Secular Decreases Research Articles

Temporal Trends in the Prevalence of Dementia in South Korea

Background. Secular decreases in the prevalence of cognitive impairment and dementia have been observed in several Western countries, however, few systematic investigations of temporal trends in dementia have been conducted in South Korea. Method. Data came from N=8,006 individuals (N=2,110 assessed twice) aged 65 years and older participating in the Korean Longitudinal Study of Aging 2008 and 2018. Dementia was indicated by a score ≤ 17 on the Korean Mini-Mental State Examination (K-MMSE). Dementia was regressed on the year of survey, adjusting for multiple demographic and socio-economic confounders, and, in additional models, also chronic diseases and lifestyle factors related to health, social, and religious activities. Results. Across waves, the share of individuals with low socio-economic status decreased. The prevalence of chronic diseases, including diabetes, heart diseases, stroke, and psychiatric diseases, increased over time. Alcohol consumption increased, whereas smoking rates, religious affiliation, and participation in religious activities decreased. Controlling for all covariates and compared to 2008, we observe decreases in dementia prevalence in 2018 by 52% (2018: OR 0.48, CI 0.42, 0.56). Women’s MMSE scores were more than two times as likely as men’s to indicate dementia (OR 2.59, CI 2.15, 3.14). Discussion. Decreases in dementia prevalence in Korea are partly attributable to improved socio-economic conditions and can be observed despite the increased prevalence of chronic conditions. However, secular trends were not fully explained by these and lifestyle factors. We discuss further individual-level and contextual-level mechanisms that may have contributed to these findings.

A speckle-imaging search for close triple companions of cataclysmic binaries

ABSTRACT The orbital periods of most eclipsing cataclysmic binaries are not undergoing linear secular decreases of order a few parts per billion as expected from simple theory. Instead, they show several parts per million increases and decreases on time-scales of years to decades, ascribed to magnetic effects in their donors, triple companions, or both. To directly test the triple companion hypothesis, we carried out a speckle-imaging survey of six of the nearest and brightest cataclysmic variables. We found no main-sequence companions earlier than spectral types M4V in the separation range ∼0.02–1.2 arcsec, corresponding to projected linear separations of ∼2–100 au, and periods of ∼3–1000 yr. We conclude that main-sequence triple companions to cataclysmic variables are not very common, but cannot rule out the presence of the faintest M dwarfs or close brown dwarf companions.

A Summary of the 2020 Gastric Cancer Summit at Stanford University

There exists no coherent national strategy for the early detection or prevention of gastric cancer in the United States (US), even among identified high-risk groups such as Asian Americans, African Americans, Hispanic Americans, and Alaska Native/American Indian peoples. As a result, patients with gastric cancer in the US are diagnosed at later stages and demonstrate worse overall survival compared to nations of East Asia with established screening programs (Table 1). The under-recognition of gastric cancer risk within minority communities is a significant unaddressed healthcare disparity.

Prevalence of high blood pressure and high normal blood pressure among 7- to 17-year-old children and adolescents in developed regions, China from 2014 to 2017: using new national blood pressure reference for Chinese children and adolescents.

As the first blood pressure (BP) reference considering influence of height in China, national blood pressure reference for Chinese han children and adolescents aged 7 to 17 years (CCBP) was issued in 2017. The current study aimed to observe the short-term trends in BP and prevalence of high blood pressure (HBP) and high normal blood pressure (HNBP) using this CCBP reference in Suzhou, China. Data of children and adolescents aged 7 to 17 years were collected from 2014 to 2017. Total population of 2014 to 2017 were 617,383, 684,453, 695,302, and 774,605, respectively, and proportions of males were 54.1%, 54.0%, 53.9%, and 53.8%, respectively. P-trend tests were conducted to examine the trends of BP among different age, region, body mass index, and socioeconomic status groups for each gender. Multivariate logistic regression analyses found secular decreases in prevalence of HBP and HNBP, after adjustment for potential confounders. Compared with that in 2014, the odds ratios (95% confidence intervals) for total study population were 0.936 (0.928, 0.944) in 2015, 0.879 (0.872, 0.887) in 2016, and 0.934 (0.926, 0.941) in 2017. In conclusion, prevalence of HBP and HNBP decreased among children and adolescents in developed regions of China from 2014 to 2017, and a slight rise were found in 2017.

