Age Structure Of Population Research Articles

Persistence and change in regional entrepreneurship performance: a three-economy comparison

ABSTRACT This paper compares the factors related to the persistence and change of regional levels of new business formation in the United States, England and Wales, and West Germany. The three economies are highly comparable both in levels of path dependency in their regional start-up rate rankings and in the factors related to long-term changes in regional start-up performance. Regional levels of human capital, foreign-born population and population density explain improvement regional performance, whereas regional wages, population age structure, small firm presence and regional industry structure are not major factors. We propose policy implications and an agenda for further research.

Comparison of Epidemiological data from Switzerland and Germany – Part 1

AbstractThe epidemiological and health statistical comparison of the populations of Germany and Switzerland on the basis of various parameters shows a very similar population structure. This can be seen primarily in the age and gender structure of both populations, which are almost identically distributed. This generally enhances the informative value of the parameters compared. Challenges in the comparison of the data were primarily identified as different survey dates, a different population under consideration, and, for individual disease patterns, the collection of different parameters within the two countries. Since some sources were surveys, a bias of the results due to the subjective assessment of the participants cannot be excluded.

Impacts of ground-based ULV pyrethroid sprays on abundance and age structure of the Zika vector, Aedes aegypti (Diptera: Culicidae), in urban Arizona.

Aedes aegypti (L.), the primary mosquito vector of arboviruses such as dengue and Zika, has a global distribution that includes the southern United States. Control of this peridomestic mosquito is challenging. Ultra-low volume (ULV) pyrethroid sprays are commonly used against adult mosquitoes to break transmission during a disease outbreak, although efficacy data are limited. This study examined the impacts of ULV sprays on Ae. aegypti vectorial capacity as measured by vector abundance and age structure in two cities in Maricopa County, AZ with robust Ae. aegypti populations and a well-developed vector management program. We assessed impacts of routine ULV applications conducted by Maricopa Vector Control Division during the summer rainy seasons of 2017 to 2019 to determine whether existing practices mainly targeting Culex spp. also suppressed Ae. aegypti. The insecticide formulations applied for Culex spp. control (Duet and Permanone 30-30) did not affect Ae. aegypti abundance, but Duet applications slightly reduced female mosquito age. Deltagard, the insecticide product used specifically against Ae. aegypti, was only applied three times in 2018 over small areas, so efficacy assessment was difficult. Deltagard was associated with a small decline in Ae. aegypti abundance. CDC bottle bioassays of Ae. aegypti collected in the study area showed resistance to permethrin and deltamethrin. Overall, the lack of significant mosquito population suppression or age structure changes after insecticide applications suggest that current tools used by Maricopa Vector Control Division are unlikely to effectively control Ae. aegypti populations in the event of a disease outbreak.

The dynamics of hunting mammal species populations in Yakutia during the 20th century

Anthropogenic influences have emerged as significant ecological drivers affecting the survival of various animalspecies in the 20th century. Numerous researchers have demonstrated that climate warming and anthropogenic disturbances – including the degradation of ecological barriers – have facilitated the northward expansion of new avian and mammalian species. Concurrently, these anthropogenic pressures exert several detrimental effects. We conducted a comprehensive study on the population trends of some game mammal species in Yakutia. Data collection has been ongoing since 1962 and employs standardized ecological methodologies, including transect surveys, short-term observational protocols, and stationary work, which are typically conducted simultaneously at three to four sites. Ecological monitoring encompassed all seasonal cycles. Aerial censuses of moose, tundra populations of wild reindeer, and brown bears were conducted throughout the entire territory of Yakutia. Furthermore, structured interviews with commercial hunters and analyses of hunting statistics spanning from 1935 to 1985 were undertaken. Throughout the 20th century, fluctuations in population abundance and demographic dynamics were observed among key game mammal species, including the mountain hare, Eurasian red squirrel, wolf, brown bear, moose, and wild reindeer. The population density of the river otter remains critically low, while the red fox, Eurasian lynx, and wolverine maintain low but stable populations, with no discernible contraction in their distribution ranges. A disturbance in the sex and age structure of the wild reindeer population has been identified. The primary factor regulating the population dynamics of the mountain hare, large carnivores, and ungulates has been determined to be hunting pressure. The underlying causes of the population decline of the Eurasian red squirrel remain unresolved. This research has facilitated the refinement of species distribution maps, including the northernmost range limits of the brown bear. The absence of rigorous conservation measures presents a significant threat to certain mammalian taxa, such as the Sundrun population of wild reindeer.

