A note on the reduction of a risk of death

Abstract

Methods for assessing the gain of life expectancy by reducing the risks of death are examined. Depending on the method used, overestimation and underestimation of life expectancy may occur. Although the gain in life expectancy is not a linear function of the per cent reduction in mortality, a linear approximation may be used when the mortality rate is low. When the mortality rate is high, linear approximations tend to overestimate the years gained. A method using the parameter H⁽ⁱ⁾ developed by Keyfitz (1977) is adequate for low mortality rates such as with neoplasms. However, when mortality rates are high, as they are for cardiovascular‐renal diseases (CVD), Keyfitz's method tends to underestimate the gain in life expectancy. For CVD, Keyfitz's estimation is adequate below the 20 per cent reduction range. The magnitude of overestimation and underestimation are numerically evaluated based on the 1964 United States male mortality statistics.     

Life expectancy (ex ) and stable age distribution (Cx ) of Plutella xylostella (L.) (Lep.: Yponomeutidae), exposed to sublethal doses of hexaflumuron

The diamondback moth, Plutella xylostella (L.) is a major pest of crucifers in Iran. In this study, the influence of two sublethal concentrations (LC₁₀ and LC₂₅) of an insect growth regulator, hexaflumuron on life expectancy (e _x ), stable age distribution (C _x ), age-specific fertility (m _x ) and number of fertile eggs per day was investigated. Results showed that the sublethal doses of hexaflumuron decreased life expectancy (e _x ), age-specific fertility (m _x ) and number of fertile eggs per day of P. xylostella. Also stable age distribution (C _x ) of population in next generation was changed and rate of adults in sublethals was increased compared to control. According obtained results, hexaflumuron is a good choice for IPM strategy in controlling the diamondback moth.     

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus II. An assessment of the chronic toxicity of lindane and 3,4-dichloroaniline using life tables

The effects of chronic exposure of the freshwater rotifer Brachionus calyciflorus to the toxicants lindane and 3,4-dichloroaniline (DCA), were evaluated. The parameters used to determine the toxicity on these compounds were the age-specific and fertility, and the demographic parameters: intrinsic rate of natural increase (r), generation time (T), net reproductive rate (R _o), reproductive value (V _x) and life expectancy (e _o). All the demographic parameters studied decreased with increasing toxicant concentrations. The use of life tables techniques with B. calyciflorus as a test method for the determination of chronic toxicity of xenobiotics is discussed.     

Reproductive parameters and life expectancy of Tetranychus urticae (Acari: Tetranychidae) on 12 genotypes of melon and cucumber in laboratory condition

The effect of two host plant species including eight genotypes of melon (Cucumis melo L.) and four genotypes of cucumber (Cucumis sativus L.) was studied on reproductive parameters: life expectancy and mortality of Tetranychus urticae (Koch) at 25?±?1?°C, 60?±?5% rh and a photoperiod of 16L:8D hours. The results indicated that the highest value of the gross fecundity rate of T. urticae was 96.72?±?16.70 (eggs/female) on Mir sultan and the lowest value was 14.33?±?0.88 on Ananasi. The maximum value of gross fertility rate (41.55?±?4.79) was recorded on Sultan, while the minimum value (1.38?±?0.08) was recorded on Ananasi. The net fecundity rate was varied from 0.47?±?0.09 on Ananasi to 23.53?±?3.96 eggs/female on Sultan. The net fertility rate was 12.96?±?2.18 on Sultan and 0.04?±?0.009 on Ananasi, which was the maximum and minimum values, respectively. The range of gross hatch rate on different melon and cucumber genotypes was 9.67% on Ananasi to 72.46% on Super sultan. The cohort reared on Super sultan had the highest mean eggs per day and those on Shah abadi had the lowest mean eggs per day. In addition, the mite demonstrated the maximum value of mean fertile eggs per day with the amount of 1.66?±?0.19 eggs/female when fed on Sultan, and Ananasi demonstrated the minimum value (0.09?±?0.005). The life expectancy of one-day-old adults of T. urticae was estimated to be 16?days on Garmak Isfahan and 26.62 days on Mir sultan which is the maximum and minimum values, respectively. Furthermore, the highest mortality percentage of immature stages of T. urticae was recorded on Ananasi and the lowest was recorded on Super sultan. Comparison of the data collected in this study revealed that the mites had considerably better performance on cucumber genotypes than melon genotypes, so we can assume that cucumber is the preferable host species for T. urticae. The use of preferable and resistant host plants is helpful in crop rotation and it will be one of the beneficial strategies to integrated pest management programmes.     

