NIS & real-world data.

Answer national-scale clinical questions with data on millions of real hospital admissions, outcomes, trends, disparities, and resource use, without recruiting a single patient. Built on the largest publicly available inpatient database in the United States.

What it is

Millions of real admissions, one national picture.

The National Inpatient Sample (NIS), part of the AHRQ Healthcare Cost and Utilization Project (HCUP), is the largest publicly available all-payer inpatient care database in the US. It is a stratified ~20% sample of discharges from community hospitals, weighted to represent more than 35 million hospitalizations a year, each coded with ICD diagnoses and procedures.

What it can and cannot do

Strength, national, representative estimates from millions of admissions.

Design, retrospective cross-sectional and trend (serial cross-sectional) analyses.

Limits, it counts encounters, not unique patients, and has no post-discharge follow-up.

How it works

The method, in plain terms.

01

Define the cohort

ICD-10-CM/PCS codes

02

Survey weights

20% sample → national estimates

03

Outcomes & covariates

Mortality, LOS, cost, comorbidity

04

Trends

Joinpoint across years

05

Risk adjustment

Multivariable, propensity

06

Reporting

HCUP rules, honest caveats

How you benefit

Why authors start here.

The project, step by step

How an NIS study runs with Cohira.

Start an NIS study →

1

Scope the question

We refine your idea into a national question NIS can actually answer, and confirm the codes exist.

2

Cohort & codes

We define the ICD-based cohort, comparators, outcomes, and covariates in a pre-specified plan.

3

Data & weighting

We obtain the relevant NIS years and apply the correct survey weights and design.

4

Analysis

We run weighted, risk-adjusted analyses in R or Stata, with trend and sensitivity checks.

5

Manuscript

We draft a clear paper with you, tables, trend figures, and an honest limitations section.

6

Submit & revise

We target the right journal, submit, and answer reviewers with you through to a decision.

Published examples

What NIS studies look like in print.

Independent, peer-reviewed examples of what this route can produce.

J Am Heart AssocComparative cohort

Trends in incidence, management, and outcomes of cardiogenic shock complicating STEMI in the United States

Kolte D, et al. · 2014

NIS analysis comparing outcomes across years and treatment strategies in 1.99 million STEMI hospitalisations.

View in journal →
Am J CardiolIllustrative example

Severe obesity and heart failure

Aguilar-Gallardo JS, et al. · 2022

Across 2.4 million heart-failure admissions, the obesity-survival paradox held for non-severe but not severe obesity.

View in journal →
JACC Cardiovasc IntervIllustrative example

Temporal trends and outcomes of mechanical complications in acute myocardial infarction

Elbadawi A, et al. · 2019

Analyzed ~9 million MI hospitalizations; mechanical complications were rare but carried roughly 42% mortality after STEMI.

View in journal →
JAMA Network OpenIllustrative example

Pregnancy characteristics and maternal mortality with amniotic fluid embolism

Mazza GR, et al. · 2022

Among 14.7 million deliveries, characterized amniotic fluid embolism risk factors and its 17% failure-to-rescue mortality.

View in journal →

These are independent published studies, shown to illustrate what the NIS makes possible, they are not Cohira's work. We help you design and publish studies of comparable rigor.

Pricing

One fee, from idea to publication.

Database study, idea to publication
Protocol, analysis with reproducible code, manuscript, journal shortlist, submission, and reviewer responses.
$1,800per study

Per project, never per author. Journal fees and database access are billed at cost. Your week-by-week timeline is written into the free feasibility note before you pay. Booking more than one study? 10% off the second, 15% off from the third. Acceptance Guarantee & group pricing →

More study types

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Start a conversation

Have a national question to answer?

Tell us the outcome or trend you care about. We will tell you honestly whether NIS can support a strong paper, and how we would build it.

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