Global, regional, and national burden of refraction disorders: findings from the global burden of disease study 2021 and projections to 2050

BackgroundRefraction disorders are the leading cause of visual impairment worldwide. This study investigates the global burden and trends of refraction disorders from 1990 to 2021, with projections extending to 2050.MethodsData on prevalence and disability-adjusted life years (DALYs) for refraction disorders, along with their 95% uncertainty intervals (UIs), were obtained from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021. The study provides a comprehensive analysis of the epidemiology of refraction disorders at global, regional, and national levels. It examines trends from 1990 to 2021 from multiple dimensions, including overall and localized changes. Burden decomposition was performed to assess contributions from population size, age structure, and epidemiological changes. Cross-country inequalities were quantified using standard health equity methods recommended by the World Health Organization. Future changes in the burden of refraction disorders were also projected through 2050.ResultsAccording to GBD 2021 estimates, there were 159,765,917 prevalent cases (95% UI: 142,526,915–178,698,348) and 6,618,600 DALYs (95% UI: 4,599,082–9,528,676) due to refraction disorders globally in 2021. From 1990 to 2021, prevalence and DALYs rates demonstrated a steady decline, although prevalence numbers, incidence numbers, and rates were consistently higher among females compared to males. Decomposition analysis showed that aging, population growth, and epidemiological changes contributed 36.25%, 76.92%, and − 13.18%, respectively, to changes in the age-standardized prevalence rate (ASR). The concentration index declined from − 0.17 (95% CI: −0.21 to − 0.13) in 1990 to − 0.10 (95% CI: −0.13 to − 0.07) in 2021, indicating a reduction in SDI-related inequalities. By 2050, the ASR for prevalence and DALYs is projected to decline to 1815.27 (95% UI: 534.15–3096.40) and 69.11 (95% UI: 21.45–116.77), respectively.ConclusionThe global burden of refraction disorders decreased significantly from 1990 to 2021 and is expected to decline further by 2050. Females continue to experience a greater burden compared to males. Population growth emerged as the primary driver of changes in the ASR of prevalence and DALYs. While countries with low socio-demographic index (SDI) face a disproportionately high burden, SDI-related inequalities have gradually lessened over time.

Rethinking the evidence on COVID-19 in Africa.

Rethinking the evidence on COVID-19 in Africa.

Community Characteristics and Population Dynamics of an Endangered Rhododendron nymphaeoides.

Rhododendron nymphaeoides belongs to the Fortunea subsection of the Rhododendron genus. Despite being officially listed as an endangered species (with the conservation status of EN) by the International Union for Conservation of Nature Red List, The Red List of Rhododendrons, Red List of China's Higher Plants, and the Threatened Species List of China's Higher Plants, little is known about this species' community characteristics and population dynamics. This lack of knowledge hampers the conservation and management of its wild resources. This study was conducted on all existing distribution points of R. nymphaeoides through field investigations, revealing the species composition and community structure of its populations. This included analyzing the diameter class structure, creating life tables and survival curves, and analyzing population dynamics indices to shed light on the dynamics of the R. nymphaeoides populations. The results showed: (1) the four communities collectively comprise 122 species of vascular plants belonging to 55 families and 79 genera, with tropical elements predominantly influencing the community structure and environmental formation. Community IV exhibited the highest species diversity, Community III had the most even distribution of species, and Community II had the lowest species diversity. (2) A total of 288 R. nymphaeoides individuals were recorded, showing a spatially clustered distribution. (3) The age structure of the HSC population exhibits a reverse J-shape, indicating a growing population, but there are still constraints in the transition from seedlings to saplings; the LSK population has a substantial number of young individuals and the highest proportion of middle-aged individuals, characterizing it as a stable population; whereas the LZH and HTS populations have few young individuals and a high proportion of middle-aged individuals, with an age structure that is spindle-shaped and trending toward aging, placing these populations at significant risk of decline. (4) The survival curves for all four populations were of the Deevey-II type, characterized by high mortality rates among seedlings. (5) The primary reasons for the difficulty in population renewal and development are the extremely low natural germination rates of seeds, weak competitiveness of seedlings, growth restricted to limestone mountain areas above 1500 m with thin soil layers, and frequent human disturbances. Therefore, conservation strategies that integrate insitu conservation, ex situ conservation, and reintroduction are recommended. Emphasis should be placed on long-term monitoring of R. nymphaeoides populations and communities, enhanced management during the sapling stage, and efforts in seedling propagation and population restoration to achieve population strengthening and the natural reintroduction of artificially cultivated populations, thereby maintaining the population in a healthy state.

