Umami and Other Taste Perceptions in Patients With Parkinson's Disease

Insights into salt perception and cognitive impairment among middle-aged and older adults: a scoping review

BACKGROUND

A decline in taste sensitivity from aging leads people with a higher salt threshold to frequently add more salt to their food, which attributed to decreased cognitive efficiency. This scoping review aimed to gather the latest evidence on the relationship between salt perception and cognitive impairment which is essential in the development of new intervention and prevention strategies.

METHODS

Studies published between January 2014 and March 2024 were searched across four databases: PubMed, the Cochrane Library, Scopus, and EBSCO. Data extraction involved gathering details on the study design, participant demographics, methods for assessing cognitive function and salt perception, considering confounding factors, and synthesizing the primary outcomes.

RESULTS

Six studies were included in the analysis, five cross-sectional studies and a longitudinal study. These studies revealed various associations between salt perception and cognitive impairment. Specifically, findings from a three-year longitudinal study suggested that lower salt sensitivity was associated with poorer cognitive scores, which is consistent with the results of two other studies. However, the remaining three studies did not find significant differences (p > 0.05) in salt taste perception related to cognitive status. Furthermore, a study identified executive function as another significant factor influencing salt taste perception.

CONCLUSION

These findings highlight the link between cognitive decline in salt perception, which provide an indication of salt intake and related health risks. There is a need to explore the mechanisms of salt taste sensitivity and its impact on cognitive health should be encouraged.

Chemosensory Impairments and Their Impact on Nutrition in Parkinson's Disease: A Narrative Literature Review

Parkinson's disease (PD) is a neurological disorder characterized by heterogeneous symptomatology, in which the classical motor features of Parkinsonism are associated with clinically significant non-motor symptoms. Olfactory alteration, as a manifestation of PD's premotor or prodromal phase, is well known. These impairments can lead to malnutrition, decreased appetite, and depression, thereby worsening patients' quality of life. However, only a few studies clarify the mechanisms, characteristics, and clinical diagnostic and therapeutic implications of impaired taste perception. Moreover, unlike most motor features of PD, non-motor symptoms often have limited treatment options or responses. The purpose of this review is to collate and describe all relevant studies on taste and smell alterations in patients with PD and how these alterations could affect nutritional status. Our search aimed to identify English-language research articles and reviews published in peer-reviewed journals over the past two decades (2004-2024), while also including older foundational studies when relevant. Several studies show that hyposmia in PD worsens over time, potentially linked to structural changes in the brain's basal ganglia and piriform cortex. Severe hyposmia is also associated with a higher risk of dementia in PD patients and can negatively influence quality of life, affecting social interactions and nutrition. Regarding taste perception, recent studies have suggested that hypogeusia may occur even in the prodromal stage of PD, such as in patients with REM sleep disorder, although the exact mechanisms remain unclear. Additionally, research has explored the role of bitter taste receptors and their possible involvement in inflammation and α-synuclein misfolding, suggesting a link between taste dysfunction and immune system changes in PD. Attention was then focused on the gut microbiota's link to the central nervous system and its contribution to gustatory dysfunctions, as well as how the nasal microbiome influences PD progression by altering the olfactory system. Nowadays, the primary role of a correct diet in the overall treatment of PD patients is becoming increasingly important for practitioners. Diet should be included among the available aids to counteract some aspects of the pathology itself. For all these reasons, it is also crucial to determine whether these chemosensory impairments could serve as disease markers, helping to better understand the underlying mechanisms of the disease.

How do people with Parkinson's disease perceive challenges in handling cutlery? - A mixed study

Aim: Investigate the experiences, challenges, and difficulties faced by people with Parkinson's disease (PD) when using standard cutlery during meals and explore their preferences for features in assistive cutlery.

Methods: This study employed a mixed-methods, narrative, and descriptive approach using phenomenological methodology. Data were collected in two phases: Phase 1 focused on understanding participants' experiences and difficulties through phone or video interviews, while Phase 2 involved home visits to evaluate their preferences for cutlery features. Structured interviews with open- and closed-ended questions were transcribed and analyzed thematically. Analyst triangulation was employed to ensure reliability.

Results: Phase one included 41 participants, while phase two included 15. Most participants reported difficulties using standard cutlery, citing challenges such as spills and reduced grip stability. Despite these difficulties, few had prior experience with assistive devices. Barriers to using adaptive cutlery included lack of awareness, limited access, cost, and concerns about its appearance. Some participants reported feeling embarrassed, which led them to avoid dining with others. Suggestions for improving regular cutlery focused on increasing the depth of forks and spoons to minimize spills. Most participants expressed a preference for cutlery with textured handles, deeper bowls, and medium size and weight.

