-52, KIDSCREEN-27, and KIDSCREEN-10 index.

Methods

The study included 330 children (8–18 years) and 314 parents. All completed the KIDSCREEN and KINDL questionnaires. Psychometric analyses included internal consistency reliability (Cronbach’s coefficient), criterion, convergent and discriminant validity, and agreement between children and parents (the intraclass correlation coefficient—ICC).

Results

Cronbach’s α of 0.7 and above was found for all except for the self-perception scale of the KIDSCREEN-52, being 0.58 for the child and 0.63 for the parent version. Correlations between similar scales in the KIDSCREEN and KINDL were substantial (ranging 0.45–65) and higher than correlations between theoretically different scales. Moderate to excellent agreement existed between children’s and parents’ ratings in all KIDSCREEN scales (ICC ranged 0.44–0.63), except for the moods and emotions from the longer (ICC = 0.34) and the social support and peers from the shorter version (ICC = 0.38).

Conclusions

Levels of internal consistency reliability and validity of all KIDSCREEN questionnaires in Serbian are appropriate, as well as agreement between children’s and parents’ ratings.     

A Study of the Relationship between Health and Subjective Well-Being in Parkinson’s Disease Patients

ObjectivesGovernments are turning their attention to evidence on subjective measures of well-being to inform policy decisions. In the context of health, there is, therefore, growing interest in understanding how measures of health-related quality of life relate to subjective well-being and whether subjective well-being could provide a basis for resource allocation decisions in the future. This study investigates the relationship between health-related quality of life, as measured by the EuroQol five-dimensional (EQ-5D) questionnaire, and subjective well-being in Parkinson’s disease.MethodsA paper questionnaire including the EQ-5D questionnaire, four key subjective well-being questions taken from the Integrated Household Survey in England, and other demographic details was distributed to people with Parkinson’s disease in the United Kingdom. Responses were used to estimate multiple regression models explaining subjective well-being using the EQ-5D questionnaire index (UK weights), EQ-5D questionnaire dimensions and the visual analogue scale, and patients’ sociodemographic characteristics.ResultsA total of 199 responses were received. Combining visual analogue scale and EQ-5D questionnaire dimensions, especially anxiety/depression and, to a lesser extent, mobility, yielded the best-fitting models (adjusted R² range 0.36–0.53). Patients with Parkinson’s disease living in care homes report lower levels of subjective well-being than do those living alone. These effects are not captured by the health-related quality-of-life measures in the analysis.ConclusionsUsual health-related quality-of-life measures can partially explain different well-being dimensions, yet they fail to capture part of the broader impact of disease on subjective well-being. Further empirical research into the relationship between subjective well-being and the EQ-5D Parkinson’s disease longitudinally, and in different disease areas, is required, and further standardization of subjective well-being measures is recommended.     

Association of Cumulative Lead Exposure with Parkinson’s Disease

Background

Research using reconstructed exposure histories has suggested an association between heavy metal exposures, including lead, and Parkinson’s disease (PD), but the only study that used bone lead, a biomarker of cumulative lead exposure, found a nonsignificant increase in risk of PD with increasing bone lead.

Objectives

We sought to assess the association between bone lead and PD.

Methods

Bone lead concentrations were measured using ¹⁰⁹Cd excited K-shell X-ray fluorescence from 330 PD patients (216 men, 114 women) and 308 controls (172 men, 136 women) recruited from four clinics for movement disorders and general-community cohorts. Adjusted odds ratios (ORs) for PD were calculated using logistic regression.

Results

The average age of cases and controls at bone lead measurement was 67 (SD = 10) and 69 (SD = 9) years of age, respectively. In primary analyses of cases and controls recruited from the same groups, compared with the lowest quartile of tibia lead, the OR for PD in the highest quartile was 3.21 [95% confidence interval (CI), 1.17–8.83]. Results were similar but slightly weaker in analyses restricted to cases and controls recruited from the movement disorders clinics only (fourth-quartile OR = 2.57; 95% CI, 1.11–5.93) or when we included controls recruited from sites that did not also contribute cases (fourth-quartile OR = 1.91; 95% CI, 1.01–3.60). We found no association with patella bone lead.

Conclusions

These findings, using an objective biological marker of cumulative lead exposure among typical PD patients seen in our movement disorders clinics, strengthen the evidence that cumulative exposure to lead increases the risk of PD.     

