Public defence: Ola Nakken Ola Nakken at Institute of Clinical Medicine will be defending the thesis “Epidemiology of Amyotrophic Lateral Sclerosis: A population-based study in Norway” for the degree of PhD (Philosophiae Doctor).

Image may contain: Clothing, Martial arts uniform, Chin, Neck.

Photo: Geir Boye Lindhjem.

Trial Lecture – time and place

See Trial Lecture.

Adjudication committee

  • First opponent: Professor Alberto Ascherio, Department of Nutrition Harvard THC Chan School of Public Health, US
  • Second opponent: Associate professor Marte Bjørk, Department of Clinical Medicine, Faculty of Medicine, University of Bergen
  • Third member and chair of the evaluation committee: Professor Anne Eskild, Institute of Clinical Medicine, University of Oslo

Chair of the Defence

Professor Espen Dietrichs, University of Oslo

Principal Supervisor

Professor Trygve Holmøy, University of Oslo


Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease where loss of motor neurons in affected individuals leads to progressive muscle weakness and respiratory failure. Disease burden is substantial, and causes are largely veiled.

The aim of this thesis was first to describe ALS mortality and prevalence. We validated data from the Norwegian Cause of Death Registry as well as diagnoses given at hospitals. For prevalence, we combined data from the Norwegian Patient Registry, the Norwegian Prescription Database and the Norwegian Cause of Death Registry. Next, we aimed to investigate the temporal relationship between prediagnostic body mass index (BMI), weight change and ALS risk. We designed a cohort study by combining data from a large, near nation-wide tuberculosis mass screening with later health surveys and current compulsory registers.

The death registry was a valid source for detecting ALS deaths, with mortality serving as a good proxy for incidence. ALS mortality increased steadily from 1951 to 2014 when it was 2.7/100,000 person years. An age-period-cohort analysis suggested influences from both improvement in case ascertainment and differential impact from environmental factors across birth cohorts.

Prevalence ranged from 6.9 to 7.7/100,000 population between 2009 and 2015. Comparing prevalence to mortality data suggested differences in survival after diagnosis across genders and regions.

Our cohort study comprised nearly 1.5 million citizens, with nearly 3000 ALS cases and up to 54 years of follow up. High BMI and weight gain were associated with low ALS risk several decades later. Overall, hazard ratio for ALS per 5-unit increase in prediagnostic BMI was 0.83 (95% confidence interval 0.79–0.88).

Taken together, these studies show that existing Norwegian health registers and databases can work as valid sources for ALS disease surveillance, and can detect both trends in disease rates and possible risk factors.

Additional information

Contact the research support staff.





Published Jan. 29, 2020 9:20 AM - Last modified Jan. 29, 2020 9:43 AM