When Birth Rates Decline, What Happens to a Given Population?

Human Population Growth and Family Planning

Richard E. Jones , Kristin H. Lopez , in Human Reproductive Biology (Third Edition), 2006

Birth Charge per unit

Birth rate is the number of individuals born in a population in a given amount of time. Human birth rate is stated every bit the number of individuals built-in per yr per 1000 in the population. For instance, if 35 births occur per year per grand individuals, the nativity charge per unit is 35. Oftentimes this rate is expressed equally a percentage, in this example 3.5 per 100, or 3.5%. Populations can be subdivided into juveniles (before puberty), reproductive adults, and postreproductive adults (those too one-time to have offspring). The younger a population, the faster that population grows because the birth rate is higher and the expiry rate is lower (Fig. 13-1). When birth rate is expressed per historic period group, it is called the standardized birth rate, as opposed to the crude birth rate of the total population.

Effigy thirteen-1. Three types of age pyramids. (a) Population is growing considering of a large proportion of juveniles. (b) The population is stable; notation the similar proportion of reproductive adults and juveniles and the relatively large proportion of postreproductive adults compared with (a). (c) Population is declining considering the preponderance of postreproductive adults ways that the decease rate is high, while the birth rate is low.

Read full affiliate

URL:

https://world wide web.sciencedirect.com/scientific discipline/commodity/pii/B9780080508368500172

FORMALISATIONS OF EVOLUTIONARY BIOLOGY

Paul Thompson , in Philosophy of Biological science, 2007

Including Age Stratification

Birth and death rates, the basis for determining r, may depend on age. For these populations, age-specific fecundities and probabilities of survival are important. To sketch how this parameter (age) can be incorporated, I assume, for simplicity, that for each historic period category fecundity and probability of survival are constant (discarding this assumption simply increases the mathematical complexity) ⁴⁷ .

Consider a population which breeds one time a year and in which the birth-rate is heavily dependent on the number of breeding females. A census is taken each twelvemonth prior to breeding.

Let:

due northx(t)	=	the number of females of historic period x in year t (x ranging from 0 to ω)
Px	=	probability that a female person aged ten in year t survives until year t +1
thousandx	=	boilerplate number of female person offspring produced past a female aged x
ften	=	number of these offspring surviving to historic period 1

Then:

f_x = P ₀ m _x, where P ₀ is the probability of a newborn (aged 0) will survive to age 1

If x > one, and then:

If x = 1, then:

${\mathrm{northward}}_1\left(t+1\right)=f_{\mathrm{i}}{\mathrm{north}}_1\left(t\right)+f_2{n}_2\left(t\right)+\mathrm{...}+f_{\mathrm{west}}{n}_w\left(t\right)$

Write n(t) for the vector {n₁(t), n₂(t), –, n_w (t)}, so the two equations tin can exist written in matrix course every bit: north(t+ane) = Ln(t)

where:

$L=\begin{array}{llllll}{f}_{\mathrm{i}}\hfill & f_2\hfill & f_3\hfill & \mathrm{...}\hfill & f_{w-1}\hfill & f_{\mathrm{two}}\hfill \\ P_{\mathrm{ane}}\hfill & 0\hfill & 0\hfill & \mathrm{...}\hfill & 0\hfill & 0\hfill \\ 0\hfill & P_2\hfill & 0\hfill & \mathrm{...}\hfill & 0\hfill & 0\hfill \\ 0\hfill & 0\hfill & P_2\hfill & \mathrm{...}\hfill & 0\hfill & 0\hfill \\ .\hfill & .\hfill & .\hfill & \mathrm{...}\hfill & .\hfill & .\hfill \\ .\hfill & .\hfill & .\hfill & \mathrm{...}\hfill & .\hfill & .\hfill \\ 0\hfill & 0\hfill & 0\hfill & \mathrm{...}\hfill & P_{\mathrm{westward}-\mathrm{one}}\hfill & 0\hfill \end{array}$

The offset row contains net fecundities, the diagonal of P_xsouthward contains survival probabilities. This is known every bit the Leslie matrix recognizing its promoter in ecology, P. H. Leslie, and is an age-classified model growth rate. If some other factor is more important than historic period (e.m., size) a more complex matrix can be constructed. ⁴⁸

The above provides an elementary glimpse at the rich mathematical appliance employed in formalising the dynamics of population ecology systems. At that place is a wealth of literature on mathematical models in environmental. An excellent starting place is John Maynard Smith'south piffling book Models in Ecology [1974].

