The hidden variables problem in Alzheimer's disease clinical trial design

Abstract

As the leading cause of dementia worldwide, Alzheimer's disease has garnered intense academic and clinical interest. Yet, trials in search of a disease-modifying therapy have failed overwhelmingly. We suggest that, in part, this may be attributable to the influence of disruptive variables inherent to the framework of a clinical trial. Specifically, we observe that everyday factors such as diet, education, mental exertion, leisure participation, multilingualism, sleep, trauma, and physical activity, as well as clinical/study parameters including environment, family coaching, concurrent medications, and illnesses may serve as potent confounders, disruptors, or sources of bias to an otherwise significant drug-disease interaction. This perspective briefly summarizes the potential influence of these hidden variables on the outcomes of clinical trials and suggests strategies to abate their impact.

The efficacy of exergaming in people with major neurocognitive disorder residing in long-term care facilities: a pilot randomized controlled trial

“…Seventh, we did not include a physically active control condition such as a combined aerobic, balance, and strength training program. Eighth, we did not control for the effect of concurrent medication use including for example cholinesterase inhibitors, memantine, typical and atypical antipsychotics, antidepressants, and benzodiazepines, although it is known they may act as potential confounders and disruptors in MNCD trials [ 95 ].…”

Independent replication of advanced brain age in mild cognitive impairment and dementia: detection of future cognitive dysfunction

“…Many clinical trials for AD have failed [ 33 ], and this may, in part, be attributable to heterogeneous pathology and varying lifestyle and medical factors (e.g. diet, education, mental exertion, leisure participation, multilingualism, sleep, trauma, physical activity, concurrent medications and illnesses) [ 34 ]. It has been suggested that future clinical evaluation of AD therapeutics should consider the potential impact of these variables [ 34 ], and brain age may act as a holistic measure of multiple processes that converge on neurodegeneration in various ways.…”

The brains of aged mice are characterized by altered tissue diffusion properties and cerebral microbleeds

“…In the longitudinal study by Maheswaran et al which included transgenic and WT mice, it was found that the WT mouse brain enlarged from 6 to 14 mo, including the whole brain volume, ventricles, and white matter, whereas grey-matter rich regions declined [31]. Of note, studies of aging in mice is well justified because of the access to tissues, the potential for transgenic comparisons, and the lower cost, compared to human studies that require huge study inclusion numbers and an entire lifespan to rule out confounding factors [44]. The objective of this study was to determine features of vascular brain aging in middle-aged and old C57BL/6J mice, a common WT strain used for brain research studies, and to compare and optimize MRI methods with results indicative of brain age.…”