Rarity and persistence.

Rarity is a population characteristic that is usually associated with a high risk of extinction. We argue here, however, that chronically rare species (those with low population densities over many generations across their entire ranges) may have individual-level traits that make populations more resistant to extinction. The major obstacle to persistence at low density is successful fertilisation (union between egg and sperm), and chronically rare species are more likely to survive when (1) fertilisation occurs inside or close to an adult, (2) mate choice involves long-distance signals, (3) adults or their surrogate gamete dispersers are highly mobile, or (4) the two sexes are combined in a single individual. In contrast, external fertilisation and wind- or water-driven passive dispersal of gametes, or sluggish or sedentary adult life habits in the absence of gamete vectors, appear to be incompatible with sustained rarity. We suggest that the documented increase in frequency of these traits among marine genera over geological time could explain observed secular decreases in rates of background extinction. Unanswered questions remain about how common chronic rarity actually is, which traits are consistently associated with chronic rarity, and how chronically rare species are distributed among taxa, and among the world's ecosystems and regions.

Orbital period variations of the eclipsing binaries TU Cnc, VZ Leo, and OS Ori

Variations of the orbital periods of the eclipsing binaries TU Cnc, VZ Leo, and OS Ori are analyzed. Secular period decreases were earlier believed to occur in these systems. It is demonstrated that the period variations of TU Cnc can be represented using the light-time effect corresponding to the orbital motion of the eclipsing binary with a period of 78.6 years around the center ofmass of the triple system, with the mass of the third body being M 3 > 0.82M ⊙. With the same accuracy, the period variations of VZ Leo and OS Ori can be represented either solely using the light-time effect, or a superposition of a secular period decrease and the light-time effect. For VZ Leo, the period of the long-term orbit is 63.8 years in the former case and 67.9 years in the latter case. Similar masses for the third body are indicated in both cases: M 3 > 0.55M ⊙ and M 3 > 0.61M ⊙. For OS Ori, the period of the long-term orbit is 46 years and M 3 > 0.5M ⊙ in the former case, and the period is 36 years and M 3 > 0.6M ⊙ in the latter case.

Biogeochemical modelling of dissolved oxygen in a changing ocean.

Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'.

Progress in low-frequency radio astronomy and I.S. Shklovskii’s contribution to its development

Radio astronomy at decameter wavelengths is currently undergoing very active development. Large-scale, new generation low-frequency radio telescopes are being constructed and already used in many countries around the world. As before, the largest, most sensitive, and most versatile telescope at decameter wavelengths is the Ukrainian UTR-2 radio telescope operating at 8–32 MHz, which has an effective area of more than 105 m2 and an angular resolution of about 0.5◦, as well as the URAN interferometric system based on the UTF-2. Many studies that have been carried out on these facilities have been based on important results and far-sighted predictions of Shklovskii. These include, in particular, studies of dynamical spectra and the brightness distributions of the sporadic and quiescent decameter radio emission of the hot solar corona, complex, broadband radio spectroscopy of the interstellar medium, and multi-frequency monitoring of secular decreases in the flux densities of supernova remnants. The coordinated use of highly effective existing and newly constructed radio telescopes joined into ground networks, as well as specialized space missions, are opening new prospects for low-frequency radio astronomy.

Trends in Incidence of Hospitalized Acute Myocardial Infarction in the Cardiovascular Research Network (CVRN)