A period analysis of parity distribution among white and nonwhite women in the United States, 1940–1974

Abstract

The historical trends of childlessness and of one‐child, two‐child, and three‐or‐more‐child families among white and nonwhite women in the United States are studied in terms of period fertility tables. Given the age and parity of a woman, we can read from the fertility tables how her parity is expected to change at successive ages during the rest of her childbearing period, if she is subjected to the age‐parity‐specific fertility rates for a particular year. The fertility tables for white and nonwhite women are constructed for the years 1940, 19S0, 1960, 1970, and 1974. These tables show that among white women who have completed their childbearing (with period rates), the percentage with more than two children has decreased from 66 in 1960 to 27 in 1974, whereas the corresponding reduction among nonwhite women is from 67 to 48 per cent (Table 1, Case 1).     

Demographic parameters of Brachionus calyciflorus Pallas (Rotifers) exposed to sublethal endosulfan concentrations

The effects of sublethal levels of endosulfan (0, 1, 1.5, 2.5 and 3.3 mg 1^–1) on the demography of the rotifer Brachionus calyciorus were studied. Life expectancy at birth (e _o), net reproductive rate (Ro), generation time (T) and intrinsic rate of natural increase (r) were significant differentes between blank controls and controls with acetone. The effective endosulfan concentration at which a given parameter value was reduced to 50% of the controls (EC50) was calculated for life expectancy.     

Mass HIV Treatment and Sex Disparities in Life Expectancy: Demographic Surveillance in Rural South Africa

Background

Women have better patient outcomes in HIV care and treatment than men in sub-Saharan Africa. We assessed—at the population level—whether and to what extent mass HIV treatment is associated with changes in sex disparities in adult life expectancy, a summary metric of survival capturing mortality across the full cascade of HIV care. We also determined sex-specific trends in HIV mortality and the distribution of HIV-related deaths in men and women prior to and at each stage of the clinical cascade.

Methods and Findings

Data were collected on all deaths occurring from 2001 to 2011 in a large population-based surveillance cohort (52,964 women and 45,688 men, ages 15 y and older) in rural KwaZulu-Natal, South Africa. Cause of death was ascertained by verbal autopsy (93% response rate). Demographic data were linked at the individual level to clinical records from the public sector HIV treatment and care program that serves the region. Annual rates of HIV-related mortality were assessed for men and women separately, and female-to-male rate ratios were estimated in exponential hazard models. Sex-specific trends in adult life expectancy and HIV-cause-deleted adult life expectancy were calculated. The proportions of HIV deaths that accrued to men and women at different stages in the HIV cascade of care were estimated annually.Following the beginning of HIV treatment scale-up in 2004, HIV mortality declined among both men and women. Female adult life expectancy increased from 51.3 y (95% CI 49.7, 52.8) in 2003 to 64.5 y (95% CI 62.7, 66.4) in 2011, a gain of 13.2 y. Male adult life expectancy increased from 46.9 y (95% CI 45.6, 48.2) in 2003 to 55.9 y (95% CI 54.3, 57.5) in 2011, a gain of 9.0 y. The gap between female and male adult life expectancy doubled, from 4.4 y in 2003 to 8.6 y in 2011, a difference of 4.3 y (95% CI 0.9, 7.6). For women, HIV mortality declined from 1.60 deaths per 100 person-years (95% CI 1.46, 1.75) in 2003 to 0.56 per 100 person-years (95% CI 0.48, 0.65) in 2011. For men, HIV-related mortality declined from 1.71 per 100 person-years (95% CI 1.55, 1.88) to 0.76 per 100 person-years (95% CI 0.67, 0.87) in the same period. The female-to-male rate ratio for HIV mortality declined from 0.93 (95% CI 0.82–1.07) in 2003 to 0.73 (95% CI 0.60–0.89) in 2011, a statistically significant decline (p = 0.046). In 2011, 57% and 41% of HIV-related deaths occurred among men and women, respectively, who had never sought care for HIV in spite of the widespread availability of free HIV treatment. The results presented here come from a poor rural setting in southern Africa with high HIV prevalence and high HIV treatment coverage; broader generalizability is unknown. Additionally, factors other than HIV treatment scale-up may have influenced population mortality trends.

