Age in days (AGEDAY) is reported for patients less than 1 year old. AGEDAY is calculated from date of birth (DOB) and the admission date (ADATE) with the following exceptions:

• AGEDAY is set to the supplied age in days if the age cannot be calculated (ADATE and/or DOB is missing or invalid).
• AGEDAY is missing (.) if the age cannot be calculated and the reported age in days is missing.
• AGEDAY is missing (.) if the calculated age in years is out of range (AGE NE 0-124).
• AGEDAY is invalid (.A) if the age in days cannot be calculated and the supplied age in days is nonnumeric. An invalid calculated AGEDAY is not replaced by the reported age in days.
• If the data source does not provide the necessary dates to calculate age in days or the reported age in days, then beginning in the 1998 data, AGEDAY is not present on the HCUP files. In the 1988-1997 data, AGEDAY is retained on the HCUP files and is set to unavailable from source (.B).
• AGEDAY is set to inconsistent (.C) if one of the HCUP edit checks is triggered. The age edit checks vary by year.
  • Beginning in the 1998 data, AGEDAY is inconsistent with neonatal diagnoses (EAGE04), or is inconsistent with maternal diagnoses/procedures (EAGE05).
  • In the 1998-1997 data, AGEDAY is inconsistent with AGE (ED021), neonatal diagnoses (ED3nn), maternal diagnoses (ED4nn), or maternal procedures (ED5nn).

When processing the 1996 HCUP inpatient data, no adjustment was made for the leap year when age was calculated from date of birth and admission date. This caused infants admitted on the day before their first birthday to have AGE=1 and AGEDAY = missing (.), instead of AGE=0 and AGEDAY=364.

Only the calculated age in days could be used to assign AGEDAY because Arkansas did not supply this information.

Only the calculated age could be used to assign AGEDAY because Arizona did not supply age in days.

California assigned the date of birth to admission date when the admission date was not reported and the discharge had a principal diagnosis indicating a newborn (defined as DX1 equal to V3x.0x). This caused the calculated age to be 0 days.

Beginning in data year 2014, Colorado no longer supplies age in days. Age in days could not be calculated because the date of birth (DOB) provided by Colorado does not include the day of birth. Only birth month and year are provided. The day of birth was set to 15 for all records.

Prior to 2001, AGEDAY is coded differently in Georgia than in the other HCUP states. Georgia supplied age in days using a mix of days (for patients up to one month old) and 30-day intervals for (patients older than one month):

• Patients age less than 1 month old is coded in days from 0 to 30 (i.e., 0, 1, 2, 3 etc.).
• Patients age between 1 month and 1 year old is coded in 30-day intervals (i.e., 30, 60, 90, 120, etc.)

The maximum value for AGEDAY is 330.

Beginning with the 2001 data, Georgia no longer supplied 30-day intervals for age in days but instead reports a calculated age in days ranging from 0-365.

Beginning in 2000, the reported age in days was used when the age in days could not be calculated from dates. Prior to 2000, only the calculated age could be used to assign AGEDAY. From 1996-1998, Hawaii did not supply age in days. In 1998-1999, Hawaii reported age in days, but the coding was not consistent with the HCUP standard coding.

Beginning in 1998, Hawaii provided the date of birth (DOB) with a four-digit year. In prior years, only a two-digit year was available.

Only the calculated age could be used to assign AGEDAY because Illinois did not supply age in days.

Only the calculated age in days was used to assign AGEDAY.

AGEDAY may be incorrectly set to invalid (.A) on newborn records. When only the year of birth is available, Iowa codes the day and month of birth to '01'. This causes the calculated age in days to be negative, and therefore set to invalid (.A).

Only the calculated age could be used to assign AGEDAY. Prior to 1998, Iowa supplied age in days, but the coding is inconsistent with HCUP standards.

Beginning in 2008, we use supplied fields when we cannot calculate from dates.

Prior to 2008, only the calculated age in days could be used to assign AGEDAY because Kentucky did not supply this information. Beginning 2008, age in days was used to assign AGEDAY.

Prior to 2001, AGEDAY could not be calculated because Michigan did not report admission and birth dates. Beginning with the 2001 data, Michigan provided complete dates and AGEDAY could be calculated.

Only the calculated age in days could be used to assign AGEDAY because Minnesota did not supply this information.

Only the calculated age in days could be used to assign AGEDAY because Nebraska did not supply this information.

Only the calculated age in days was used to assign AGEDAY.

Beginning in 2009, New Jersey supplied age in months.

In 2008, only the calculated age was used to assign AGEDAY because New Jersey did not supply age in days.

Beginning in 2001, the reported Age in Days was used when AGEDAY could not be calculated. Prior to 2001, only the calculated age could be used to assign AGEDAY because New Jersey did not supply age in days.

Beginning with the 2008 data, the HCUP data element AGEDAY is missing (.) for AIDS/HIV patients. New York identifies AIDS/HIV records by ICD-9-CM diagnosis code, DRG, or MS-DRG:

• An admitting, principal or any secondary diagnosis of "042", "043", "044", "7958", "27910", "27919", "2793", "1363", "79571", "07951", "07952", "07953", "V017" or "V08".
• A DRG of 488 through 490 (prior to October 2007) or MS-DRG of 700 through 716 (beginning in October 2007).

Please note that the admitting diagnosis is not retained in the HCUP databases prior to 2012.

In the 1988-1997 HCUP New York databases, the data source provided admission year and month, but did not provide the day. A day of "01" was imputed for all records. The imputed date was not used to calculate other data elements or to perform edit checks. Beginning in 1998, the complete admission date was provided by the data source.

Only the calculated age in days could be used to assign AGEDAY because North Dakota did not supply this information.

Only the calculated age in days could be used to assign AGEDAY because Ohio did not supply this information.

Only the supplied age could be used because Oklahoma does not supply date of birth. Oklahoma reports age in years (AGE) as missing for patients with AGE < 1 and does not report age in days (AGEDAY) for patients with AGE >= 1. During HCUP processing AGE was set to 0 for records with a valid value for age in days (AGEDAY).

During HCUP processing, only the calculated age in days could be used to assign AGEDAY because:

• Oregon did not report age in days in the data prior to 1998 and
• Oregon reported age in days at discharge beginning in the 1998 data.

Beginning in 2007, reported age in days was used if the calculated age in days was missing.

Beginning in 1993, only the calculated age in days could be used to assign AGEDAY:

• In 1993, the source used the same code (zero days) to report the age of newborns and missing values.
• Beginning in 1994, the source supplied age group categories rather than reporting age in days.

Beginning in 2008, only the supplied age in days could be used to assign AGEDAY because Pennsylvania did not provide date of birth.

Only the calculated age in days could be used to assign AGEDAY because Rhode Island did not supply this information.

Prior to 2008, only the calculated age could be used to assign AGEDAY because Tennessee did not supply age in days.

Only the calculated age could be used to assign AGEDAY because Utah did not supply age in days.

Only the calculated age in days could be used to assign AGEDAY because Vermont did not supply this information.

Age in days could not be calculated from dates since Virginia did not report the date of birth. During HCUP processing, only the reported age in days could be used to assign AGEDAY.

Only the calculated age in days could be used to assign AGEDAY because West Virginia did not supply this information.