Modelling the effect of vaccination on the dynamics of tuberculosis in an age-structured population

Despite several efforts, Tuberculosis (TB) is still a global leading cause of death. This paper proposed an age-structured deterministic model governing the transmission dynamics and control of TB in the presence of vaccination integrated into the eligible population. Qualitative analysis of the model was carried out to obtain the disease-free equilibrium point of it. The effective reproduction number, Re , of the model was calculated using the next generation matrix method, which offered a numerical indicator of the potential for TB transmission in the age-structured population. Numerical analysis further offers some insightful information about how the key sensitive parameters and the vaccination rate influence the transmission dynamics and control of TB in an age-structured populationsettings.

Sex disparity in non-communicable disease burden in Iran from 1990 to 2021 based on the global burden of disease study

Non-communicable diseases (NCDs) pose a major health challenge worldwide, especially in low- and middle-income countries like Iran. Understanding sex disparities in NCDs is crucial for tailoring public health strategies to address unique risks and outcomes for different sexes. This study focused on 11 major NCD categories, estimating incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life years (DALYs). Age-standardized rates were calculated, values were presented with 95% uncertainty intervals (95% UI). Decomposition analysis assessed the impact of population growth, age structure, and incidence rates on incidence and death rates. In 2021, Iran had 80.2 million prevalent NCD cases, with slightly higher age-standardized prevalence in females. The age-standardized incidence rate was higher in females across all age groups, reaching 181,264.4 (95% UI: 165,696.5 to 200,091.3) in females and 131,900.5 (95% UI: 120,657.2 to 145,496.4) in males. Although the age-standardized death rate decreased more in males, it remained higher in males (477.6 (456.7 to 497.2)) than females (438.1 (420.3 to 455.5)). DALYs were moderately higher in females (19,983.4 (16,884.3 to 23,410.1)). In all provinces, YLLs were higher than YLDs for females, while the reverse was true for males in most provinces. These findings underscore the need for targeted public health interventions to address NCDs in females and males. While in males deaths are higher, in females DALYs are slightly higher which calls for tailored intervention to prevent death and disability.

Global, regional, and national burden of myelodysplastic syndromes and myeloproliferative neoplasms, 1990-2021: an analysis from the global burden of disease study 2021.

To analyze the trends and cross-country inequalities in the burden of Myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) over the past 30 years and forecast potential changes through 2045. Estimates and 95% uncertainty intervals (UIs) for incidence, deaths, and disability-adjusted life-years (DALYs) associated with MDS/MPN were obtained from the Global Burden of Diseases (GBD) 2021 database. We described the epidemiology of MDS/MPN at global, regional, and national levels, analyzed trends in the burden of MDS/MPN from 1990 to 2021 through overall, local, and multidimensional perspectives, decomposed the burden based on population size, age structure, and epidemiological changes, quantified cross-country inequalities in MDS/MPN burden using standard health equity methods recommended by the WHO, and predicted changes of MDS/MPN burden to 2045. The global incidence of MDS/MPN has shown a marked increase, escalating from 171,132 cases in 1990 to 341,017 cases in 2021. Additionally, the burden was found to be significantly greater in men compared to women. The overall global burden of MDS/MPN exhibited a consistent increase from 1990 to 2021, although the growth rate showed a noticeable slowdown between 2018 and 2021. Decomposition analysis identified population growth as a key factor influencing the variations in the burden of MDS/MPN. An inequality analysis across countries indicated that high Socio-demographic Index (SDI) countries bore a disproportionate share of the MDS/MPN burden, with significant SDI-related disparities remaining evident. Interestingly, while the incidence and deaths of MDS/MPN, along with the age-standardized rate (ASR) for DALYs, are projected to decline annually from 2020 to 2045, the absolute number of cases for these indicators is expected to continue rising. By 2045, the projected numbers are estimated to reach 457,320 cases for incidence, 82,047 cases for deaths, and 1,689,518 cases for DALYs. As a major public health issue, the global burden of MDS/MPN showed an overall increasing trend from 1990 to 2021, which was primarily driven by population growth and aging. The largest share of the MDS/MPN burden was seen primarily in men, with older demographics. Countries with elevated SDI experienced a significantly higher burden of MDS/MPN. While the burden of MDS/MPN was most pronounced in high SDI quintile, the fastest growth was observed in the low-middle SDI quintile, especially in tropical Latin America. This study highlighted great challenges in the control and management of MDS/MPN, including both growing case number and distributive inequalities worldwide. These findings provide valuable insights for developing more effective public health policies and optimizing the allocation of medical resources.