Conclusions

Mass HIV treatment has been accompanied by faster declines in HIV mortality among women than men and a growing female–male disparity in adult life expectancy at the population level. In 2011, over half of male HIV deaths occurred in men who had never sought clinical HIV care. Interventions to increase HIV testing and linkage to care among men are urgently needed.     

Health,income, and the preston curve: A long view

Well-being is increasingly viewed as a multidimensional phenomenon, of which income is only one facet. In this paper I focus on another one, health, and look at its synthetic measure, life expectancy at birth, and its relationship with per capita income. International trends of life expectancy and per capita GDP differed during the past 150 years. Life expectancy gains depended on economic growth but also on the advancement in medical knowledge. The pace and breadth of the health transitions drove life expectancy aggregate tendencies and distribution. The new results confirm the relationship between life expectancy and per capita income and its outward shift over time as put forward by Samuel Preston. However, the association between nonlinearly transformed life expectancy and the log of per capita income does not flatten out over time, but becomes convex suggesting more than proportional increases in life expectancy at higher per capita income levels.     

The influence of the medical care on the human life expectancy in 20th century and the Penna ageing model

Summary The expression of many genetic defects may be suppressed by proper medical care or even by changing the environmental conditions. We have used the Penna model of ageing to show that such efFects may be responsible for increasing the human life expectancy during the 20 ^th century. This effect is equivalent to the shift of the threshold (T) in the Penna model, which determines how many deleterious, expressed mutations kill an organism. For long genomes, the shift of T changes the age distribution significantly with negligible relative changes in the maximum life span, while for short genomes, the shift of T changes both, the age distribution as well as the maximum age. Unfortunately the same simulations show that the strategy of enhancing the medical care requires more and more effort to keep the mortality rate of our populations at the same lower level and that some new defects could be exposed to selection.     

Effects of mine acid on the longevity and reproductive rate of the gastrotricha Lepidodermella squammata (Dujardin)

Effects of mine acid on longevity and reproductive rate of the parthenogenic gastrotrich Lepidodermella squammata were studied under laboratory culture conditions. Water from unpolluted and polluted streams was used, directly or mixed, to establish a series of test conditions at pH 8.1, 7.1, 6.4, 5.2, 4.6 and 3.3. Eggs, cultured individually under each test condition, were observed at 12 h intervals for hatching, daughter egg laying and death. Data representing 50 animals under each test condition were used in the construction of a series of life tables. From these were calculated maximal life expectancy (e_x), net reproductive rate per individual lifetime (R_o) and intrinsic rate of natural increase (r_max).Values of e_x, R_o and r_max were maximal at pH 7.1 and were reduced slightly at the higher pH; e_x was greatly reduced and R_o zero at pH 6.4 and 5.2; and e_x was zero at pH 4.6 and 3.3. Analysis of variance tests indicate significant differences between e_x values of L. squammata cultured at pH 8.1 and those cultured at pH 7.1, but no differences between R_o or r_max.Associated with the decrease in pH was an increase in total conductivity and a decrease in carbonate alkalinity and hence in carbonate conductivity. It appears that L. squammata is capable of living and reproducing at pH 6.0 to 6.5 under field conditions low in carbonates, providing non-carbonate ions are not abundant, or under field conditions high in non-carbonate ions, providing sufficient carbonates are present.     

Life table demography and population growth of Brachionus variabilis Hempel, 1896 in relation to Chlorella vulgaris densities

We studied the life history variables and population growth characteristics of Brachionus variabilis, which was recorded for the first time from Mexico. The animals were fed Chlorella, using five concentrations (0.25, 0.5, 1, 2 and 4 × 10⁶ cells ml^–1) at 25 °C. Food density was observed to have significant effect on life expectancy, average lifespan, gross reproductive rate, net reproductive rate, generation time and population growth rate. The average lifespan ranged from 3 to 6 days depending on the food density. The net reproductive rate ranged from 2 to 7 neonates female^–1 d^–1. The rate of population increase per day varied from 0.14 to 0.35. The highest net reproductive rate and average lifespan and life expectancy were recorded at Chlorella concentrations of 1 × 10⁶ and 2 × 10⁶ cells ml^–1.     

