Tremor or Stiffness? Alternative Screening Definitions for Population-Based Identification of Parkinsonian Symptoms in Kenya and Senegal

​Introduction Population-based studies use different screening definitions to identify parkinsonian symptoms. Whether these definitions identify the same individuals and produce comparable prevalence estimates is unknown. We compared four bradykinesia-based screening definitions in population-based studies from Kenya and Senegal. Methods We analysed cross-sectional data from 3,574 adults aged 60 years and older participating in population-based studies in Kenya and Senegal. Bradykinesia was defined using the Parkinsonism Screening Questionnaire as the concurrent presence of difficulty buttoning or dressing and reduced arm swing. Four screening definitions requiring bradykinesia together with tremor, stiffness, both symptoms, or either symptom were compared. Symptom co-occurrence, agreement between definitions, and prevalence estimates were evaluated. Results Among 3,574 participants (mean age 68.7 years [SD 7.7]; 1,859 [52.0%] women), 115 (3.2%; 95% CI 2.7-3.9) met the predefined definition of bradykinesia. Among these participants, 66 (57.4%) reported both tremor and stiffness, 45 (39.1%) reported stiffness without tremor, four (3.5%) reported neither symptom, and none reported tremor without stiffness. Definitions requiring tremor identified 66 participants (1.86%; 95% CI 1.47-2.36), compared with 111 (3.13%; 95% CI 2.60-3.75) identified by definitions requiring stiffness. Similar patterns were observed across countries, age groups, and sex. Conclusion Alternative screening definitions were not interchangeable in population-based identification of parkinsonian symptoms. Definitions requiring tremor and stiffness identified different screen-positive populations and produced different prevalence estimates. Consistent specification of screening definitions will improve comparisons across epidemiological studies and support planning for neurological services.