title: Physical and cognitive fitness in young adulthood and risk of amyotrophic lateral sclerosis at an early age.
abstract: There is a clinical impression that patients with amyotrophic lateral sclerosis (ALS) have a higher level of physical fitness and lower body mass index (BMI) than average. However, there is a lack of literature examining the relationship between cognitive fitness and ALS risk. In this study we explored the associations of both physical and cognitive fitness with future risk of ALS.
  
  
  
  Data on physical fitness, BMI, intelligence quotient (IQ) and stress resilience were collected from 1 838 376 Swedish men aged 17-20 years at conscription during 1968-2010. Their subsequent ALS diagnoses were identified through the Swedish Patient Register. Hazard ratios (HRs) and 95% CIs from flexible parametric models were used to assess age-specific associations of physical fitness, BMI, IQ and stress resilience with ALS.
  
  
  
  We identified 439 incident ALS cases during follow-up (mean age at diagnosis: 48 years). Individuals with physical fitness above the highest tertile tended to have a higher risk of ALS before the age of 45 years (range of HRs: 1.42-1.75; statistically significant associations at age 41-43 years) compared with others. Individuals with BMI ≥ 25 tended to have a lower risk of ALS at all ages (range of HRs: 0.42-0.80; statistically significant associations at age 42-48 years) compared with those with BMI < 25. Individuals with IQ above the highest tertile had a statistically significantly increased risk of ALS at an age of 56 years and above (range of HRs: 1.33-1.81), whereas individuals with stress resilience above the highest tertile had a lower risk of ALS at an age of 55 years and below (range of HRs: 0.47-0.73).
  
  
  
  Physical fitness, BMI, IQ and stress resilience in young adulthood might be associated with the development of ALS at an early age.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.
authors.forename: E
authors.initials: E
authors.lastname: Longinetti
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.
authors.forename: D
authors.initials: D
authors.lastname: Mariosa
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.|Department of Medical Sciences, Örebro University, Örebro.
authors.forename: H
authors.initials: H
authors.lastname: Larsson
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.|Lung and Allergy Unit, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Almqvist
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.
authors.forename: P
authors.initials: P
authors.lastname: Lichtenstein
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.
authors.forename: W
authors.initials: W
authors.lastname: Ye
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm.
authors.forename: F
authors.initials: F
authors.lastname: Fang
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D015992:Body Mass Index; D003071:Cognition / Q000502:physiology*; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010808:Physical Examination; D010809:Physical Fitness / Q000502:physiology*; D055500:Resilience, Psychological; D012306:Risk; D013548:Sweden; D055815:Young Adult
keywords: amyotrophic lateral sclerosis; body mass index; cohort study; intelligence quotient; physical fitness; stress resilience