Mortality among People with Severe Mental Disorders Who Reach Old Age: A Longitudinal Study of a Community-Representative Sample of 37892 Men

Background

Severe mental illnesses are leading causes of disability worldwide. Their prevalence declines with age, possibly due to premature death. It is unclear, however, if people with severe mental disorders who reach older age still have lower life expectancy compared with their peers and if their causes of death differ.

Methods and Findings

Cohort study of a community-representative sample of 37892 Australian men aged 65–85 years in 1996–1998. Follow up was censored on the 31st December 2010. Lifetime prevalence of schizophrenia spectrum, bipolar, depressive and alcohol-induced disorder was established through record linkage. A subsample of 12136 consented to a face-to-face assessment of sociodemographic, lifestyle and clinical variables. Information about causes of death was retrieved from the Australian Death Registry. The prevalence of schizophrenia spectrum, bipolar, depressive and alcohol-induced disorders was 1.2%, 0.3%, 2.5% and 1.8%. The mortality hazard for men with a severe mental disorder was 2.3 and their life expectancy was reduced by 3 years. Mortality rates increased with age, but the gap between men with and without severe mental disorders was not attenuated by age. Cardiovascular diseases and cancer were the most frequent causes of death. The excess mortality associated with severe mental disorders could not be explained by measured sociodemographic, lifestyle or clinical variables.

Conclusions

The excess mortality associated with severe mental disorders persists in later life, and the causes of death of younger and older people with severe mental disorders are similar. Hazardous lifestyle choices, suboptimal access to health care, poor compliance with treatments, and greater severity of medical comorbidities may all contribute to this increased mortality. Unlike young adults, most older people will visit their primary care physician at least once a year, offering health professionals an opportunity to intervene in order to minimise the harms associated with severe mental disorders.     

The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States

Background

Counties are the smallest unit for which mortality data are routinely available, allowing consistent and comparable long-term analysis of trends in health disparities. Average life expectancy has steadily increased in the United States but there is limited information on long-term mortality trends in the US counties This study aimed to investigate trends in county mortality and cross-county mortality disparities, including the contributions of specific diseases to county level mortality trends.

Methods and Findings

We used mortality statistics (from the National Center for Health Statistics [NCHS]) and population (from the US Census) to estimate sex-specific life expectancy for US counties for every year between 1961 and 1999. Data for analyses in subsequent years were not provided to us by the NCHS. We calculated different metrics of cross-county mortality disparity, and also grouped counties on the basis of whether their mortality changed favorably or unfavorably relative to the national average. We estimated the probability of death from specific diseases for counties with above- or below-average mortality performance. We simulated the effect of cross-county migration on each county''s life expectancy using a time-based simulation model. Between 1961 and 1999, the standard deviation (SD) of life expectancy across US counties was at its lowest in 1983, at 1.9 and 1.4 y for men and women, respectively. Cross-county life expectancy SD increased to 2.3 and 1.7 y in 1999. Between 1961 and 1983 no counties had a statistically significant increase in mortality; the major cause of mortality decline for both sexes was reduction in cardiovascular mortality. From 1983 to 1999, life expectancy declined significantly in 11 counties for men (by 1.3 y) and in 180 counties for women (by 1.3 y); another 48 (men) and 783 (women) counties had nonsignificant life expectancy decline. Life expectancy decline in both sexes was caused by increased mortality from lung cancer, chronic obstructive pulmonary disease (COPD), diabetes, and a range of other noncommunicable diseases, which were no longer compensated for by the decline in cardiovascular mortality. Higher HIV/AIDS and homicide deaths also contributed substantially to life expectancy decline for men, but not for women. Alternative specifications of the effects of migration showed that the rise in cross-county life expectancy SD was unlikely to be caused by migration.

Conclusions

There was a steady increase in mortality inequality across the US counties between 1983 and 1999, resulting from stagnation or increase in mortality among the worst-off segment of the population. Female mortality increased in a large number of counties, primarily because of chronic diseases related to smoking, overweight and obesity, and high blood pressure.     

