Long-term risk of dementia following hospitalization due to physical diseases: A multicohort study

Abstract

Introduction: Conventional risk factors targeted by prevention (e.g., low education, smoking, and obesity) are associated with a 1.2- to 2-fold increased risk of dementia. It is unclear whether having a physical disease is an equally important risk factor for dementia.

Methods: In this exploratory multicohort study of 283,414 community-dwelling participants, we examined 22 common hospital-treated physical diseases as risk factors for dementia.

Results: During a median follow-up of 19 years, a total of 3416 participants developed dementia. Those who had erysipelas (hazard ratio = 1.82; 95% confidence interval = 1.53 to 2.17), hypothyroidism (1.94; 1.59 to 2.38), myocardial infarction (1.41; 1.20 to 1.64), ischemic heart disease (1.32; 1.18 to 1.49), cerebral infarction (2.44; 2.14 to 2.77), duodenal ulcers (1.88; 1.42 to 2.49), gastritis and duodenitis (1.82; 1.46 to 2.27), or osteoporosis (2.38; 1.75 to 3.23) were at a significantly increased risk of dementia. These associations were not explained by conventional risk factors or reverse causation.

Discussion: In addition to conventional risk factors, several physical diseases may increase the long-term risk of dementia.

Keywords: cohort studies; dementia; disease; hospitalization; risk factors.

FIGURE 1

Hazard ratios for incident dementia by exposure to 22 hospital‐treated diseases in main analysis (full follow‐up) and in sensitivity analysis (the first 10 years of dementia follow‐up excluded). ICD‐10, International Classification of Diseases, 10th Revision. The bars represent 95% confidence intervals. Age is the time scale and hazard ratios are adjusted for sex (hyperplasia of prostate was analyzed in men only). Within‐study clustering of participants has been taken into account using cohort‐specific baseline hazards and cohort‐specific adjustment terms for sex. *Significant association in the main analysis after Bonferroni correction for 22 tests (P < .0023). ^†Significant association after Bonferroni correction in the main analysis and significant association (P < .05) in the sensitivity analysis excluding first 10 years of dementia follow‐up.

FIGURE 2

Hazard ratio for dementia for conventional risk factors versus physical diseases. The bars represent 95% confidence intervals. Numerical estimates are reported in Table A.6 in the Appendix and their references are provided in the Appendix (p. 99). Our estimates for physical diseases are the same as those from full dementia follow‐up in Figure 1. The low and high estimates for the hazard ratios for conventional risk factors are from 16 meta‐analyses.

FIGURE 3

Hazard ratio for early onset and late‐onset dementia by exposure to eight physical diseases. ICD‐10, International Classification of Diseases, 10th Revision. The bars represent 95% confidence intervals. Age is the time scale and hazard ratios are adjusted for sex. The within‐study clustering of participants has been taken into account using cohort‐specific baseline hazards and cohort‐specific adjustment terms for sex.