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B978044451543850023X

Doctors and Demography

D F HAWKINS DSc, PhD, MB, BS(Lond), Medico(Mass), FRCOG, FACOG , Grand K ELDER MB, ChB, MD, FRCS, FRCOG , in Human being Fertility Control, 1979

Life-expectancy and the Nascency Rate

The birth rate required for a stationary population depends on the prevailing death charge per unit, which is related to life-expectancy. If long life is valued (in many cultures it has non been) and decease control is established, so either the nascence rate must come down to match the new decease rate, or population must ascent. Equally population cannot rise indefinitely the birth rate must come down anyway – information technology is a question of when, rather than whether – or else deaths must rise again and life-expectancy reject.

Figure 21.iii shows the relationship between life-expectancy and nascency and the rough decease charge per unit. The latter (in a stable population – an important proviso) is obtained by dividing thou past the life-expectancy at nascency. The expectancy of 20 years, which appears to have characterised the Stone Historic period, would give a decease charge per unit of 50 per 1000 per year. This in turn would necessitate 50 births per 1000 per year – about iv times the present level in Great Britain – simply to prevent a refuse in numbers.

Figure 21.iii. Relation between life-expectancy at birth (years) and crude death charge per unit.

The average (male and female) life-expectancy at nativity in Great Britain in 1978, nigh 72.5 years, would requite a crude death rate of thirteen.8 per one thousand population per year in a stable population and requires, of class, a rough nativity charge per unit of the same figure to give a stationary population. The latter effigy is the maximum we should aim for at nowadays, and we should farther reduce information technology if life-expectancy continues to increase. A few straws in the wind bespeak that it may even decrease.

Read total chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780407001275500258

Maternal Age and Pregnancy

Gabriella Pridjian , in Encyclopedia of Infant and Early on Childhood Development (Second Edition), 2020

Birth Trends

The overall birth rate in the US has decreased in the final four years; the actual birth rate fell to a 32-year low in 2018 at 3,788,235 births, down two% from 2017 births ( National Vital Statistics, 2019). Many factors influence birth rates. Many couples choose to wait until they are older to accept children for more economic security. Young couples may not make plans to accept a family unit unless they are optimistic near the future. Some women in the workforce do not have time to accept a baby and tin can't afford to pay for good quality childcare. Furthermore, more couples at present choose not to take children at all.

While the US nativity rate overall is decreasing, the nativity charge per unit in older mothers is increasing. Women are delaying childbirth. First-fourth dimension mothers tend to be older in metropolitan areas and on the coasts and younger in rural areas and in the Dandy Plains and the South (Ely et al., 2018a).

The teen and young developed (ages 12–19) birth rate reached a historic depression at 18.8 per 1000 in 2017 (National Vital Statistics, 2018). This subtract was mainly due to a decrease in unwanted pregnancies and an increase in utilize of contraception, particularly long-acting, reversible contraceptives (LARC) in this age group. The nearly mutual LARC contraceptives are intrauterine devices (IUDs) and implantable progestin capsules placed under the pare of the upper arm. This United States tendency was noted as early equally 2002 (Santelli et al., 2007) and continues in contempo years as nascence control availability and use continues to improve.

Birth rates continue to decline for almost all age groups of women nether historic period 35 but rising for women in their late 30s and early 40s (National Vital Statistics, 2019).

Read full chapter

URL:

https://world wide web.sciencedirect.com/scientific discipline/article/pii/B9780128093245222918

Futurity directions

A. Linn Murphree , in Clinical Ophthalmic Oncology, 2007

High birth rate and high retinoblastoma incidence rate in developing countries

The birth rate in most of the countries in the developed earth is no longer sufficient to maintain the current population. In contrast to a fertility rate of less than two (the number of children per average mother) in adult countries, in some countries of Africa the fertility charge per unit is as loftier equally six ( Fig. 83-1). Nearly 90% of the globe's births occur in economically underdeveloped countries. When that is combined with an incidence rate four times higher than in developed countries, the estimate of 20 000 cases of retinoblastoma worldwide is easier to empathize.