Life Events and the Onset of Celiac Disease from a Patient’s Perspective

Stressful events have been investigated in various immune-mediated diseases but not in celiac disease. Our aim was to examine the relationship of stressful events assessed by the standardized interview of Paykel with the diagnosis of celiac disease in comparison to patients, with a diagnosis of gastroesophageal reflux disease used as the control group. Adults with celiac disease (n = 186) reported more frequent and more severe life events in the years prior to the diagnosis than control patients (n = 96) (67.2% vs. 37.5%, p < 0.001, mean Paykel score 11.5 vs. 13.4, p = 0.001, respectively). Findings were not significantly different between celiac disease and control patients for the time lapse between the event and the diagnosis (mean 5.5 vs. 5.7 months). Pregnancy was defined as a negative event by 20.3% of celiac women, but never by control women. Findings were confirmed when analyses were repeated in the subgroup of patients of both groups with diagnosis made within one year of onset of symptoms. Data indicate that, before diagnosis, the number of stressful events in celiac disease was more frequent although less severe than in the control group suggesting that life events may favor the clinical appearance of celiac disease or accelerate its diagnosis.     

Dopamine Transporter Genetic Variants and Pesticides in Parkinson’s Disease

Background

Research suggests that independent and joint effects of genetic variability in the dopamine transporter (DAT) locus and pesticides may influence Parkinson’s disease (PD) risk.

Materials

Methods: In 324 incident PD patients and 334 population controls from our rural California case–control study, we genotyped rs2652510, rs2550956 (for the DAT 5′ clades), and the 3′ variable number of tandem repeats (VNTR). Using geographic information system methods, we determined residential exposure to agricultural maneb and paraquat applications. We also collected occupational pesticide use data. Employing logistic regression, we calculated odds ratios (ORs) for clade diplotypes, VNTR genotype, and number of susceptibility (A clade and 9-repeat) alleles and assessed susceptibility allele–pesticide interactions.

Results

PD risk was increased separately in DAT A clade diplotype carriers [AA vs. BB: OR = 1.66; 95% confidence interval (CI), 1.08–2.57] and 3′ VNTR 9/9 carriers (9/9 vs. 10/10: OR = 1.8; 95% CI, 0.96–3.57), and our data suggest a gene dosing effect. Importantly, high exposure to paraquat and maneb in carriers of one susceptibility allele increased PD risk 3-fold (OR = 2.99; 95% CI, 0.88–10.2), and in carriers of two or more alleles more than 4-fold (OR = 4.53; 95% CI, 1.70–12.1). We obtained similar results for occupational pesticide measures.

Discussion

Using two independent pesticide measures, we a) replicated previously reported gene–environment interactions between DAT genetic variants and occupational pesticide exposure in men and b) overcame previous limitations of nonspecific pesticide measures and potential recall bias by employing state records and computer models to estimate residential pesticide exposure.

Conclusion

Our results suggest that DAT genetic variability and pesticide exposure interact to increase PD risk.     

Vitamin D and Sunlight Exposure in Newly-Diagnosed Parkinson’s Disease

Circulating vitamin D has previously been found to be lower in patients with Parkinson’s disease (PD), while the effects of sunlight exposure have not yet been fully investigated. Therefore, we evaluated the associations between serum vitamin D, vitamin D intake, sunlight exposure, and newly-diagnosed PD patients in a Chinese population. This case-control study measured serum 25-hydroxyvitamin D (25(OH)D) levels and sunlight exposure in 201 patients with newly-diagnosed PD and 199 controls without neurodegenerative diseases. Data on vitamin D intake and sunlight exposure were obtained using a self-report questionnaire. Multivariable logistic regressions were employed to evaluate the associations between serum 25(OH)D levels, sunlight exposure, and PD. Adjustments were made for sex, age, smoking, alcohol use, education, BMI, and vitamin D intake. There were significantly lower levels of serum 25(OH)D (20.6 ± 6.5 ng/mL), daily vitamin D intake (8.3 ± 3.7 g/day), and sunlight exposure (9.7 ± 4.1 h/week) in patients with PD compared to healthy controls (p < 0.05). Crude odds ratios (ORs) for PD in the quartiles of serum 25(OH)D were 1 (reference), 0.710 (0.401, 1.257), 0.631 (0.348, 1.209), and 0.483 (0.267, 0.874), respectively. Crude ORs for PD in quartiles of sunlight exposure were 1 (reference), 0.809 (0.454, 1.443), 0.623 (0.345, 1.124) and 0.533 (0.294, 0.966), respectively. A significant positive correlation between serum 25(OH)D and sunlight exposure was found, but serum 25(OH)D was not correlated with daily vitamin D intake. This study indicates that lower levels of serum 25(OH)D and sunlight exposure are significantly associated with an increased risk for PD.