Secular Trends in Dementia Free Cognitive Function in Older Adults: A Systematic Review

BACKGROUND

Although numerous studies have reported a decrease in dementia risk in the last two decades, it is unclear whether dementia-free cognitive function is also changing across generations.

OBJECTIVE

The objective was to systematically evaluate the published data on generational differences in cognitive function in the older population.

METHODS

Searches were performed on PubMed, Embase, and PsychInfo for articles published in English before 20 June 2021. Included studies were from population-based samples that reported generational differences in cognition in individuals without dementia, aged ≥60 years.

RESULTS

28,101 studies were identified and 15 selected covering the period from 1971 to 2015: including studies from China, Europe, and the USA. The results show generally consistent findings of improvements or stability in dementia free cognitive function in later versus earlier born generations, but not for all cognitive domains. Prevalence of mild cognitive impairment and cognitive impairment no dementia has remained stable in the USA, UK, and China over the last two decades.

RESULTS

Prevalence of vascular related mild cognitive impairment has increased in China. Improvements in cognition may only partially be explained by increased educational attainment across generations.

CONCLUSION

This review provides evidence for generational effects in dementia-free cognitive function, predominately stability or improvements in performance, in later compared to earlier born individuals across different world regions. There is an urgent need to determine the factors driving such changes and whether they are being experienced in all world regions, particularly low- and middle-income countries where the burden of cognitive impairment is greatest and rising.

Vapor cannabis exposure generationally affects male reproductive functions in mice

This study was performed to examine whether vapor exposure to cannabis plant matter negatively impacts male reproductive functions and testis development in mice. Adult CD-1 male mice (F0) were exposed to air (control) or 200 mg of vaporized cannabis plant matter 3x/day over a 10 day period. Subsequently, F0 males were bred with drug naïve CD-1 females to generate F1 males, and F1 offspring were used to generate F2 males. Cannabis vapor exposure decreased sperm count and/or motility in F0 and F1 males and disrupted the progression of germ cell development, as morphometric analyses exhibited an abnormal distribution of the stages of spermatogenesis in F0 males. Although plasma levels of testosterone were not affected by cannabis exposure in any ages or generations of males, dysregulated steroidogenic enzymes, Cyp11a1 and Cyp19a1, were observed in F0 testis. In the neonatal testis from F1 males, while apoptosis was not altered, DNA damage and DNMT1, but not DNMT3A and DNMT3B, were increased in germ cells following cannabis exposure. In contrast, the alterations of DNA damage and DNMT1 expression were not observed in F2 neonatal males. These results suggest that cannabis vapor exposure generationally affects male reproductive functions, probably due to disruption of spermatogenesis in the developing testis.

Developmental toxicity of bisphenol S in Caenorhabditis elegans and NODEF mice

The growing concern surrounding bisphenol A (BPA) has led to increased industrial production and application of its analog bisphenol S (BPS). The goals of this study were: (1) To examine the generational effects in the nematode C. elegans for up to three generations following developmental exposure to BPS (0.1, 1.0, 5.0 and 10.0 μM), and (2) To examine the neurotoxicity and metabolic toxicity in NODEF mouse offspring exposed to BPS (3 μg/kg BW) in utero throughout gestation once/day via oral pipette. First, worms were exposed to BPS developmentally for a single period of 48 hours and then propagated for 2 additional generations. Exposure to 0.1 and 1.0 μM BPS decreased lifespan and the number of progeny with an ability to recover in subsequent generations. In contrast, worms exposed to 5.0 or 10.0 μM BPS exhibited a continuous effect in the second generation, e.g., decreased lifespan and reduced number of progeny. Only worms exposed to 10.0 μM BPS continued to have a significant long-term effect (e.g., decreased lifespan) through the third generation. In addition, worms developmentally exposed to BPS at 5.0 μM and 10.0 μM also showed decreases in body bends. In contrast, worms exposed to 0.1 μM BPS exhibited a significant increase in head thrashes. When the multigenerational effects were examined by exposing worms to BPS for 48 hours developmentally at each generation for three generations, an accumulative effect was observed in worms treated with 0.1 or 1.0 μM BPS for two generations, but not for three generations, suggesting a threshold existed. Worms exposed to either 5.0 or 10.0 μM BPS demonstrated accumulative effects through two and three generations. When the developmental effects of BPS were studied in NODEF mice, offspring exposed gestationally exhibited behavioral deficits at 12, but not at 3, weeks of age. Specifically, female offspring had decreases in working and short-term memories while male offspring showed increases in hyperactivity and anxiety-like behaviors. In summary, this study demonstrates the sex-related effects of BPS in NODEF mouse offspring exposed in utero, along with the generational effects observed in C. elegans.

