Improved nutritional status is related to improved quality of life in Parkinson’s disease

Quality of life is positively associated with quality of health [1] and is therefore recognised as an important outcome for the treatment of many conditions, including Parkinson’s disease (PD). Reports about quality of life in PD indicate that it is poor compared to that of the general population [2],[3] and in other conditions, [4],[5] with virtually all aspects of the disease contributing to poorer quality of life. These include longer disease duration, [6] older age at disease onset, [7] more severe motor symptoms, [4],[6],[8],[9] decreases in mobility [10] and the ability to carry out activities of daily living, [9],[11],[12] increases in the amount of medication required, [4],[12] medication ineffectiveness, [4],[13],[14] dyskinesias, [13],[15],[16] pain, [8],[10] problems with sleep, [4],[8],[10] cognitive impairment, [17] depression, [8]-[12],[14] and anxiety [10],[12],[14].

Poor nutritional status, specifically malnutrition, results in a lower quality of life in the elderly [18],[19] and other disease states [20]-[22]. People with PD are at risk of malnutrition; [23]-[25] therefore, it is possible that malnutrition in PD contributes to poorer quality of life, as a recent study demonstrated, with significant correlations between nutritional status and quality of life [26]. Factors affecting a person’s food intake, such as difficulties swallowing and loss of appetite, play an important role in quality of life [27]. Nutrition interventions aimed at improving these symptoms and, therefore, nutritional status can improve quality of life, as has previously been demonstrated in chronic kidney disease [22] and oncology [21],[28],[29] patients. Despite the extensive research related to quality of life in PD, there is limited evidence regarding the relationship between malnutrition and quality of life. There is also a paucity of information available about the results of nutrition interventions for malnutrition in PD in general and also as they affect quality of life.

The aim of the current study was to determine the relationship between nutritional status and quality of life in people with PD.

The research was carried out in two phases. Informed written consent for both phases was obtained as per protocol approved by the Queensland University of Technology Human Research Ethics Committee.

In Phase I, community-dwelling people with idiopathic PD, aged >18 years, were recruited using a variety of methods between February and August 2011 [25]. Participants were excluded if they resided in an assisted living facility. Geographical location was limited to within ~2-hour driving distance of Brisbane, Queensland, Australia. PD diagnosis was determined by the participants’ physician or neurologist and was self-reported by the participant. Only a portion of the total data collected, as it relates to nutritional status and quality of life, is presented here, with other information regarding clinical status, motor symptoms, and non-motor symptoms reported previously [25],[30].

For the majority of the participants, the assessments were conducted in their home, and the visit was scheduled to be within an hour of a PD medication dose or at a time when the participants stated that their function was best, to try to capture their function in an “On” state. The scored Patient-Generated Subjective Global Assessment (PG-SGA) was performed by a dietitian to assess nutritional status [31]. Nutrition assessment using the PG-SGA is based on a medical history (recent changes in weight, dietary intake, gastrointestinal symptoms, functional capacity, and disease status) and a physical examination of fat stores, muscle status, and fluid status. The assessment results in a categorisation of nutrition status: SGA-A (well nourished), SGA-B (moderately malnourished), or SGA-C (severely malnourished) [32], as well as a total score with a higher score indicating poorer nutritional status. The PG-SGA score places people into triage categories indicating the need for nutrition or medical intervention: 0-1 points (category 1, no intervention required), 2-3 points (category 2, patient and family education required), 4-8 points (category 3, requires intervention by dietitian), ≥9 (category 4, critical need for symptom management and/or nutrition intervention).

The Parkinson’s Disease Questionnaire (PDQ-39) [33] was completed to assess quality of life related to PD. A higher score indicates poorer quality of life. It was completed by the participants while the researcher was present in order that instructions could be provided that an answer of “Always” or “Cannot do at all” was appropriate if they no longer performed a task due to the difficulties associated with their PD. In the case of poor cognitive status, as assessed by the Addenbrooke Cognitive Examination, the spouse or caregiver was asked to assist with completing the questionnaire. Each of the PDQ-39 sub-scores was also calculated: mobility, activities of daily living (ADL), emotional well-being (EWB), stigma, social support, cognition, communication, and bodily discomfort. The Unified Parkinson’s Disease Rating Scale (UPDRS) motor sub-scale (III) was completed as previously described [30]. Birth date and self-reported disease duration (PD duration) were collected.

During Phase II, participants were considered eligible when they were assessed as being at risk of malnutrition or malnourished in Phase I using one of the following criteria: SGA category B or C, Mini-Nutritional Assessment (MNA) score ≤23.5, PG-SGA score ≥9, BMI <22 kg/m² for participants aged ≥65 years, or BMI <18 kg/m² for participants aged ≤64 years. The inclusion criteria included both those at risk of malnutrition and malnourished in order to follow the recommendation that those at risk of malnutrition should receive some intervention [34] and to provide a sample size of 20 participants, given the time limitations of the study. Exclusion criteria included current management by a dietitian, hospitalisation at the time of intervention, deep brain stimulation scheduled within the next 3 months, significant recent improvement in nutritional status prior to Phase I, intentional weight loss resulting in reduced intake and low MNA score, and MNA score ≤23.5 or BMI < age-specific cut-offs but no significant changes in diet history, anthropometry, recent weight history, or functional status and were deemed to be of normal nutritional status by the dietitian [35].

The participants were randomised to 2 groups (SC: standard care; INT: intervention) using a random number generator to assign participant numbers, and the group assignments were placed in sealed envelopes, with the number on the outside, by a research associate not associated with the project. Rolling recruitment was conducted to allow for Phase II to run concurrently with the end of Phase I. As eligible participants agreed to participate, they were assigned the next consecutive number, which identified the envelope to open to determine the group assignment.

