Do prenatal factors shape the risk for dementia?: A systematic review of the epidemiological evidence for the prenatal origins of dementia

How Can Early Stress Influence Later Alzheimer's Disease Risk? Possible Mediators and Underlying Mechanisms

Alzheimer's disease (AD) is a progressive, age-related neurodegenerative disorder to which genetic mutations and risk factors contribute. Evidence is increasing that environmental and lifestyle-related factors, such as exercise, nutrition, education, and exposure to (early-life) stress modify the onset, incidence, and progression of AD. Here, we discuss recent preclinical findings on putative substrates that can explain or contribute to the effects of stress early in life on the risk of developing AD. We focus in particular on stress hormones, neural networks, synapses, mitochondria, nutrient and lipid metabolism, adult neurogenesis, engram cell ensembles, and neuroinflammation. We discuss the idea that stress exposure early in life can alter these processes, either combined or in isolation, thereby reducing the capacity of the brain to resist deleterious consequences of, for example, amyloid-β accumulation, thereby accelerating cognitive decline and progression of Alzheimer-related changes in model systems of the disease. A better understanding of whether experiences early in life also modify trajectories of cognitive decline and pathology in AD and how the substrates discussed translate to humans may help develop novel preventive and/or therapeutic strategies to mitigate the consequences of stressors early in life and increase resilience to developing dementia.

Prenatal exposure to undernutrition is associated with a specific lipid profile predicting future brain aging

Prenatal adversity affects cognitive and brain aging. Both lipid and leptin concentrations may be involved. We investigated if prenatal undernutrition is associated with a specific blood lipid profile and/or leptin concentrations, and if these relate to cognitive function and brain aging. 801 plasma samples of members of the Dutch famine birth cohort were assessed for lipidomics and leptin at age 58. Cognitive performance was measured with a Stroop task at 58, and MRI-based BrainAGE was derived in a subsample at 68. Out of 259 lipid signals, a signature of five identified individuals who were undernourished prenatally. These five lipids were not associated with cognitive performance, but three were predictive of BrainAGE. Leptin was not associated with prenatal famine exposure, Stroop performance, or BrainAGE. In conclusion, prenatal undernutrition was associated with an altered lipid profile predictive of BrainAGE 10 years later, demonstrating the potential of lipid profiles as early biomarkers for accelerated brain aging.

Low birthweight in patients with type 2 diabetes is associated with elevated risk of cardiovascular events and mortality

AIMS/HYPOTHESIS

Low birthweight is a risk factor for type 2 diabetes and CVD. This prospective cohort study investigated whether lower birthweight increases CVD risk after diagnosis of type 2 diabetes.

METHODS

Original midwife records were evaluated for 8417 participants recently diagnosed with type 2 diabetes in the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) cohort. Patients were followed for the first occurrence of a composite CVD endpoint (myocardial infarction, coronary revascularisation, peripheral arterial disease, stroke, unstable angina, heart failure or CVD death), a three-component endpoint comprising major adverse cardiovascular events (MACE), and all-cause mortality. Ten-year risks were estimated using the Aalen-Johansen estimator considering non-CVD death as a competing risk. HRs were determined by Cox regression. Models were controlled for sex, age, calendar year at birth, family history of diabetes and born-at-term status.

RESULTS

A total of 1187 composite CVD endpoints, 931 MACE, and 1094 deaths occurred during a median follow-up period of 8.5 years. The 10-year standardised composite CVD risk was 19.8% in participants with a birthweight <3000 g compared with 16.9% in participants with a birthweight of 3000-3700 g, yielding a risk difference (RD) of 2.9% (95% CI 0.4, 5.4) and an adjusted HR of 1.20 (95% CI 1.03, 1.40). The 10-year MACE risk for birthweight <3000 g was similarly elevated (RD 2.4%; 95% CI 0.1, 4.7; HR 1.22; 95% CI 1.01, 1.46). The elevated CVD risk was primarily driven by stroke, peripheral arterial disease and CVD death. All-cause mortality showed no substantial difference.

CONCLUSIONS/INTERPRETATION

Having a birthweight <3000 g is associated with higher CVD risk among patients with type 2 diabetes, driven primarily by risk of stroke and CVD death.

