Parkinson’s disease (PD) is the second most common progressive neurodegenerative disease and is characterized by motor and non-motor symptoms. Constipation is a frequent non-motor symptom and may result from a combination of slow colonic transit and defecatory dysfunction. Furthermore, pharmacological treatment for PD, including levodopa, may exacerbate constipation as an adverse effect.

Reported prevalence of constipation in PD varies widely (16 - 72%), likely reflecting heterogeneity in definitions and assessment methods.[1] The Rome IV criteria provide a standardized framework for diagnosing functional constipation, capturing multiple (clinically relevant) symptom domains and improving comparability across studies.

While prevalence has been described, little is known about patient-reported severity of constipation symptoms in PD. Assessing symptom severity is essential to better understand the clinical burden of constipation and may help differentiate underlying mechanisms, and guide more targeted treatment strategies. Therefore, this cross-sectional study aimed to provide a comprehensive assessment of constipation in PD by evaluating both prevalence and patient-reported symptom severity.

An online survey was conducted in the Netherlands among people (≥18 years) with a self-reported diagnosis of PD who were able to complete a questionnaire. Demographics were collected. Constipation was defined using the ROME IV criteria, categorizing participants into constipated (PD-C) and non-constipated (PD-NC) groups.
Symptom severity was assessed using the Patient Assessment of Constipation Symptoms questionnaire (PAC-SYM), a validated 12-item instrument covering three domains: abdominal, rectal, and stool symptoms. Items are scored on a 5-point Likert scale (0-4), with higher scores indicating greater severity. Only fully completed questionnaires were included. Descriptive statistics were used to summarize baseline characteristics. PAC-SYM total and domain scores were calculated as mean item scores, as well as medians and interquartile ranges (IQR, Q1-Q3). 
Based on an expected constipation prevalence of 50% in the estimated population of 36.000 PD patients in the Netherlands, a sample size of 315 participants was required to achieve a two-sided 95% confidence interval with a width of 0.11.

A total of 452 participants were included (median age 70 years), of whom 67.5% met criteria for constipation. The mean total PAC-SYM score was 0.83 (IQR 0.48-1.25) for the full cohort. There was a significantly higher score in the PD-C than the PD-NC group (mean 1.08 vs. 0.33, p <0.001).(Table 1) No sex differences in total scores were observed.

The stool domain showed the highest symptom severity overall. Straining was the most frequently reported symptom (97.4%) and the most severe, with 46.9% of constipated participants reporting it as severe or very severe.(Figure 1)

Constipation affects nearly 70% of people with PD, consistent with previous studies. This study is one of the first to quantify patient-reported symptom severity in this population. Stool-related symptoms, particularly straining, represent the greatest burden. 
The predominance of straining and stool-related symptoms suggests that outlet-type dysfunction may contribute substantially to PD-related constipation. This may indicate pelvic floor dyssynergia, characterized by impaired coordination of pelvic floor and abdominal muscles during defecation.[2] In such cases, dietary or pharmacological treatments may be insufficient. Pelvic floor muscle training with biofeedback has proven effective in treating constipation in the general population but has not been adequately studied in PD. Therefore, targeted pelvic floor muscle training with biofeedback should be explored as a potential treatment option.

Constipation is highly prevalent in PD and is associated with substantial symptom burden, particularly stool-related symptoms such as straining. These findings highlight the need for targeted treatment approaches and further research into the potential role of pelvic floor muscle training and biofeedback therapy in PD.

Knudsen K, Krogh K, Østergaard K, Borghammer P. Constipation in parkinson's disease: Subjective symptoms, objective markers, and new perspectives. Mov Disord. 2017;32(1):94–105.
Rao SS. Dyssynergic defecation and biofeedback therapy. Gastroenterol Clin North Am. 2008;37(3):569–86, viii.