Does parental farm upbringing influence the risk of asthma in offspring? A three-generation study

BACKGROUND

A farm upbringing has been associated with lower risk of asthma and methylation of asthma-related genes. As such, a farm upbringing has the potential to transfer asthma risk across generations, but this has never been investigated. We aimed to study the generational effects from a parental farm upbringing on offspring asthma.

METHODS

Our study involved three generations: 5759 participants from the European Community Respiratory Health Survey (ECRHS) study (born 1945-1971, denoted G1), their 9991 parents (G0) and their 8260 offspring (G2) participating in RHINESSA (Respiratory Health In Northern Europe, Spain and Australia). Questionnaire data were collected on G0 and G1 from G1 in 2010 and on G2 from themselves in 2013. The parental/grandparental place of upbringing was categorized: (i) both parents from farm; (ii) mother from farm, father from village/city; (iii) father from farm, mother from village/city; (iv) both parents from village or one parent from village and one from city; (v) both parents from city (reference group). Grandparental upbringing was equivalently categorized. Offspring asthma was self-reported and data were analysed using Cox-regression models with G2 age as the time scale.

RESULTS

A parental farm upbringing was not associated with offspring asthma when compared with city upbringing [hazard ratio (HR) 1.12, 95% confidence interval (CI) 0.74-1.69]. Findings remained similar when stratified by offspring upbringing and asthma phenotypes. Quantitative bias analyses showed similar estimates for alternative data sources. A grandparental farm upbringing was not associated with offspring asthma in either the maternal (HR 1.05, 95% CI 0.67-1.65) or paternal line (HR 1.02, 95% CI 0.62-1.68).

CONCLUSIONS

This multigenerational analysis suggests no evidence of an association between parental/grandparental farm upbringing and offspring asthma.

Evolved changes in breathing and CO2 sensitivity in deer mice native to high altitudes

We examined the control of breathing by O₂ and CO₂ in deer mice native to high altitude to help uncover the physiological specializations used to cope with hypoxia in high-altitude environments. Highland deer mice ( Peromyscus maniculatus) and lowland white-footed mice ( P. leucopus) were bred in captivity at sea level. The first and second generation progeny of each population was raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa O₂, simulating hypoxia at ~4,300 m) for 6-8 wk. Ventilatory responses to poikilocapnic hypoxia (stepwise reductions in inspired O₂) and hypercapnia (stepwise increases in inspired CO₂) were then compared between groups. Both generations of lowlanders appeared to exhibit ventilatory acclimatization to hypoxia (VAH), in which hypoxia acclimation enhanced the hypoxic ventilatory response and/or made the breathing pattern more effective (higher tidal volumes and lower breathing frequencies at a given total ventilation). In contrast, hypoxia acclimation had no effect on breathing in either generation of highlanders, and breathing was generally similar to hypoxia-acclimated lowlanders. Therefore, attenuation of VAH may be an evolved feature of highlanders that persists for multiple generations in captivity. Hypoxia acclimation increased CO₂ sensitivity of breathing, but in this case, the effect of hypoxia acclimation was similar in highlanders and lowlanders. Our results suggest that highland deer mice have evolved high rates of alveolar ventilation that are unaltered by exposure to chronic hypoxia, but they have preserved ventilatory sensitivity to CO₂.

Regional Disparities in Adult Height, Educational Attainment and Gender Difference in Late- Life Cognition: Findings from the Longitudinal Aging Study in India (LASI)

State policies over time in India may have led to significant differences by sex in population health and cognition. In this paper, we use data from the pilot wave of the Longitudinal Aging Study in India, conducted in Karnataka, Kerala, Punjab, and Rajasthan, to examine state variations in health, educational attainment, and male preference, and how these variations contribute to gender differences in late-life cognition in India. We find men and women born in Punjab are taller than those elsewhere, but do not find any gender differences in height across states with differential male preference. We do find a significant gap in educational attainment that correlates with male preference. We find paternal education benefits both sons and daughters, while maternal education contributes to daughters' educational attainment. Finally, we find that paternal education benefits daughters' late-life cognition, while maternal education benefits sons' late-life cognition, and that children's education has positive association with older adults' cognitive functioning as well.