Health transition: examples from the western Pacific.

The Industrial Revolution ushered in a rapid transition from agriculture to industrialization. Some biological effects of this transition included increasing life expectancy, reduced infant mortality, and some decline in fertility. Reduced infant mortality first brought about an increase in life expectancy, but as humans were able to control infectious diseases, child and adult mortality also decreased. Now, accidents and chronic diseases are responsible for most mortality in many age groups. This shift from infectious diseases to accidents and chronic diseases is called the health transition. Japan and US are Pacific Basin countries which have relatively high life expectancy and low infant mortality (1988, 75.54 years vs. 71.38 years, and 4.4 vs. 9.9, respectively). These figures suggest that these countries rather advanced in the health transition. Japan may have better life expectancy than the US because of the effect of environmental factors, ethnic diversity, and health care differentials by social class on cardiovascular disease and cancer mortality. China and Thailand hold intermediate positions (67.98 years (1985-1990) vs. 63.82 years (1985-1986), and 32.4 vs. 39, respectively). Some research indicates that urban conditions and factory work increase the cardiovascular disease risk among the Chinese. Recent research suggests that access to immunization and modern medical care for acute disease are the only critical variables of the health transition rather than other variables. Papua New Guinea is not progressing very well (53.18 years and 58). Papua New Guinea has not yet been able to control infectious diseases, especially malaria. This comparison illustrates that populations progress through the health transition at different rates.     

Sublethal effects of essential oil of Cinnamomum zeylanicum Blume on life expectancy (ex) and age-specific fertility (mx) of two-spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae)

Two-spotted spider mite, Tetranychus urticae Koch, is one of the most important pests of agricultural products that have a global distribution. Now, the control is dependent on the use of chemical pesticides. The effects of the sublethal concentrations (LC₁₀ and LC₂₅) of the essential oil of Cinnamomum zeylanicum were evaluated on some parameters of the life table of the pest, at the constant temperature of 30?°C, relative humidity of 40?±?5% and photoperiod of 16L: 8D. Our results showed that the essential oil of cinnamon is effective on female adult stage. Lethal concentration at which 50% mortality (LC₅₀) for the essential oils is from C. zeylanicum on female adult mite was 23.39?μl/L air. Sublethal concentrations of the essential oil of C. zeylanicum also impair the natural biology of the mite. Concentrations of sublethal of essential oil decreased age-specific fertility (m_x) of T. urticae compared with the control. Sublethal concentrations (LC₁₀ and LC₂₅) have reduced the life expectancy (e_x) in egg stage. Sublethal effects of the essential oil of C. zeylanicum and its impact on T. urticae management are discussed.     

The State of Health in Older Adults in Japan: Trends in Disability,Chronic Medical Conditions and Mortality

Both life expectancy and healthy life expectancy in Japan have been increasing and are among the highest in the world, but the gap between them has also been widening. To examine the recent trends in old age disability, chronic medical conditions and mortality in Japan, we retrospectively analyzed three nationally representative datasets: Comprehensive Survey of Living Conditions (2001–2013), Patient Survey (1996–2011) and Vital Statistics (1995–2010). We obtained the sex- and age-stratified trends in disability rate, treatment rates of nine selected chronic medical conditions (cerebrovascular diseases, joint disorders, fractures, osteoporosis, ischemic heart disease, diabetes mellitus, hypertension, pneumonia and malignant neoplasms), total mortality rate and mortality rates from specific causes (cerebrovascular diseases, heart diseases, pneumonia and malignant neoplasms) in both sexes in four age strata (65–69, 70–74, 75–79, 80–84 years). Disability rates declined significantly in both sexes. Treatment rates of all selected medical conditions also decreased significantly, except for fractures in women and pneumonia. Both total mortality rate and cause-specific mortality rates decreased in both sexes. We concluded that the recent decline in disability rates, treatment rates of chronic medical conditions and mortality rates points toward overall improvement in health conditions in adults over the age of 65 years in Japan. Nonetheless, considering the increase in the number of older adults, the absolute number of older adults with disability or chronic medical conditions will continue to increase and challenge medical and long-term care systems.     

