title: Low muscle strength in late adolescence and Parkinson disease later in life.
abstract: OBJECTIVE
  To evaluate maximal isometric muscle force at 18 years of age in relation to Parkinson disease (PD) later in life.
  
  
  METHODS
  The cohort consisted of 1,317,713 men who had their muscle strength measured during conscription (1969-1996). Associations between participants' muscle strength at conscription and PD diagnoses, also in their parents, were examined using multivariate statistical models.
  
  
  RESULTS
  After adjustment for confounders, the lowest compared to the highest fifth of handgrip strength (hazard ratio [HR] 1.38, 95% confidence interval [CI] 1.06-1.79), elbow flexion strength (HR 1.34, 95% CI 1.02-1.76), but not knee extension strength (HR 1.24, 95% CI 0.94-1.62) was associated with an increased risk of PD during follow-up. Furthermore, men whose parents were diagnosed with PD had reduced handgrip (fathers: mean difference [MD] -5.7 N [95% CI -7.3 to -4.0]; mothers: MD -5.0 N [95% CI -7.0 to -2.9]) and elbow flexion (fathers: MD -4.3 N [95% CI -5.7 to -2.9]; mothers: MD -3.9 N [95% CI -5.7 to -2.2]) strength, but not knee extension strength (fathers: MD -1.1 N [95% CI -2.9 to 0.8]; mothers: MD -0.7 N [95% CI -3.1 to 1.6]), than those with no such familial history.
  
  
  CONCLUSIONS
  Maximal upper extremity voluntary muscle force was reduced in late adolescence in men diagnosed with PD 30 years later. The findings suggest the presence of subclinical motor deficits 3 decades before the clinical onset of PD.
authors.affiliation: From Geriatrics (H.G., P.N.) and Rehabilitation Medicine (S.S.), Department of Community Medicine and Rehabilitation, Clinical Neuroscience (J.A.), Department of Pharmacology and Clinical Neuroscience, and Occupational and Environmental Medicine (A.N.), Department of Public Health and Clinical Medicine, Umeå University, Sweden.
authors.forename: Helena
authors.initials: H
authors.lastname: Gustafsson
authors.affiliation: From Geriatrics (H.G., P.N.) and Rehabilitation Medicine (S.S.), Department of Community Medicine and Rehabilitation, Clinical Neuroscience (J.A.), Department of Pharmacology and Clinical Neuroscience, and Occupational and Environmental Medicine (A.N.), Department of Public Health and Clinical Medicine, Umeå University, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Aasly
authors.affiliation: From Geriatrics (H.G., P.N.) and Rehabilitation Medicine (S.S.), Department of Community Medicine and Rehabilitation, Clinical Neuroscience (J.A.), Department of Pharmacology and Clinical Neuroscience, and Occupational and Environmental Medicine (A.N.), Department of Public Health and Clinical Medicine, Umeå University, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Stråhle
authors.affiliation: From Geriatrics (H.G., P.N.) and Rehabilitation Medicine (S.S.), Department of Community Medicine and Rehabilitation, Clinical Neuroscience (J.A.), Department of Pharmacology and Clinical Neuroscience, and Occupational and Environmental Medicine (A.N.), Department of Public Health and Clinical Medicine, Umeå University, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Nordström
authors.affiliation: From Geriatrics (H.G., P.N.) and Rehabilitation Medicine (S.S.), Department of Community Medicine and Rehabilitation, Clinical Neuroscience (J.A.), Department of Pharmacology and Clinical Neuroscience, and Occupational and Environmental Medicine (A.N.), Department of Public Health and Clinical Medicine, Umeå University, Sweden. peter.nordstrom@germed.umu.se.
authors.forename: Peter
authors.initials: P
authors.lastname: Nordström
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D010290:Parents; D010300:Parkinson Disease / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D016016:Proportional Hazards Models; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
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