Prolonged endurance exercise is associated with an elevated risk of atrial fibrillation (AF). The mechanisms governing this increased risk remains elusive. This study aim to detail the specific traits of elderly subjects with AF conducting endurance training by comparing elderly participators in the Birkebeiner cross country ski race(an indicator of prolonged endurance exercise practice) with and without AF to a not-so-trained control group.

In recent years endurance sports with high intensity and participation in competition have been increasingly popular among middle aged and older people. The Birkebeiner studies are investigations of elderly non-professional athletes (65 years or older at enrollment in 2009/10) participating in the Birkebeiner cross-country ski race. It consists of Birkebeiner Aging Study, BIAS and the Birkebeiner Atrial Fibrillation, (BAF-study). The BAF-study investigated the association between prolonged endurance sport practice and the risk of AF by comparing the cohort of veteran cross-country skiers to a control population drawn from the Health and Environment Study in Oslo (HELMILO 2009).

The main findings of the Birkebeiner study so far have been that participation in the Birkebeiner cross-country ski race (an indicator of prolonged endurance exercise practice) is associated with an elevated risk of atrial fibrillation (AF) among men ≥ 65 years, and that this risk correlates with the cumulated amount of endurance-training. Similar findings were seen amongst female athletes. This increased risk of AF was shown independent of other known significant comorbidities (such as hypertension and diabetes), indicating that endurance-training at this level itself is an independent risk factor.

Regular physical exercise is an important factor when it comes to successful ageing. However, dose-relationship of physical exercise in a longer perspective is poorly studied. Atrial fibrillation is associated with increased risk of stroke, heart failure, dementia and death.

The mechanisms governing the increased risk of AF in elderly subjects undergoing endurance-training remains elusive. This study aim to detail the specific traits of elderly subjects with AF conducting endurance-training in comparison with trained and not-so-trained control groups. Thus, generating knowledge that can form the basis for better prevention and treatment of AF in this group.

Inclusion Criteria:

• Already included in the Birkebeiner studies or "Health and environment study in Oslo" (HELMILO)
• Born 1960 and earlier

Exclusion Criteria:

• Born before 1935.
• Earlier heart valve surgery.
• MI (Mitral Insufficiency)≥ grade 3
• Ejection Fraction (EF) <35%

The study population is drawn from earlier Birkebeiner studies and the Control Group from a Health population study in Oslo (HELMILO) matched by age and gender.