Read total affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9781416031673500887

The Sexual Health of Adolescents

Lori A.J. Scott-Sheldon , Blair T. Johnson , in Handbook of Child and Boyish Sexuality, 2013

Unintended Pregnancy

Pregnancy and nascence rates amidst teenagers in the Usa are the highest of all developed countries ( Bearinger, Sieving, Ferguson, & Sharma, 2007; Santelli & Melnikas, 2010). Teenage pregnancy is associated with adverse wellness, social, and economical consequences for children, parents, and guild at large (Hoffman, 2006). The estimated total annual price associated with teenage childbearing in the United states is $10.9 billion (The National Campaign to Prevent Teen and Unplanned Pregnancy, 2011). While these costs are staggering, pregnancy and nascency rates have declined in the Usa since the 1950s, saving billions of dollars (Hoffman, 2006; Santelli & Melnikas, 2010). Subsequently a cursory rise in the United States, nascence rates for teenage females, aged 15 to 19, fell eight% from 2007 to 2009—reaching a historic low of 39 births per i,000 in this historic period grouping (Ventura & Hamilton, 2011). Birth rates have fallen for all ethnic groups, but rates amid African American, Hispanic, and Native American adolescents remain significantly higher than those for white and Asian adolescents (Ventura & Hamilton, 2011). Reductions in sexual activity and increased condom and contraceptive employ accept contributed to the recent declines in teenage pregnancy (for a review, see Santelli & Melnikas, 2010).

Read total chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B978012387759800009X

Handbook of Object Novelty Recognition

Sara N. Burke , Carol A. Barnes , in Handbook of Behavioral Neuroscience, 2018

1 Introduction

Failing birth rates and an increased life expectancy have resulted in a worldwide shift in the population age distribution. In fact, at that place are more adults over the historic period of 65 than has ever occurred in recorded history. This demographic reality makes it imperative to gain a deeper understanding of how avant-garde age impacts the brain and noesis of older individuals. Although ageing affects the entire torso, its impact on behaviour is something that individuals outside of the field of gerontology can appreciate because we all have personal anecdotes of 'forgetfulness'. Moreover, the frequency of episodes of memory lapse increases with avant-garde age, and self-reports of these incidents become more mutual. In fact, the famous Canadian psychologist D.O. Hebb, well known for his neuropsychological postulate of jail cell assembly germination and behaviour, wrote a personal business relationship of the types of intellectual change one tin face in advanced age. Hebb's first description of what he termed a 'retentivity blackout' occurred when he was 47:

I was reading a journal article that was straight relevant to some piece of work I had underway or was proposing to try. I thought, 'I must make a note of this', simply when I turned the page, I found a pencilled notation in my handwriting! It was a real shock. I was used to forgetting things that didn't interest me, but even then I ever knew when I was reading something a second time.

Hebb (1978)

Later, when Hebb was in his mid-70s he noted that his forgetfulness had increased, writing 'I have long believed that the best way to remember to take something with me is to put it on the doorstep, so I see it when I leave; now this works better if the object is big enough to trip me' (Hebb, 1978). Because personal accounts of contradistinct memory during ageing are pervasive, it is not surprising that research on the neurobiology of ageing has focused on brain structures known to be critical for memory germination, such as the hippocampus (Scoville and Milner, 1957; Morris et al., 1982).

While decades of research on the neurobiology of age-related memory decline has implicated the hippocampus in this dysfunction (Barnes, 1979; for review, see Rosenzweig and Barnes, 2003), relatively less is known regarding the touch of normal ageing on other temporal lobe structures, such as the perirhinal, entorhinal and postrhinal/parahippocampal cortices of the parahippocampal region. Although the link between historic period-associated physiological changes in the hippocampus and behaviour is irrefutable (for review, come across Rosenzweig and Barnes, 2003; Burke and Barnes, 2006; Wilson et al., 2006; Gray and Barnes, 2015), the hippocampus does not age in isolation. In fact, the density of reciprocal projections between the hippocampus and parahippocampal areas (van Strien et al 2009;., Agster and Burwell, 2013; Binicewicz et al., 2016) highlights how hippocampal cellular alterations could sally from dysfunction in another region or could provoke adaptive bounty to maintain network output (Gray and Barnes, 2015).

The parahippocampal region in mammals is comprises the cortical areas that surround the hippocampus, including the perirhinal cortex, parahippocampal cortex, entorhinal cortices, presubiculum and parasubiculum (van Strien et al., 2009). The primate parahippocampal cortex is homologous to the rodent postrhinal cortex (Burwell et al., 1995). There are several observations that support the hypothesis that the parahippocampal region is also impacted past normative ageing processes. These include human being and other animal studies that have implicated the perirhinal cortex as a region of the brain that is also vulnerable in advanced historic period. For example, older adults (Davidson and Glisky, 2002; Koen and Yonelinas, 2014, 2016), old monkeys (Moss et al., 1988, 1997; Rapp and Amaral, 1991; Herndon et al., 1997; Shamy et al., 2006) and aged rats (Bartolini et al., 1996; Wiig and Burwell, 1998; de Lima et al., 2005; Pieta Dias et al., 2007; Platano et al., 2008) show reduced perirhinal cortical–dependent object recognition relative to younger individuals tested. While the interest of the hippocampus in this cognitive part is heavily debated (for example, see Squire et al., 2007; Brown, 2008), information technology is widely accustomed and clear from all the bachelor lesion data that the perirhinal cortex is necessary for object recognition (e.g., Ennaceur et al., 1996; Ennaceur and Aggleton, 1997; Baxter and Murray, 2001a,b; Prusky et al., 2004; Winters et al., 2004; Norman and Eacott, 2005; Winters and Bussey, 2005).