Conclusion: People with PD experience difficulties using regular cutlery, and few are aware of or use assistive devices. Participants expressed a desire for improvements in cutlery design that could improve their dining experience. Textured handles, medium size and weight, and deeper bowls were the most popular preferences among participants.These design improvements have the potential to enhance the dining experience and promote greater social participation among individuals with PD.

Apnea behavior in early- and late-stage mouse models of Parkinson's disease: Cineradiographic analysis of spontaneous breathing, acute stress, and swallowing

This study aimed to evaluate the timing and frequency of spontaneous apneas during breathing and swallowing by using cineradiography on mouse models of early/initial or late/advanced Parkinson's disease (PD). C57BL/6 J mice received either 6-OHDA or vehicle injections into their right striatum, followed by respiratory movement recordings during spontaneous breathing and swallowing, and a stress challenge, two weeks later. Experimental group animals showed a significantly lower respiratory rate (158.66 ± 32.88 breaths/minute in late PD, 173.16 ± 25.19 in early PD versus 185.27 ± 25.36 in controls; p<0.001) and a significantly higher frequency of apneas (median 1 apnea/minute in both groups versus 0 in controls; p<0.001). Other changes included reduced food intake and the absence of swallow apneas in experimental mice. 6-OHDA-induced nigrostriatal degeneration in mice disrupted respiratory control, swallowing, stress responsiveness, and feeding behaviors, potentially hindering airway protection and elevating the risk of aspiration.

The missing piece of the puzzle - The key role of the dietitian in the management of Parkinson's disease

The current paradigm for the multidisciplinary management of Parkinson's Disease (PD) does not include regular nutritional assessment despite research showing that 90 % of people living with Parkinson's (PwP) lack access to basic dietetic services. Since many non-motor symptoms such as dysphagia, constipation and orthostatic hypotension and PD complications such as weight loss and sarcopenia can be improved through dietary intervention, dietitians are a critical missing piece of the PD management puzzle. This paper serves to review the role of dietitians and medical nutrition therapy in management of PD as well as a call to action for future studies to investigate improvement of nutritional status and quality of life for all PwP.

Body mass index in patients with Parkinson's disease: a systematic review

Body mass index (BMI) has been found to have an impact on neurodegenerative diseases such as Parkinson's disease (PD). Several studies suggested that patients with PD have a lower BMI compared with controls. However, some studies indicated the differences between patients and controls as statistically insignificant. We performed this meta-analysis to clarify the relationship between BMI and PD based on the studies published from 1975 to April 2023 in the PubMed, Embase, and Cochrane Library databases. In total, 18 case-control studies met the inclusion criteria for meta-analysis. We found a statistically significant difference in mean BMI between patients with PD and healthy controls {standardized mean difference (SMD) [95% confidence interval (CI)] = -0.36 (-0.43, -0.29), P < 0.05}. Regarding sex, seven studies were included in the meta-analysis for female/male patients with PD. The mean BMI was significantly different between males with PD and healthy males [SMD (95% CI) = -0.34 (-0.47, -0.22), P < 0.05]. Moreover, the mean BMI of females with PD was significantly different from that of corresponding healthy females [SMD (95% CI) = -0.44 (-0.57, -0.30), P < 0.05]. The meta-analysis demonstrates a significantly lower BMI in patients with PD, but no gender differences, when compared with their respective healthy individuals.NEW & NOTEWORTHY The meta-analysis demonstrates a significantly lower body mass index in patients with PD, but no gender differences, when compared with their respective healthy individuals.

Gustatory dysfunction is related to Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Olfactory dysfunction has been reported to be involved in Parkinson's disease (PD) pathogenesis. However, gustatory dysfunction in PD has not been evaluated as in-depth as olfactory dysfunction. We reviewed the previously published studies regarding gustatory function in PD patients and suggested the possibility that gustatory dysfunction may also be associated with PD.

METHODS

MEDLINE, Cochrane Library, Embase, and PubMed databases were searched for studies evaluating gustatory function in PD patients. We used the standardized mean difference and a 95% confidence interval (CI) as the effect analysis index regarding the taste strip test. The relative risk and 95% CI were used as the effect analysis index for the questionnaires and propylthiouracil (PTU)/phenylthiocarbamide (PTC) perception test. Statistical heterogeneity was assessed using forest plots, Cochran's Q, and the I2 statistic; heterogeneity was considered high when I2 was over 75%. Publication bias was assessed by funnel plots and the Egger bias test.

RESULTS

We identified 19 articles that reported the results of gustatory function tests in PD patients and healthy controls. Most of these studies used various gustatory tests, including taste strips, questionnaires, taste solutions, PTU/PTC perception tests, and electrogustometry, and reported significantly lower gustatory function in PD patients than in the controls. However, several articles reported contradictory results.

CONCLUSIONS

Based on these studies, gustatory dysfunction is closely related to PD. However, the number of studies and enrolled subjects was small, and a unified gustatory function test was lacking. Therefore, further studies with larger populations and normalized gustatory function tests are needed.