Short term use of nicotine patches is okay and not dangerous and can help you quit smoking cigarettes.
However yes long term use of nicotine patches can cause more harm to your health than the cigarettes could cause to your health.
Longer term use of nicotine patches can increase your dosage of nicotine to possibly deadly levels which can cause cancer, heart attacks and heart disease and possibly a stroke.
So if you need to use nicotine patches to quit smoking you should avoid using the nicotine patches for too long and only use the nicotine patches short term to avoid any other health issues.
If you experience any other health issues when using the nicotine patches then you should speak with your doctor because you might need to stop using the nicotine patches for awhile.