Here, we nowadays a comprehensive review of object recognition impairments in ageing, highlighting comparisons across species. Central to this discussion is the role of perirhinal cortical office in normal cognition, which is a topic that continues to be discussed and actively researched in humans and in creature models. Specifically, some have argued that the perirhinal cortex participates in a medial temporal lobe memory system by providing a familiarity betoken, simply that it does not significantly contribute to perception (i.e., the memory framework; Squire and Zola-Morgan, 1991; Buffalo et al., 1998; Eichenbaum, 2000; Squire et al., 2004; Eichenbaum et al., 2007; Suzuki, 2009; Suzuki and Baxter, 2009; Clark et al., 2011). In dissimilarity, others have argued that the perirhinal cortex serves a perceptual mnemonic role, by bounden together features represented in lower cortical areas (Fig. 20.1; Murray and Bussey, 1999; Bussey et al., 2003; Buckley, 2005; Bartko et al., 2007b; i.east., the perceptual-mnemonic framework, Bartko et al., 2007a; Baxter, 2009; Suzuki and Baxter, 2009). Under the perceptual-mnemonic framework, the binding of information represented across disparate areas of the neocortex is believed to be the cornerstone of retentivity. Thus, behavioural deficits resulting from perirhinal cortical lesions tin present either equally memory or perception impairments depending on the specific chore demands. The sentiments of this contend are echoed in the controversy regarding the vulnerability of the perirhinal cortex to age-related decline. In the memory framework, the observation is emphasized that the power to identify a previously experienced stimulus every bit familiar is not contradistinct with avant-garde age (Robitsek et al., 2008; Koen and Yonelinas, 2014, 2016). Conversely, in the perceptual-mnemonic framework, it is emphasized that older adults (Toner et al., 2009; Stark et al., 2010, 2013, 2015; Yassa et al., 2010; Ryan et al., 2012; Trelle et al., 2017) and other animals (Burke et al., 2011; Johnson et al., 2017) are impaired at discriminating betwixt stimuli that share features. These age-related discrimination impairments could arise from impaired representations of sensory details that are needed to disambiguate stimuli that share features (Shush et al., 2018). This chapter provides a framework in which to reconcile these 2 seemingly disparate views on how historic period-related deficits in object recognition due to impaired bigotry can co-occur with intact familiarity processes.

Figure twenty.1. The perceptual-mnemonic framework of perirhinal cortical function.

The proposed convergence of object feature representations as data passes through sequential processing stages in the ventral visual stream (Murray and Bussey, 1999). Individual LEGO blocks represent uncomplicated visual features encoded in early regions of the ventral visual stream. These features combine to form representations of increasing complexity in association cortical areas, such as junior temporal cortex. These features are then bound together in perirhinal cortex.

Read full chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780128120125000203

The Microbiome in Wellness and Affliction

Emilee Parsons , ... Elaine O. Petrof , in Progress in Molecular Biology and Translational Science, 2020

1 Introduction

Preterm birth rates and resultant morbidity and mortality from complications of prematurity go along to ascension despite continued comeback of maternal and neonatal intendance. Preterm neonates of less than 32 weeks gestation with birth weights nether 1500  1000 are particularly vulnerable to medical complications such as necrotizing enterocolitis (NEC), interventricular hemorrhage, infection, and bronchopulmonary dysplasia. All these aforementioned complications increase the risk of poor neurodevelopmental outcomes in this population such equally cerebral palsy, hearing and vision impairment, and learning disabilities. The overall incidence of neurodevelopment damage in premature infants remains high, with increasing incidence in growth restricted infants and earlier gestational ages. While the causes of these morbidities are multifactorial, in that location is increasing interest in the role the microbiome may play in their development. In particular, several studies have indicated a role for the microbiome in NEC. ^ane–3 Furthermore, there is accumulating evidence of a connectedness betwixt the microbiome and neurodevelopment. Understanding links amid microbiome, morbidities, and neurodevelopment may enable interventions to improve preterm babe outcomes. Information technology is well known the microbiome of a preterm infant differs from a term infant in terms of overall multifariousness and dominant species of bacteria. In addition, since brain and microbiome development occur in parallel in neonates, there are potential therapeutic target windows of time for possible protective strategies for these processes. The microbiome has been linked to other neurologic conditions such as autism, schizophrenia, and Alzheimer's disease. ^4–6 Yet, the bear on of the microbiome on the developing encephalon in preterm infants is largely unknown.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/S187711732030051X

