Table 4.

Association between the number of common infections and dementia

	Total number of incident dementia diagnoses	Total person-years at risk	Age-adjusted HR (95% CI)*	Age, sex, IMD, and calendar period adjusted HR (95% CI)†	Fully adjusted HR (95% CI)‡
No infection	25 314	3 895 425	1 (ref)	1 (ref)	1 (ref)
First infection	11 209	859 035	1·52 (1·49–1·55)	1·42 (1·39–1·45)	1·34 (1·32–1·37)
Second and additional infections§	14 112	731 026	1·04 (1·03–1·04)¶	1·02 (1·02–1·03)¶	1·02 (1·01–1·02)¶

HR=hazard ratio. IMD=Index of multiple deprivation.

^*Age as the underlying timescale.

^†Adjusted for age, sex, patient level IMD, and calendar time period over follow-up (2004–08, 2009–13, and 2014–18).

^‡Adjusted for age, sex, patient level IMD, and calendar time period over follow-up (2004–08, 2009–13, and 2014–18), ethnicity, smoking status, heavy alcohol consumption, anxiety and depression, severe mental illness, inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, psoriasis, asthma, chronic kidney disease, chronic liver disease, chronic obstructive pulmonary disease, diabetes mellitus, heart failure, hypertension, obstructive sleep apnoea, stroke, traumatic brain injury, benzodiazepines, proton pump inhibitors, systemic corticosteroids, and polypharmacy.

^§Quantitative variable of number of infections from a count of two or more infections alongside a binary variable for yes or no infections in all models. Likelihood ratio test for trend, p<0·0001 in fully adjusted model.

^¶Per additional infection.