Risk of Dementia in Non-Overtly Functional Adrenal Tumours (NOFAT)-Reply.
Description:We express our gratitude for the insightful commentary by Dr Notarianni on our study. As accurately pointed out, in all patients with non-overtly functional adrenal tumours (NOFATs) diagnosed in Sweden between 2005 and 2019 (n = 20,390) the prevalence of unspecified dementia, Alzheimer's disease (AD) and vascular dementia (VD) were reduced compared to controls without diagnosed adrenal tumours (n = 125,392) [1]. This is probably because individuals diagnosed with dementia tend to undergo imaging less frequently. Moreover, the incidence of new unspecified dementia, AD and VD was similar as controls during the follow-up period up (median 4.9 years, IQR 2.2–8.2). However, it is important to note that these were diagnosed cases of dementia, and many cases of mild dementia may go undiagnosed. We appreciate the thorough analysis and the opportunity to address some of the important points raised by Dr Notarianni regarding the potential role of the apolipoprotein E (APOE) genotype as a confounding factor. The APOE ε4 allele is a well-established risk factor for dementia, particularly AD and VD. APOE ε4 has also been associated with an atherogenic lipid profile, which increases the risk of cerebrovascular disease, a key contributor to vascular dementia [2]. Recent research further supports that APOE variants influence various forms of vascular disease. For instance, a study by Rasmussen et al. demonstrated that APOE carriers exhibit increased risk of ischaemic cerebrovascular disease, highlighting the complex interplay between APOE genotype and cerebrovascular pathology [3]. APOE polymorphisms were found to influence lipid metabolism, with the ε4 allele being associated with higher levels of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) while reducing high-density lipoprotein cholesterol (HDL-C). Furthermore, ε4 acted as an independent risk factor for both cancer and cardiovascular disease [4]. These findings align with previous research suggesting that the APOE ε4 genotype contributes to both metabolic and vascular risk factors that may influence dementia development. However, in our register-based study, we did not have access to genetic data for either cases or controls, limiting our ability to directly analyse APOE allele distributions. We assumed similar APOE distributions in both groups, but we acknowledge that if there were significant differences, this could have influenced our findings. To mitigate this, we accounted for key cardiometabolic confounders, such as hyperlipidaemia and atherosclerotic heart disease, in our statistical models. Given the well-documented links between APOE and lipid metabolism, this approach may have helped address some of the potential confounding effects. Additionally, studies have linked APOE ε4 to an increased risk of tumorigenesis and cardiovascular disease [4]. While the relationship between APOE and adrenal tumours has not been explicitly studied, there is evidence suggesting that adrenal tumours, particularly NOFATs, also carry an increased baseline risk of tumorigenesis. Patrova et al. reported that patients with NOFATs exhibited increased overall mortality, including from cardiovascular disease and cancer, with a more pronounced effect in younger individuals [5]. Future studies exploring this intersection may provide valuable insights into shared pathways linking APOE, adrenal function, and dementia risk. In conclusion, while our study found no increased risk of dementia in patients with NOFATs, we recognise that APOE genotype could be an important variable. We contend that prospective studies incorporating genomic data would prove invaluable in further delineating these associations. We reiterate our appreciation for the thoughtful feedback and for contributing to this important discussion.