Health Psychology

Beth Alder , in Comprehensive Clinical Psychology, 1998

8.16.2.1 Current Contraceptive Use

The nascence rate in the Western world has fallen dramatically since the 1940s ( Scambler, 1997). Information technology is not clear to what extent this is because of the increase in education of women, relative affluence, parental choice, or provision of contraceptive advice and supplies. In the European union the fertility rate measured in births per thousand women barbarous from 2.4 in 1970 to 1.5 in 1992. In 1993, 39% of women betwixt sixteen and 35 used the pill. Contraceptive use is shown in Tabular array 1 (Social Trends, 1995).

Table 1. Contraceptive use in 1993 in the United Kingdom (Social Trends, 1995).

Method	Percentage of users anile sixteen-49   years
Oral contraceptive pill	25
Condom	17
Hysterectomy	12
Vasectomy/sterilization	12
IUD	5
Withdrawal	3
Other	3

The bear witness for a contraceptive career (Lindemann, 1977) suggests that young people utilise condoms or no method at all in their first sexual encounters (Abraham & Sheeran, 1994). With increasing sexual and contraceptive feel they move to oral contraceptives. Afterwards the nativity of their starting time child, they change to intrauterine device (IUD) and, afterward their family unit is considered to exist complete, they choose either male person or female person sterilization. Oddens (1996), in a population survey of contraceptive use in the United kingdom of great britain and northern ireland and Germany, establish that patterns of contraception use were closely related to variables such every bit age, parity, marital status, and intention to have children. Age and the desire to have children are the major factors associated with contraceptive pick. The pass up in the use of oral contraceptives with age has been related to perceptions of health risk. In 1989 a "pill scare" in Germany associated certain pills with an increased take chances of thromboembolism and this was followed by a fall in the number of oral contraceptive users. This happened again in the UK in October 1995 (Martin, Hilton, & Kerry, 1997). A comparison of the major reasons given for choosing different contraceptives is given in Table 2.

Table 2. Motives for choosing contraceptive method currently used (percentage). More than one answer could be given. Deutschland, n = 1064; UK, n = 967.

Reason	Oral contraception		Condom/diaphragm		IUD		Sterilization (vasectomy and laparascopic)
	Germany	UK	Germany	UK	Germany	UK	Germany	United kingdom of great britain and northern ireland
Reliability	94	88	34	45	66	69	52	64
Nondisturbance of sex life	62	65	18	8	83	48	20	38
Piece of cake to use	51	69	27	40	41	47	2	7
Menstrual bug	33	29	0	1	3	1	4	1
Medical advice	21	12	4	seven	43	39	32	fourteen
Infrequent intercourse	2	1	26	fifteen	21	2	0	2
Health concerns	1	2	36	32	21	11	34	eighteen
Partner interest	2	0	23	11	0	0	xv	12
Problems with quondam method	iii	7	30	37	39	40	33	16

Source: Oddens et al. (1994a, 1994b).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B0080427073002388

HIV and Fertility

B. Zaba , S. Gregson , in International Encyclopedia of the Social & Behavioral Sciences, 2001

1.iv Changes in Population Construction

Changes in the nascence rate can come nigh not only because of changes in historic period-specific fertility rates but besides because of structural changes in the population. Gregson et al. ( 1999) showed that HIV-related bloodshed will tend to brand the population structure younger, and with proportionately more women in the superlative childbearing ages of xx–29 this would tend to push up the rough nascence charge per unit. Similarly, over time, the excess mortality suffered by HIV-positive women with primary or secondary sterility due to coinfection with other STDs would tend to raise the proportion of fecund women in the population and thereby enhance the overall birth charge per unit, fifty-fifty if the fertility rates of HIV-positive and HIV-negative women did non change. Fecundity could as well rise if interventions to treat classical STDs were successful.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B0080430767022221

westknetch.blogspot.com

Source: https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/birth-rate

Share this post