Table 4.

Incidence rate ratio (IRR) for postoperative mortality after hip fracture surgery

Variable	30-day mortality IRR (95% CI)	p value
All-cause mortality
No dementia	Ref
Dementia	1.67 (1.60–1.75)	< 0.001
Cause-specific mortality for patients with dementia*
Cardiovascular	1.42 (1.32–1.54)	< 0.001
Respiratory	1.76 (1.57–1.99)	< 0.001
Cerebrovascular**	7.43 (4.99–11.07)	< 0.001
Sepsis	2.17 (1.47–3.22)	< 0.001
Multi-organ failure	1.66 (1.53–1.79)	< 0.001
Unknown***	11.2 (8.06–15.58)	< 0.001

Poisson regression model with robust standard errors. Multiple imputation with chained equations was used to manage missing values. The model is adjusted for age, sex, American Society of Anesthesiologists (ASA) classification, fracture type, type of surgery, prior myocardial infarctions, prior cerebrovascular events, peripheral vascular disease, chronic obstructive pulmonary disease, congestive heart failure, connective tissue diseases, diabetes mellitus, liver disease, chronic kidney disease, as well as local tumor and metastatic carcinoma

^*Reference group is patients without dementia

^**Not adjusted for ASA classification and liver disease due to their inclusion resulting in a matrix that is computationally singular

^***Not adjusted for ASA classification due to its inclusion resulting in a matrix that is computationally singular