Comorbid conditions associated with Parkinson's disease: a population-based study.

The burden of comorbidity in Parkinson's disease (PD) remains unclear. All Olmsted County, Minnesota, residents with incident PD in 1976-1995 (n = 197) plus one age- and sex-matched non-PD referent subject per case were followed for all clinical diagnoses from 5 years before through 15 years after index (i.e., year of PD onset for each case and same year for the referent subject). Both members of a case-referent pair were censored at death or emigration of either member to ensure equivalent follow-up. Cases and referent subjects were compared for summary comorbidity (Charlson index) and for the likelihood of having one or more diagnoses within each International Classification of Diseases chapter/subchapter. Before index, the groups were similar for all comparisons. After index, cases had a higher likelihood of diagnoses within the chapters "Mental Disorders" and "Diseases of the Genitourinary System," and within the subchapters "Organic Psychotic Conditions," "Other Psychoses," "Neurotic/Personality/Other Nonpsychotic Disorders," "Hereditary/Degenerative Diseases of Central Nervous System," "Symptoms," "Other Diseases of Digestive System," "Other Diseases of Urinary System," "Diseases of Veins/Lymphatics/Other Circulatory System Diseases," "Fractures of Lower Limb," "Other Diseases of Skin/Subcutaneous Tissue," "Osteopathies/Chrondropathies/Acquired Musculoskeletal Deformities," and "Pneumonia and Influenza." The excess morbidity and mortality observed for persons with PD are consistent with recognized PD sequelae.