BackgroundMonitoring trends in cardiovascular events can provide key insights into the effectiveness of prevention efforts. Leveraging data from electronic health records provides a unique opportunity to examine contemporary, community-based trends in acute myocardial infarction hospitalizations. MethodsWe examined trends in hospitalized acute myocardial infarction incidence among adults aged ≥25 years in 13 US health plans in the Cardiovascular Research Network. The first hospitalization per member for acute myocardial infarction overall and for ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction was identified by International Classification of Diseases, Ninth Revision, Clinical Modification primary discharge codes in each calendar year from 2000 through 2008. Age- and sex-adjusted incidence was calculated per 100,000 person-years using direct adjustment with 2000 US census data. ResultsBetween 2000 and 2008, we identified 125,435 acute myocardial infarction hospitalizations. Age- and sex-adjusted incidence rates (per 100,000 person-years) of acute myocardial infarction decreased an average 3.8%/y from 230.5 in 2000 to 168.6 in 2008. Incidence of ST-segment elevation myocardial infarction decreased 8.7%/y from 104.3 in 2000 to 51.7 in 2008, whereas incidence of non-ST-segment elevation myocardial infarction increased from 126.1 to 129.4 between 2000 and 2004 and then decreased thereafter to 116.8 in 2008. Age- and sex-specific incidence rates generally reflected similar patterns, with relatively larger decreases in ST-segment elevation myocardial infarction rates in women compared with men. As compared with 2000, the age-adjusted incidence of ST-segment elevation myocardial infarction in 2008 was 48% lower among men and 61% lower among women. Conclusions and RelevanceAmong a large, diverse, multicenter community-based insured population, there were significant decreases in incidence of hospitalized acute myocardial infarction and the more serious ST-segment elevation myocardial infarctions between 2000 and 2008. Decreases in ST-segment elevation myocardial infarctions were most pronounced among women. While ecologic in nature, these secular decreases likely reflect, at least in part, results of improvement in primary prevention efforts.

FAMILIES OF PLAUSIBLE SOLUTIONS TO THE PUZZLE OF BOYAJIAN’S STAR

ABSTRACT Good explanations for the unusual light curve of Boyajian's Star have been hard to find. Recent results by Montet & Simon lend strength and plausibility to the conclusion of Schaefer that in addition to short-term dimmings, the star also experiences large, secular decreases in brightness on decadal timescales. This, combined with a lack of long-wavelength excess in the star's spectral energy distribution, strongly constrains scenarios involving circumstellar material, including hypotheses invoking a spherical cloud of artifacts. We show that the timings of the deepest dimmings appear consistent with being randomly distributed, and that the star's reddening and narrow sodium absorption is consistent with the total, long-term dimming observed. Following Montet & Simon's encouragement to generate alternative hypotheses, we attempt to circumscribe the space of possible explanations with a range of plausibilities, including: a cloud in the outer solar system, structure in the interstellar medium (ISM), natural and artificial material orbiting Boyajian's Star, an intervening object with a large disk, and variations in Boyajian's Star itself. We find the ISM and intervening disk models more plausible than the other natural models.

RY AQUARIUS A BINARY SYSTEM WITH PULSATING δ-SCUTI PRIMARY COMPONENT

ABSTRACT We present simultaneous new BVI light curves along with radial velocity curve analysis of the RY Aqr system, using the PHysics Of Eclipsing BinariEs code. The analysis indicates that while the primary is completely inside its Roche critical surface, the secondary has filled out its Roche surface. In addition, the positions of the system components on M–R, H–R diagrams are specified, which show that the primary is a main-sequence or nearly main-sequence star while the secondary is an evolved subgiant. In addition, analysis of the period and luminosity variations of the system were carried out. Fourier frequency analysis of light variation indicates that the primary is a pulsating, δ-scuti variable star. Moreover, O–C curve analysis shows that the period of the system is secularly decreasing with a rate of dp/dt = 0.074 s yr−1. This decrease in the orbital period variations was attributed to a mass and angular momentum loss from the system with a rate of Apart from the secular period decreases, the orbital period of the system is modulated by a cyclic period of 72.69 year, which was attributed to a third body orbiting around the barycenter of the system.

The Substitution Elasticity, Factor Shares, Long-Run Growth, and the Low-Frequency Panel Model

The value of the elasticity of substitution between labor and capital (o) is a “crucial” assumption in understanding the secular decline in the labor share of income and long-run growth. This paper develops and implements a new strategy for estimating this crucial parameter by combining a low-pass filter with panel data to identify the low-frequency/long-run relations appropriate to production function estimation. Using spectral analysis, we assess the extent to which our choices of the critical periodicity and window defining the low-pass filter are successful in emphasizing long-run variation. The empirical results are based on the comprehensive panel industry dataset constructed by Dale Jorgenson and his research associates. Our preferred estimate of o is 0.40. We document that standard estimation methods, which do not filter-out transitory variation, generate downwardly biased estimates. As high frequency variation is introduced into the model variables, o declines by 40% to 70% relative to the benchmark value. Despite correcting for this bias, our preferred estimate is substantially below the Cobb-Douglas assumption of o = 1, and thus implies that the secular decline in the labor share of income cannot be explained by secular increases in the capital/income ratio or secular decreases in the relative price of investment or capital taxation.

