a study published in tuesday 's journal of the american medical association revealed the figures .
almost 30 million health records nationwide were involved in criminal theft , malicious hacking or other data breaches over four years .
compromised information included patients ' names , home addresses , ages , illnesses , test results or social security numbers .
most involved electronic data and theft , including stolen laptops and computer thumb drives .
cyber-security experts say thieves may try to use patients ' personal information to fraudulently obtain medical services .