Medical records are used to track events and transactions between patients and health care providers. They offer information on diagnoses, procedures, lab tests, and other services. Medical records help us measure and analyze trends in health care use, patient characteristics, and quality of care.

Electronic health records (EHRs) were first introduced in the 1960s, but only became popular in the 2000s¹, in part due to the American Recovery and Reinvestment Act and the Affordable Care Act. EHRs can make it easier for providers to enter information about patients. The data from EHRs can then be used for research, like comparing how effective providers are, and seeing how patients respond to treatment. In the U.S., patient privacy is still protected even with the use of EHRs by the Health Insurance Portability and Accountability Act (HIPAA), enforced by the Office for Civil Rights (OCR) of the HHS.

Medical records are usually accurate and detailed because they come from health care providers. The data are automatically collected, including information that patients might not think to add or feel comfortable sharing through other data sources like surveys. Because the information is written down in a specific context, however, it can be misinterpreted if taken out of context. And of course, medical records are (by definition) only available for people who are able to get medical care. For researchers, it can be costly, both in time and in money, to obtain medical records in the United States, especially for large-scale studies. This is why surveys are often relied upon to collect information.

This chart shows the hospital discharges by first-listed diagnosis among children in the United States from 1990–2010. This information is gained from medical records.²

*Figure does not meet standards of reliability or precision. Estimates preceded by the asterisk should be used with caution.

Diagnosis	All ages	0–17	0–4	5–17	5–9	10–17
All Diagnoses	1,165.3	337.6	585.1	238.6	167.2	283.8
Infectious and parasitic diseases	42.7	16.7	*	7.3	8.3	6.7
Septicemia	24.5	1.8	4.4	*	*	*
Cancer, all	41.6	*	*	*	*	*
Endocrine, nutritional, and metabolic disorders	59.3	18.9	*	12.4	11.1	13.2
Diabetes	21.2	3.9	*	5.0	*	6.3
Dehydration	10.9	9.1	23.3	3.3	4.7	2.5
Anemias	13.4	4.0	4.2	4.0	2.6	4.9
Mental disorders	68.2	32.0	*	44.0	12.6	63.8
Alcohol and drug	14.4	1.5	*	2.1	*	3.4
Nervous system disorders	33.0	15.8<	28.0	*	10.8	*
Circulatory system disorders	197.3	*	*	*	*	*
Heart disease	127.9	*	*	*	*	*
Arrhythmias	26.1	0.6	*	*	*	*
Heart failure	33.8	*	*	*	*	*
Respiratory system disorders	116.0	73.4	183.8	29.3	42.8	20.8
Acute bronchitis and bronchiolitis	5.5	15.8	54.2	*	*	*
Pneumonia	38.2	21.8	53.9	9.0	14.8	5.3
Asthma	14.9	18.5	36.2	11.4	17.9	7.2
Digestive system disorders	114.7	29.2	38.1	25.7	*	28.6
Appendicitis	9.3	10.4	*	13.5	*	14.2
Inflammatory bowel disease	3.2	0.8	*	1.1	*	1.6
Intestinal obstruction without mention of hernia	11.3	1.8	*	*	*	*
Genitourinary system disorders	69.6	11.2	19.1	8.0	6.1	9.1
Kidney disease	18.3	1.3	*	1.1	*	*
Urinary tract infection	17.9	2.9	7.7	1.0	*	0.9
Cellulitis and abscess	22.8	10.0	21.1	5.6	6.0	5.3
Musculoskeletal system and connective tissues disorders	72.6	5.9	3.7	6.8	4.2	8.5
Injuries and poisoning	64.7	24.7	25.6	24.4	14.9	30.3
Fracture	36.1	10.6	9.8	10.9	8.0	12.7
Certain complications of surgical and medical care	34.2	5.3	7.7	*	*	4.5

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1. Office of the National Coordinator for Health Information Technology. 'Office-based Physician Electronic Health Record Adoption,' Health IT Quick-Stat #50. https://www.healthit.gov/data/quickstats/office-based-physician-electronic-health-record-adoption.

2. "Hospital discharges by first-listed diagnosis among children: US, 1990-2010.". Centers for Disease Control and Prevention. National Center for Health Statistics. Health Data.