Epidemic evolutionarily stable strategies within an age-structured host population

To understand infectious disease dynamics, we need to understand the inextricably intertwined nature of the ecology and evolution of pathogens and hosts. Epidemiological dynamics of many infectious diseases have highlighted the importance of considering the demographics of the societies in which they spread, particularly with respect to age structure. In addition, the waves of the recent COVID-19 pandemic driven by variant replacements at an unprecedented speed show that it is vital to consider the evolutionary aspects. The classic trade-off theory of virulence addresses aspects of pathogen evolution, but here we explore in more detail the possibility of society-specific evolutionarily stable strategies (ESS) during an unfolding pandemic. Theory posits the existence under some conditions of an ESS representing the evolutionary endpoint of change. By using a demographically realistic model incorporating infection rates that vary with age, we outline which evolutionary scenarios are plausible. Focusing on the rate of infection and duration of infectivity, we ask whether an ESS exists, what characterizes it, and as a result which long-term public-health consequences may be expected. We demonstrate that the ESS of an evolving pathogen depends upon the background age-dependent frailty and mortality rates. Our findings shed important light on the plausible long-term trajectories of highly evolvable novel pathogens.

Growth Bound and Strong Ergodicity for an Almost Periodic and Age-Structured Population Model

Growth Bound and Strong Ergodicity for an Almost Periodic and Age-Structured Population Model

Drivers of primary care appointment volumes before and after the COVID-19 pandemic: a longitudinal study

BackgroundThe COVID-19 pandemic led to significant reconfiguration of primary care systems internationally. For example, a large proportion of face-to-face appointments have been replaced by telephone or online consultations. As a result, the relationship between primary care appointment provision and some of its key determinants, such as workforce and demographic characteristics, are likely to have changed. Conclusions from previous studies which used only pre-pandemic data may no longer be applicable under these new configurations.MethodsThis study aims to investigate whether the relationships between primary care appointment rates and their determinants, including workforce composition and the age structure of registered patients, have changed after the COVID-19 pandemic. We conducted longitudinal analysis on the 106 Clinical Commissioning Groups (CCGs) in England over two periods of 24 months (March 2018 to February 2020 and March 2021 to February 2023). We used fixed-effects regression models to relate monthly general practice appointment rates per registered patient to workforce size and composition and population age structure, and compared the results between the two periods.ResultsIn the pre-pandemic period, changes in full time equivalent (FTE) numbers of GP trainees and nurses were the only time-varying variables associated with appointment rates. In the post-lockdown period, the age profile of registered patients became a key determinant of appointment rates. A 1% increase in the proportion of registered patients over 80 years was associated with a 0.165 (38.7%) increase in appointments per patient per month. Changes in FTE numbers of qualified GPs and direct patient care staff were not found to influence the appointment rate in either period.ConclusionThe relationships between primary care appointment rates and the workforce composition and population age structure have changed following the COVID-19 pandemic. The proportion of registered patients over the age of 80 years is now the most significant time-varying driver of appointment rates. General practices serving older patients may face much higher demand and have a bigger challenge providing sufficient appointments in the future compared to before the pandemic.

