The proportion of older people in the world population is expected to increase rapidly during the upcoming decades. Consequently, the number of patients with multimorbidity will increase dramatically. In epidemiologic research, the concepts of multimorbidity, comorbidity, and complications have been confusing, and some of these concepts are used interchangeably. In this commentary, the authors propose a clear terminology for clinical concepts describing different aspects of multimorbidity and elucidate the relationship between these clinical concepts and their epidemiologic analogs. Depending on whether a study uses causal or predictive models, a proper distinction between concepts of multimorbidity is important. It can be very difficult to separate complications of the index disease under study from comorbidity. In this context, use of comorbidity indices as confounding scores should be done with caution. Other methodologic issues are type, duration, severity, and number of comorbidities included in the ascertainment methods, as well as sources included in the research. Studies that recognize these challenges have the potential to yield valid estimates of the comorbidity burden and results that can be compared with other studies.

Background and Purpose Stroke is a risk factor for dementia, but the risk of dementia after different stroke types is poorly understood. We examined the long-term risk of dementia among survivors of any first-time stroke and of first-time ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage. Methods We conducted a 30-year nationwide population-based cohort study using data from Danish medical databases (1982–2013) covering all Danish hospitals. We identified 84,220 ischemic stroke survivors, 16,723 intracerebral hemorrhage survivors, 9,872 subarachnoid hemorrhage survivors, and 104,303 survivors of unspecified stroke types. Patients were aged ≥18 years and survived for at least three months after diagnosis. We formed a comparison cohort from the general population (1,075,588 patients without stroke, matched to stroke patients by age and sex). We computed absolute risks and hazard ratios of dementia up to 30 years after stroke. Results The 30-year absolute risk of dementia among stroke survivors was 11.5% (95% confidence interval, 11.2%–11.7%). Compared with the general population, the hazard ratio (95% confidence interval) for dementia among stroke survivors was 1.80 (1.77–1.84) after any stroke, 1.72 (1.66–1.77) after ischemic stroke, 2.70 (2.53–2.89) after intracerebral hemorrhage, and 2.74 (2.45–3.06) after subarachnoid hemorrhage. Younger patients regardless of stroke type faced higher risks of post-stroke dementia than older patients. The pattern of hazard ratios by stroke type did not change during follow-up and was not altered appreciably by age, sex, or preexisting diagnoses of vascular conditions. Conclusions Stroke increases dementia risk. Survivors of intracerebral hemorrhage and subarachnoid hemorrhage are at particularly high long-term risk of post-stroke dementia.

Aims The association between heart failure and dementia remains unclear. We assessed the risk of dementia among patients with heart failure and members of a general population comparison cohort. Methods and results Individual-level data from Danish medical registries were linked in this nationwide population-based cohort study comparing patients with a first-time hospitalization for heart failure between 1980 and 2012 and a year of birth-, sex- and calendar-year matched comparison cohort from the general population. Stratified Cox regression analysis was used to compute 1–35-year hazard ratios (HRs) for the risk of all-cause dementia and, secondarily, Alzheimer’s disease, vascular dementia, and other dementias. Analyses included 324,418 heart failure patients and 1,622,079 individuals from the general population (median age = 77 years, 52% male). Compared with the general population cohort, risk of all-cause dementia was increased among heart failure patients, adjusted HR: 1.21, 95% confidence interval (CI), 1.18–1.24. The associations were stronger in men and in heart failure patients under age 70. Heart failure patients had higher risks of vascular dementia (adjusted HR: 1.49, 95% CI, 1.40–1.59) and other dementias (adjusted HR: 1.30, 95% CI, 1.26–1.34) than members of the general population cohort. Heart failure was not associated with Alzheimer’s disease (adjusted HR: 1.00, 95% CI, 0.96–1.04). Conclusion Heart failure was associated with an increased risk of all-cause dementia. Heart failure may represent a risk factor for dementia, but not for Alzheimer’s disease.

Coexisting cancer in patients with atrial fibrillation (AF) has been associated with thromboembolism and bleeding. We used Danish population‐based medical databases to conduct a population‐based cohort study that included all AF patients who redeemed a prescription for vitamin K antagonists (VKA) or non‐VKA oral anticoagulant (NOAC) between July 2004 and December 2013. We characterized these patients according to the presence (N = 11,855) or absence (N = 56,264) of a cancer diagnosis before redemption of their oral anticoagulant prescription, and then examined their 1‐year risk of thromboembolic or bleeding complications or death. We next used Cox regression to compare the hazard ratios for complications among VKA‐ or NOAC‐treated AF patients with versus without a cancer diagnosis, after adjusting for sex, age, and CHA2DS2 VASc score. One‐year risks of thromboembolic complications in AF patients who redeemed a VKA prescription were similar in those with (6.5%) and without (5.8%) cancer [hazard ratio (HR) 1.0 (95% confidence interval (CI): 0.93, 1.1)]. This also was found for bleeding complications (5.4% vs. 4.3%, HR 1.1 [95% CI: 1.0, 1.2]). For AF patients with cancer who redeemed a NOAC prescription, risks were also similar for thromboembolic complications (4.9% of cancer patients vs. 5.1% of noncancer patients, HR 0.80 [95% CI: 0.61, 1.1]), and for bleeding complications (4.4% vs. 3.1%, HR 1.2 [95% CI: 0.92, 1.7]). The absolute risks of thromboembolic or bleeding complications were nearly the same in patients with and without cancer who redeemed prescription for VKAs or NOACs.