Researchers detected a dose-response relationship between the number of fires firefighters battled and their risk of heart problems, which is considered a strong indicator of a causal relationship.
Powerful magnets found in many portable electronic devices could disable some functions of pacemakers and heart defibrillators.
Wired pacemaker leads have been plagued with problems over the years.
Researchers warn that individuals should not stop taking omega-3 fish oil supplements until they talk to their doctor about the risk of abnormal heart rhythms.
