Social isolation, characterized by a lack of social interaction and smaller social networks, is a growing concern, especially among older adults. Loneliness, a subjective emotional state of dissatisfaction with social relationships, is a related concept. Extensive research has linked both social isolation and loneliness to negative health outcomes, including increased mortality, poorer immune function, disrupted sleep, and increased susceptibility to stress. These detrimental effects have been compared to the health risks of smoking or obesity. The increasing prevalence of Parkinson's Disease (PD), coupled with the inherent challenges of social engagement faced by individuals with PD and their caregivers (stigma, communication difficulties, etc.), creates a significant risk for social isolation within this population. This study aimed to directly examine the relationship between social isolation and PD symptom severity and quality of life, particularly in light of the COVID-19 pandemic and its associated social distancing measures.

The existing literature demonstrates a strong correlation between social isolation and various negative health outcomes. Studies have shown links between loneliness and stress-related physiological responses, cognitive impairment, sleep disturbances, and weakened immune function. In aging populations, social isolation has been shown to be as detrimental to health as smoking or obesity. A significant body of research emphasizes the protective role of social support in buffering stress and promoting overall well-being. However, research on social isolation specifically within the context of Parkinson's Disease is limited. While the “Parkinson Pandemic” itself is a growing concern due to increased prevalence, the compounding effect of social isolation necessitates further investigation.

This cross-sectional analysis used baseline data from a larger prospective observational internet-based study (IRB #1433-132, NCT01214191) designed to identify modifiable lifestyle variables associated with the rate of patient-reported PD symptoms. The study included 1795 participants with a self-reported diagnosis of idiopathic PD. The primary outcome measure for PD severity was the cumulative Patient-Reported Outcomes in PD (PRO-PD) score. The PRO-PD assesses the severity of 33 common PD symptoms. Quality of life (QoL) was assessed using the PROMIS Global measure. Social health was evaluated through questions related to loneliness, friendships, partnership status, social performance, and social satisfaction. Statistical analyses were conducted to assess the associations between social health measures and PRO-PD scores and QoL, adjusting for age, gender, income, and years since diagnosis.

The study found a strong association between social isolation and worsened PD severity and lower quality of life. Individuals who reported feeling lonely had significantly higher PRO-PD scores (55% greater symptom severity) compared to those who did not feel lonely (p < 0.01). Participants with a lot of friends had 21% fewer symptoms than those with few or no friends (p < 0.01). The PRO-PD scores positively correlated with loneliness and negatively correlated with measures of social function and satisfaction. Loneliness predicted QoL better than tremor severity. Furthermore, the response to the statement "I am lonely" was as negatively impactful on PRO-PD scores as daily exercise was positive. Modifiable lifestyle variables, such as stress, stress management techniques, and exercise, were also associated with PD progression. The study also found that being in a relationship was positively associated with improved quality of life, while marital status appeared to correlate with quality of life.

The study's findings underscore the significant impact of social isolation on PD symptom severity and quality of life. While the cross-sectional design prevents causal inferences, the results strongly suggest that addressing social isolation may be crucial for improving outcomes in PD. The observed association between loneliness and increased symptom severity across all 33 PRO-PD symptoms warrants further investigation into potential underlying mechanisms, such as the role of stress and its interplay with PD symptoms. The implications of these findings are particularly relevant in the context of the COVID-19 pandemic, where social distancing measures have further exacerbated social isolation. This study highlights the urgent need for proactive interventions, including virtual support groups and social prescribing programs, to mitigate the negative effects of social isolation on individuals with PD.

This study demonstrates a strong association between social isolation and worsened Parkinson's disease severity and quality of life. The results emphasize the critical need to address social isolation as a modifiable risk factor in PD management, particularly in light of the ongoing COVID-19 pandemic. Future research should explore causal relationships and the efficacy of interventions designed to improve social health and mitigate the impact of social isolation on PD progression and QoL.

The study's cross-sectional design limits the ability to establish causality. The reliance on self-reported data may be subject to recall bias and the influence of other PD symptoms, such as depression or fatigue. The predominantly Caucasian, young, and female sample may limit the generalizability of the findings to the broader PD population. Additionally, the relatively new PRO-PD scale lacks extensive historical use, though it showed correlation with other established measures.