Numerical threshold of split-step θ methods for stochastic age-structured population models

Numerical threshold of split-step θ methods for stochastic age-structured population models

Dengue transmission model in an age-structured population using delay differential equations

A mathematical model is presented in this article to describe the transmission of dengue in a population with varied age groups. The model is formulated using a system of delay differential equations. The model incorporates several factors such as the age distribution of the human population, including both juveniles and adults, as well as vector control measures, human knowledge of self-defense, and the latent delay for both humans and vectors. To assess the stability of the sickness-free equilibrium and do sensitivity analysis on the model, we calculate the basic reproduction number using the next-generation matrix technique. Furthermore, the numerical simulations are shown as evidence to support the theoretical findings. A thorough analysis is conducted to explore several control measures that seek to minimize the rate at which vectors bite humans, while ensuring sufficient protection against disease transmission within the population.

The Interaction between Population Age Structure and Policy Interventions on the Spread of COVID-19

The Interaction between Population Age Structure and Policy Interventions on the Spread of COVID-19

An age-structured syphilis model, II: optimal control and numerical simulation

The World Health Organization estimated that 8 million adults between 15 and 49 years old acquired syphilis globally in 2022. China CDC reported that there were 530 116 cases of syphilis in mainland China in 2023. Since syphilis is a sexually transmitted disease and age structure of the host population plays a crucial role, in this series of two papers we develop an age-structured model with four infection stages (primary, secondary, latent and tertiary) to study the transmission dynamics of syphilis. In part I (Wu et al . 2025 Proc. R. Soc. A 481 : 20240218 (doi: 10.1098/rspa.2024.0218 )), we investigated the well-posedness of the model and studied stability of the steady states. In part II, first, we consider the optimal control of the age-structured model. Second, utilizing the Markov Chain Monte Carlo method, we calibrate the reported syphilis data in China by using a demographic model. Finally, we apply the relevant simulation results to numerically simulate the age-structured model. Our results indicate that (i) for the syphilis demographic model, the basic reproduction number R 0 ≈ 2.4876 with CI (95%) (1.6823, 3.1434); (ii) tertiary stage infection is more severe in the elderly population; (iii) reducing the number of secondary and latent stage syphilis individuals can effectively reduce the total number of infected populations.

Scaling COVID-19 rates with population size in the United States.

Using county-level data from the United States, we assessed allometric scaling relationships of coronavirus disease (COVID-19) cases, deaths and age structure within and across the first four major waves of the pandemic (wild-type, alpha, delta, omicron). Results generally indicate that the burden of cases disproportionately impacted larger-sized counties, while the burden of deaths disproportionately impacted smaller counties. This may be partially due to multiple interacting social mechanisms, including a higher proportion of older adults who live in smaller counties. Moreover, these likely social mechanisms interacting with vaccinations and virus waves created a dynamic pattern whereby the rate and magnitude of infections and deaths were population- and time-dependent. Our results offer a novel perspective on the scaling dynamics of infectious diseases, highlighting how both the rate and magnitude of COVID-19 cases and deaths scale differently across counties. Population size and age structure are key factors in predicting disease burden. Our findings have practical implications, suggesting that scaling-informed public health policies could more effectively allocate resources and interventions to mitigate the impact of future epidemics across heterogeneous populations.

Equivalence of Stock-Recruitment Functions and Parent-Progeny Relationships in Discrete-Time Multi-Stage Models

Understanding the relationship between adult fish populations (the "stock") and the number of new fish entering the population (the "recruits") is essential for effective fisheries management. Traditionally, this relationship is represented by a stock-recruitment (SR) function, which is a simplified mathematical model that directly links stock size to recruitment. However, fish populations pass through several life stages, each stage influenced by unique population dynamic factors. Current SR functions often overlook these complexities, assuming that recruitment depends solely on the adult population size. In this study, we use a multi-stage, age-structured discrete-time population dynamic model that accounts for all life stages and the transitions between them. We demonstrate that, in general, a closed-form, univariate SR function may not accurately represent the recruitment process when these life stages are considered. Instead, we identify specific mathematical conditions under which a SR function is equivalent to our multi-stage model. Our findings suggest a re-evaluation of conventional SR models, advocating for multi-stage approaches to support fisheries management decisions.

Population Aging and the Dynamics of Housing Demand: An Empirical Analysis Based on Population Age Structure

Population Aging and the Dynamics of Housing Demand: An Empirical Analysis Based on Population Age Structure