Table. Change in Rates of Hospitalization and Observation Stays Related to Overall, Acute, and Chronic ACSCs^a.

Admission Status by ACSC Category	Year		Yearly Change, Slope (95% CI)	P Value for Trend
	2011	2015
All ACSCs, No. per 100 000 Medicare beneficiaries
Hospitalization	5517	4158	−326.2 (−332.8 to −319.7)	<.001
Observation	3743	4718	245.6 (233.4 to 257.7)	<.001
Chronic ACSCs, No. per 100 000 Medicare beneficiariesb
Hospitalization	3055	2340	−167.8 (−172.9 to −162.7)	<.001
Observation	2617	3350	188.6 (178.5 to 198.7)	.001
Acute ACSCs, No. per 100 000 Medicare beneficiariesc
Hospitalization	2463	1819	−158.4 (−162.4 to −154.4)	<.001
Observation	1126	1368	57.0 (51.7 to 62.3)	<.001

Abbreviation: ACSCs, ambulatory care–sensitive conditions.

^aMultivariable linear regression models were used to estimate yearly hospitalization rates and observation stays by using a 20% national sample of Medicare inpatient and outpatient data for 2011 to 2015 after adjusting for patient demographics and comorbidities, and treating time as a categorical variable. Yearly slopes were estimated by treating time as a continuous variable. All models included HRR fixed effects. The study baseline was 2011, and 2015 was the latest year for which relevant national data were available.

^bChronic ACSCs included short-term and long-term complications of diabetes, uncontrolled diabetes, lower extremity amputation related to diabetes, asthma in adults, chronic obstructive pulmonary disease, hypertension, heart failure, and angina without procedure.

^cAcute ACSCs included dehydration, bacterial pneumonia, urinary tract infection, and perforated appendix.