If any human ever got close to a magnetar, they would quickly find themselves in dire straits. “Strong magnetic fields can start to do surprising things,” says Sutter. At the atomic level, the strong magnetic field would move all of the positive charges in your body in one direction and the negative charges the other way, he explains; spherical atoms would stretch out into ellipses and soon they would start to resemble thin pencils. That drastic change in shape would interfere with basic chemistry, causing the normal forces and interactions between atoms and molecules in the body to break down. “The first thing you would notice is your entire nervous system, which is based on electrical charges moving throughout your body, is going to stop working,” says Sutter. “And then you basically dissolve.” Sutter guarantees that our local neighborhood — which he defines as a radius of a few hundred light-years around Earth — has been surveyed and certified magnetar-free. None of these exotic objects are approaching us, and none of the massive stars nearby are likely to turn into magnetars when they die. The nearest magnetar is a safe distance of tens of thousands of light-years away. So, at least for the time being, we can rest easy and take comfort in our planet’s own meager magnetic field.
What does that have to do with the price of tea in China? MRI [Magnetic Resonance Imaging] uses magnetic fields between 0.3 and 1.5 million x the strength of the earth's magnetic field.
The real problem is the unimaginably great distances required for interstellar travel. Not many humans are set up to travel for 30 thousand years or 30 million.
It does talk about possible effects of magnetic fields on humans. And, during an MRI, there is a litany of issues that must be mitigated prior to the procedure. A medical implant can be effected by an MRI but I don't know the maximum level of magnetism that can be tolerated by medical implants, medication pumps, clips and rods and screws, etc. and how this might correlate to magnetic fields in space or on other planets? I doubt we know the effects on humans of long-term exposure to varying magnetic fields...
Most all space travel of great distances are going to be one-way tickets. Unless new physics arrives for much faster space travel, it will take thousands of generations to get anywhere...