The Invisible Cliff: Abrupt Imposition of Malthusian Equilibrium in a Natural-Fertility,Agrarian Society

Analysis of a natural fertility agrarian society with a multi-variate model of population ecology isolates three distinct phases of population growth following settlement of a new habitat: (1) a sometimes lengthy copial phase of surplus food production and constant vital rates; (2) a brief transition phase in which food shortages rapidly cause increased mortality and lessened fertility; and (3) a Malthusian phase of indefinite length in which vital rates and quality of life are depressed, sometimes strikingly so. Copial phase duration declines with increases in the size of the founding group, maximum life expectancy and fertility; it increases with habitat area and yield per hectare; and, it is unaffected by the sensitivity of vital rates to hunger. Transition phase duration is unaffected by size of founding population and area of settlement; it declines with yield, life expectancy, fertility and the sensitivity of vital rates to hunger. We characterize the transition phase as the Malthusian transition interval (MTI), in order to highlight how little time populations generally have to adjust. Under food-limited density dependence, the copial phase passes quickly to an equilibrium of grim Malthusian constraints, in the manner of a runner dashing over an invisible cliff. The three-phase pattern diverges from widely held intuitions based on standard Lotka-Verhulst approaches to population regulation, with implications for the analysis of socio-cultural evolution, agricultural intensification, bioarchaeological interpretation of food stress in prehistoric societies, and state-level collapse.     

Life expectancy,economic inequality,homicide, and reproductive timing in Chicago neighbourhoods.

In comparisons among Chicago neighbourhoods, homicide rates in 1988-93 varied more than 100-fold, while male life expectancy at birth ranged from 54 to 77 years, even with effects of homicide mortality removed. This "cause deleted" life expectancy was highly correlated with homicide rates; a measure of economic inequality added significant additional prediction, whereas median household income did not. Deaths from internal causes (diseases) show similar age patterns, despite different absolute levels, in the best and worst neighbourhoods, whereas deaths from external causes (homicide, accident, suicide) do not. As life expectancy declines across neighbourhoods, women reproduce earlier; by age 30, however, neighbourhood no longer affects age specific fertility. These results support the hypothesis that life expectancy itself may be a psychologically salient determinant of risk taking and the timing of life transitions.     

Repeated intraspecific divergence in life span and aging of African annual fishes along an aridity gradient

Life span and aging are substantially modified by natural selection. Across species, higher extrinsic (environmentally related) mortality (and hence shorter life expectancy) selects for the evolution of more rapid aging. However, among populations within species, high extrinsic mortality can lead to extended life span and slower aging as a consequence of condition‐dependent survival. Using within‐species contrasts of eight natural populations of Nothobranchius fishes in common garden experiments, we demonstrate that populations originating from dry regions (with short life expectancy) had shorter intrinsic life spans and a greater increase in mortality with age, more pronounced cellular and physiological deterioration (oxidative damage, tumor load), and a faster decline in fertility than populations from wetter regions. This parallel intraspecific divergence in life span and aging was not associated with divergence in early life history (rapid growth, maturation) or pace‐of‐life syndrome (high metabolic rates, active behavior). Variability across four study species suggests that a combination of different aging and life‐history traits conformed with or contradicted the predictions for each species. These findings demonstrate that variation in life span and functional decline among natural populations are linked, genetically underpinned, and can evolve relatively rapidly.     

Mortality rate, reproductive output, and trap response bias in populations of the blowfly Lucilia sericata

1. The ages of 877 females of the blowfly Lucilia sericata, collected from two farms in south-west England between May and September 1996, were determined using a combination of ovarian dissection and wing fray analysis. 2. Using survivorship analysis, the mortality rates over the entire field season were estimated to be 2.2 and 1.9% per day-degree at the two farms, respectively. These gave a mean life expectancy of 46 and 53 day-degrees, and a lifetime reproductive output of 130 and 172 eggs per female. 3. The mortality rate remained relatively constant over time, with one exception, the first sample of the season when no older flies were present, indicating that underlying changes in demography (emergence and senescence of generations) over the field season were not sufficient to affect the rates calculated by survivorship analysis. 4. The response of L. sericata to liver-baited traps was affected strongly by age and reproductive status, with gravid females and females in the early stages of ovarian development being most markedly over-represented relative to other age categories.