Exploring the determinants of secular decreases in dental caries among Korean children

The aim of this study was to determine the contributions of sealant and water fluoridation to the time trends in dental caries from 2003 to 2010. Data were from three waves of the Korean National Oral Health Surveys between 2003 and 2010, including a total of 23 059 children (11 889 boys and 11 170 girls) aged 8, 10, and 12 years. The impacts of sealant and water fluoridation on dental caries were obtained by logistic regression for each age group of children. The contributions of sealant and water fluoridation to the time trends in the prevalence of dental caries were examined by a series of logistic regression models, and changes in the adjusted odds ratios for each survey year were also calculated. Over the past 7 years, the prevalence of dental caries decreased dramatically. Although sealant had a significant impact on dental caries in each survey year, remarkable decreases in dental caries from 2003 to 2010 were not explained by the secular changes in the dental sealant or water fluoridation factor. We observed important population declines in dental caries in Korea in children aged 8-12 years; however, the likely causes for these secular trends remain to be determined.

Explaining the Decline in Coronary Heart Disease Mortality in Portugal Between 1995 and 2008

We aimed to quantify the contribution of treatments and risk factors to the decline in coronary heart disease (CHD) mortality in Portugal, 1995 to 2008. The IMPACT mortality model was used to integrate data on trends in uptake of treatments and exposure to risk factors to explain the CHD mortality variation. Between 1995 and 2008, CHD mortality rates in Portugal decreased by 29% in men and 21% in women aged 25 to 84 years, corresponding to 3760 fewer deaths in 2008 than expected if 1995 mortality rates had persisted. Approximately 92% of the estimated decrease in number of deaths could be explained by the model; the remaining 8% were attributed to changes in unmeasured factors. Approximately 50% of the decrease explained by the model was attributable to an increased uptake of treatments, mainly antihypertensive medication (12%) and initial treatments after an acute myocardial infarction (10%), and 42% to population risk factor reductions, mainly blood pressure (27% in men and 60% in women), total cholesterol (14% in men and 5% in women), and smoking (11% in men). However, these reductions were partially offset by adverse trends in diabetes mellitus (18% in men and 2% in women) and obesity (6% in men and 5% in women) and smoking (2% in women). In this low CHD risk population, modern treatments explained approximately half of the overall decline in CHD deaths. The biggest contributions to the CHD mortality decline came from secular decreases in blood pressure and increases in hypertension treatment.

Exploring Determinants of Secular Decreases in Childhood Blood Pressure and Hypertension

Childhood blood pressure is largely uninfluenced by medical treatment and behavioral changes associated with hypertension diagnosis. Examining secular trends in childhood blood pressure and its contributing factors will help us better understand population-level determinants of blood pressure and hypertension. Data were from 4 waves of the Korean National Health and Nutrition Examination Survey between 1998 and 2008, including a total of 5909 boys and girls 10 to 19 years of age. Over the past 10 years, age- and height-adjusted mean systolic blood pressure decreased substantially from 115.6 to 106.9 mm Hg (by 8.7 mm Hg) among boys and from 111.8 to 101.8 mm Hg (by 10.0 mm Hg) among girls. Associated childhood hypertension and prehypertension/hypertension prevalences decreased by 52% to 86%. These remarkable decreases were found among all age and socioeconomic groups and were not explained by secular changes in childhood obesity (body mass index and waist circumferences), health behaviors (cigarette smoking and physical activity), nutritional factors (sodium, potassium, total energy, protein, and fat intake), psychological factors (perceived stress and sleep duration), and sociodemographic factors (annual household income and family size). We observed important population declines in blood pressure in Korea over a 10-year period in children 10 to 19 years of age, but the likely causes for these secular trends remain to be determined.

