Heritability of Parkinson disease in Swedish twins: a longitudinal study.
Level 3 - non-randomized controlled study
Prospective/longitudinal population-based twin cohort study.
PubMed 21482443 · doi:10.1016/j.neurobiolaging.2011.02.017
What was done
Researchers evaluated the heritability of Parkinson's disease (PD) and parkinsonism using the Swedish Twin Registry. They compared a longitudinal design (n = 46,436) against a cross-sectional design (n = 49,814), identifying cases via clinical assessments, hospital discharge records, and cause-of-death diagnoses.
What was found
In longitudinal analyses (542 twins with PD, 65 with parkinsonism): - PD concordance was 11% for monozygotic (MZ) vs 4% for same-sex dizygotic (DZ) twin pairs, yielding a heritability estimate of 34%. - Combined PD/parkinsonism concordance was 13% for MZ vs 5% for same-sex DZ twin pairs, yielding a heritability estimate of 40%. In cross-sectional analyses (287 twins with PD, 79 with parkinsonism): - PD concordance was 4% for both MZ and same-sex DZ pairs and 0 for opposite-sex pairs, resulting in a non-significant heritability estimate.
Why it matters
Earlier cross-sectional twin studies concluded PD had no significant heritability. This study shows that accounting for late onset through longitudinal tracking reveals that PD and parkinsonism are modestly heritable.
Limits
Case ascertainment partly depended on hospital discharge and death registry codes, which may miss early-stage or milder cases. The abstract does not report confidence intervals, age at onset distributions, or specific genetic or environmental risk factors, and findings reflect a single Swedish population.
Cited by
- supports Twin studies show that Parkinson's disease is only about 20% to 30% heritable/genetic.