Charting Alzheimer's Disease and Dementia: Epidemiological Insights, Risk Factors and Prevention Pathways

Alzheimer's disease (AD), the most common cause of dementia, is a complex and multifactorial condition without cure at present. The latest treatments, based on anti-amyloid monoclonal antibodies, have only a modest effect in reducing the progression of cognitive decline in AD, whereas the possibility of preventing AD has become a crucial area of research. In fact, recent studies have observed a decrease in dementia incidence in developed regions such as the US and Europe. However, these trends have not been mirrored in non-Western countries (Japan or China), and the contributing factors of this reduction remain unclear. The Lancet Commission has delineated a constrained classification of 12 risk factors across different life stages. Nevertheless, the scientific literature has pointed to over 200 factors-including sociodemographic, medical, psychological, and sociocultural conditions-related to the development of dementia/AD. This narrative review aims to synthesize the risk/protective factors of dementia/AD. Essentially, we found that risk/protective factors vary between individuals and populations, complicating the creation of a unified prevention strategy. Moreover, dementia/AD explanatory mechanisms involve a diverse array of genetic and environmental factors that interact from the early stages of life. In the future, studies across different population-based cohorts are essential to validate risk/protective factors of dementia. This evidence would help develop public health policies to decrease the incidence of dementia.

Aging, sex, metabolic and life experience factors: Contributions to neuro-inflammaging in Alzheimer's disease research

Alzheimer's disease (AD) is prevalent around the world, yet our understanding of the disease is still very limited. Recent work suggests that the cornerstone of AD may include the inflammation that accompanies it. Failure of a normal pro-inflammatory immune response to resolve may lead to persistent central inflammation that contributes to unsuccessful clearance of amyloid-beta plaques as they form, neuronal death, and ultimately cognitive decline. Individual metabolic, and dietary (lipid) profiles can differentially regulate this inflammatory process with aging, obesity, poor diet, early life stress and other inflammatory factors contributing to a greater risk of developing AD. Here, we integrate evidence for the interface between these factors, and how they contribute to a pro-inflammatory brain milieu. In particular, we discuss the importance of appropriate polyunsaturated fatty acids (PUFA) in the diet for the metabolism of specialised pro-resolving mediators (SPMs); raising the possibility for dietary strategies to improve AD outlook.

Controversial Past, Splendid Present, Unpredictable Future: A Brief Review of Alzheimer Disease History

Background: The concept of Alzheimer disease (AD)-since its histological discovery by Alzheimer to the present day-has undergone substantial modifications. Methods: We conducted a classical narrative review of this field with a bibliography selection (giving preference to Medline best match). Results: The following subjects are reviewed and discussed: Alzheimer's discovery, Kraepelin's creation of a new disease that was a rare condition until the 1970's, the growing interest and investment in AD as a major killer in a society with a large elderly population in the second half of the 20th century, the consolidation of the AD clinicopathological model, and the modern AD nosology based on the dominant amyloid hypothesis among many others. In the 21st century, the development of AD biomarkers has supported a novel biological definition of AD, although the proposed therapies have failed to cure this disease. The incidence of dementia/AD has shown a decrease in affluent countries (possibly due to control of risk factors), and mixed dementia has been established as the most frequent etiology in the oldest old. Conclusions: The current concept of AD lacks unanimity. Many hypotheses attempt to explain its complex physiopathology entwined with aging, and the dominant amyloid cascade has yielded poor therapeutic results. The reduction in the incidence of dementia/AD appears promising but it should be confirmed in the future. A reevaluation of the AD concept is also necessary.

Prenatal Exposure to the 1944-45 Dutch Famine and Risk for Dementia up to Age 75: An Analysis of Primary Care Data

BACKGROUND

A poor prenatal environment adversely affects brain development. Studies investigating long-term consequences of prenatal exposure to the 1944-45 Dutch famine have shown that those exposed to famine in early gestation had poorer selective attention, smaller brain volumes, poorer brain perfusion, older appearing brains, and increased reporting of cognitive problems, all indicative of increased dementia risk.

OBJECTIVE

In the current population-based study, we investigated whether dementia incidence up to age 75 was higher among individuals who had been prenatally exposed to famine.

METHODS

We included men (n=6,714) and women (n=7,051) from the Nivel Primary Care Database who had been born in seven cities affected by the Dutch famine. We used Cox regression to compare dementia incidence among individuals exposed to famine during late (1,231), mid (1,083), or early gestation (601) with those unexposed (born before or conceived after the famine).

RESULTS

We did not observe differences in dementia incidence for those exposed to famine in mid or early gestation compared to those unexposed. Men and women exposed to famine in late gestation had significantly lower dementia rates compared to unexposed individuals (HR 0.52 (95%CI 0.30-0.89)). Sex-specific analyses showed a lower dementia rate in women exposed to famine in late gestation (HR 0.39 (95%CI 0.17-0.86)) but not in men (HR 0.68 (95%CI 0.33-1.41)).

CONCLUSION

Although prenatal exposure to the Dutch famine has previously been associated with measures of accelerated brain aging, the present population-based study did not show increased dementia incidence up to age 75 in those exposed to famine during gestation.