Recent trends in trading activity and market quality

We explore the sharp uptrend in recent trading activity and accompanying changes in market efficiency. Higher turnover has been associated with more frequent smaller trades, which have progressively formed a larger fraction of trading volume over time. Evidence indicates that secular decreases in trading costs have influenced the turnover trend. Turnover has increased the most for stocks with the greatest level of institutional holdings, suggesting professional investing as a key contributor to the turnover trend. Variance ratio tests suggest that more institutional trading has increased information-based trading. Intraday volatility has decreased and prices conform more closely to random walk in recent years. The sensitivity of turnover to past returns has increased and cross-sectional predictability of returns has decreased significantly, revealing a more widespread use of quantitative trading strategies that allow for more efficient securities prices.

Secular decreases in fracture rates 1986–2006 for Manitoba, Canada: a population-based analysis

We examined trends in fracture rates over 20 years in the Province of Manitoba, Canada. Hip fractures, major low-trauma fractures, and high-trauma fractures declined significantly from 1986 to 2006. Secular decreases in hip fracture rates have been reported in some countries. Whether this phenomenon applies to other fracture sites is not well described. We used 20 years of data from the Population Health Research Data Repository for the Province of Manitoba, Canada. Age-adjusted fracture rates were calculated for men and women age 50 years and older 1986-2006 according to fracture site and mechanism (presence/absence of external injury codes). Generalized linear models with generalized estimating equations were used to derive adjusted annual rates and test for linear change in men and women. Major low-trauma fractures (hip, forearm, spine, and humerus) showed a significant annual linear decline in women (-1.2% [95% CI, -0.7% to -1.8%]) and in men (-0.4% [95% CI, -0.7% to -0.2%]). Hip fracture showed a significant annual decline for both sexes, while forearm and humerus fractures showed a significant decline only in women. The only fracture category that did not show a significant annual decline in either sex was the spine. The observed annual reduction in high-trauma fractures was even larger and did not show a sex difference (-1.8% [95% CI, -2.8% to -0.7%]). We observed a decrease in both low-trauma and high-trauma fracture rates over the study period. This decline was apparent in years prior to widespread osteoporosis testing or availability of modern pharmacotherapy.

Recent Trends in Trading Activity and Market Quality

We explore the sharp uptrend in recent trading activity and accompanying changes in market efficiency. Higher turnover has been associated with more frequent smaller trades, which have progressively formed a larger fraction of trading volume over time. Evidence indicates that secular decreases in trading costs have influenced the turnover trend. Turnover has increased the most for stocks with the greatest level of institutional holdings, suggesting professional investing as a key contributor to the turnover trend. Variance ratio tests suggest that more institutional trading has increased information-based trading. Intraday volatility has decreased and prices conform more closely to random walk in recent years. The sensitivity of turnover to past returns has increased and cross-sectional predictability of returns has decreased significantly, revealing a more widespread use of quantitative trading strategies that allow for more efficient securities prices.

Did natural reactors form as a consequence of the emergence of oxygenic photosynthesis during the Archean?

The advent of oxygenic photosynthesis changed Earth’s surface environment in numerous ways, perhaps most notably by making possible the evolution of large and complex life-forms. Current models suggest that organisms that can perform oxygenic photosynthesis first took hold in isolated marine and freshwater basins, producing local oxygen oases. Here we present calculations that suggest that uranium deposits could have formed at the margins of these basins due to the strong local reductionoxidation gradients. Because of the high abundance of 235 U at this time, these uranium deposits could have formed widespread, near-surface, critical natural fission reactors. These natural reactors would have represented point sources of heat, ionizing radiation, and free radicals. Additionally, they would have far-field effects through the production of mobile short- and long-lived radioactive daughter isotopes and toxic byproducts. It is possible that these fission products pro vided a negative feedback, helping to limit the proliferation of the cyanobacteria in the Archean environment. Secular decreases in the abundance of 235 U in

Recent Trends in Trading Activity

We explore the sharp uptrend in trading activity during recent years. Higher turnover has been associated with more frequent smaller trades, which have progressively formed a larger fraction of trading volume over time. Evidence indicates that secular decreases in trading costs have influenced the turnover trend. Turnover has increased the most for stocks with the greatest level of institutional holdings, suggesting professional investing as a key contributor to the turnover trend. Variance ratio tests suggest that more institutional trading has increased information-based trading. The sensitivity of turnover to past returns has increased significantly, revealing a more widespread use of quantitative trading strategies.