Loneliness Independently Increases Risk for Parkinson Disease After 5 Years

Among people who report feelings of loneliness, the risk of developing Parkinson disease (PD) is higher, independent of known genetic, clinical, behavioral, and social risk factors, according to study findings published in JAMA Neurology.

Researchers at Florida State University in the United States and the Université de Montpellier in France conducted a large, prospective, population-based, cohort study using UK Biobank data on loneliness collected at 22 assessment centers across the United Kingdom from March 13, 2006 to October 1, 2010. Loneliness was assessed using a survey in which 491,603 participants who were not currently diagnosed with PD answered “yes” or “no” to the question, “Do you often feel lonely?”

Next, the researchers examined subsequent UK National Health Service (NHS) records for diagnosis codes indicating incident PD up until October 9, 2021. During the follow-up period which lasted 15.58 years, 2822 out of these 491,603 individuals developed incident PD, resulting in an incidence rate of 47 per 100,000 person-years.

Of these 2822 participants who developed PD, 2273 (80.5%) previously denied loneliness, while the remaining 549 (19.5%) had reported loneliness. The researchers confirmed that individuals who reported loneliness demonstrated a higher risk for developing incident PD (hazard ratio [HR], 1.37; 95% CI, 1.25-1.51).

This association between loneliness and PD incidence persisted even after accounting for confounding variables, including smoking status, body mass index (BMI), physical activity levels, polygenetic risk score for PD, and a medical history of diabetes, stroke, hypertension, myocardial infarction, depression, and documented visits to a psychiatrist (adjusted HR, 1.25; 95% CI, 1.12-1.39). Additionally, age (HR for interaction, 0.99), biological sex (HR for interaction, 0.98), and genetics (HR for interaction, 0.93) did not significantly influence the relationship between loneliness and PD incidence.

When analyzing the temporal component of PD incidence, the researchers observed that loneliness was not associated with risk for PD during the first 5 years after assessment of loneliness (HR, 1.15; 95% CI, 0.91-1.45); however, during the next 10 years of the study’s follow-up period, loneliness was associated with PD risk (HR, 1.32; 95% CI, 1.19-1.46).

“This study adds evidence on the detrimental health impact of loneliness and supports recent calls for the protective and healing effects of personally meaningful social connection,” the researchers concluded.

Study limitations included the observational study design precluding determination of causality or reverse causality and inability to generalize results to populations living in countries other than the UK. Additionally, underestimation of the association between loneliness and PD may have occurred due to the potential that PD diagnosis was missed during early stages of development, or hospital admission or death records did not adequately capture this information as many participants with PD may not have been hospitalized during the follow-up period. The use of a single-item assessment of loneliness compared with multi-item scales, which may have led to increased error variance, also resulting in underestimation of the association between loneliness and PD.