The aim of Phase II was to improve nutritional status over a 12-week period. The SC group received written information only while the INT group received individualised nutrition information by a dietitian and weekly phone contact. The participants were informed of the groups, including that one would include more information and contact than the other. Each participant was involved in 4 visits: 1. Instruction visit (pre-BL) one week prior to the baseline time point; 2. Baseline measurements (BL); 3. 6-week measurements (6 wk); 4. 12-week measurements (12 wk). These visits were conducted at the same time every visit, similar to the Phase I timing for as close to an “On” state as possible, and the assessments were performed in the same order to minimise the effects of medication on the outcomes. Written consent was obtained at the pre-BL visit. The PDQ-39, SGA, and PG-SGA were completed at the BL, 6 wk, and 12 wk visits but not the pre-BL visit. The Hoehn and Yahr (H&Y) scale, which is a five-point scale (1-5) with a higher rating on the scale indicating a greater amount of disability and impairment, was recorded. The H&Y scores were dichotomized (less severe PD, H&Y 0-3; severe PD, H&Y 4-5). Current medications were collected at each of the 4 visits, and the levodopa equivalent doses (LEDD) were calculated per kg body weight (mg/kg). Changes in medication were at the treating physician’s or neurologist’s discretion and were not controlled in the study. All participants who required further intervention received referrals to a dietitian after completion of the project.

The current paper aimed to explore the relationship between nutritional status and quality of life and also to investigate the effect of a nutrition intervention on quality of life in PD. In the current study, those who were malnourished reported lower quality of life across the majority of PDQ-39 domains, and there were significant relationships between nutritional status (PG-SGA scores) and PDQ-39 scores, indicating poorer quality of life in those with poorer nutritional status and supporting previous findings in a sample of PD patients attending a movement disorders clinic in Iran [26].

The strongest relationships existed between nutritional status and the areas of mobility and activities of daily living, and these were the domains that differentiated the well-nourished and malnourished. Similar results were recently reported in the study based in Iran, with the strongest correlation between the PDQ-39 mobility sub-score and nutritional status [26]. Therefore, perceived limitations in mobility may have the greatest relationship with nutritional status in PD. However, the precedence of these relationships cannot be determined owing to the cross-sectional nature of the present study. Poor mobility and the inability to carry out ADL can contribute to poor nutritional status [37]. On the other hand, malnutrition reduces mobility [38] and functional status, [18],[39] and the ability to carry out activities of daily living plays an important part in quality of life [27],[40]. Similarly, the finding of poorer social support in those with poorer nutritional status may be due to the fact that people with PD who live alone are more likely to be malnourished [30]. Social support plays an important role in maintaining nutritional status, particularly in a disease that results in considerable disability [37] and nutrition impact symptoms that can decrease food intake [25]. Therefore, these relationships should be explored further to determine the influence of the variables on each other.

There was also a positive relationship between changes in PG-SGA and PDQ-39 scores during the 12-week intervention period, regardless of the group (SC or INT) (Table 4). Although these results only bordered on significance, potentially because of the small sample size, the findings might indicate that improvements in nutritional status result in improvement in quality of life in PD.

Quality of life scores improved in both groups over the 12-week period, although these changes were not statistically significant. However, the INT group demonstrated a trend towards greater improvement than the SC group in the majority of domains, which resulted in clinically significant changes. The collaborative and personalised advice and the regular phone contact with a health professional in the INT group may have improved the group’s overall sense of well-being. It has been shown that patient involvement in medical treatment decisions increases the satisfaction with that treatment in people with PD, and this may also extend to nutrition-related interventions [41]. Participation in the study also resulted in significantly improved emotional well-being for the entire group. Perhaps even semi-regular contact with a health professional may improve the sense of being looked after.

There was also a large degree of variability in the responses as is demonstrated by the wide ranges within each PDQ-39 score. Within the INT group, there were three individuals who experienced changes in their health, unrelated to PD, in the weeks prior to the final data collection, resulting in poorer quality of life scores for them at that final time point. In addition, there were participants in both groups with missing data, particularly for the PDQ-39, because they did not want to finish the visit. This may have affected the comparison between the groups at those times. Furthermore, the quality of life in this sample was better than that reported in other studies, [14],[42] which could limit the ability to affect a significant change in quality of life. The short study period of only 12 weeks may not have allowed for meaningful changes in quality of life to occur.

The choice of tool with which to measure quality of life may have also affected the results. It has been argued that the PDQ-39 measures health status (HS) rather than quality of life, where HS refers to function levels, and quality of life reflects internal experiences or the subjective evaluation of health [43]. The PDQ-39 is weighted toward physical symptoms and therefore may not appropriately measure health-related quality of life [44]. This may explain why the only significant improvement was found in the emotional well-being domain over the intervention period. Additionally, other important health related areas may be missing from the PDQ-39, such as those relating to motor fluctuations and medications [45] which may be influenced by body weight and nutritional status [46]-[48]. Finally, the use of self-reported PD diagnosis to identify participants may influence the generalisability of the results to patients with idiopathic PD, as not all patients are aware of their specific diagnosis (e.g., idjiopathic, drug-induced, progressive supranuclear palsy, multiple system atrophy).

Malnourished people with PD presented with poorer quality of life than well-nourished participants. This was particularly evident in the areas of mobility and activities of daily living, both of which have been associated with poor nutritional status in other groups. Given the borderline significant relationship between improvements in nutritional status during the nutrition intervention and improvements in quality of life, it is likely that future studies conducted in larger samples would support this finding. Furthermore, the nutrition intervention resulted in improvements in emotional well-being. Attention to nutritional status is an important component of quality of life and therefore the total care of people with PD.