Years of potential life lost before age 65, by race, Hispanic origin, and sex--United States, 1986-1988.

A substantial proportion of mortality among young persons is preventable. National vital statistics were used to establish a baseline for the surveillance of rates of years of potential life lost before age 65 (YPLL < 65) in the United States. Rates of YPLL < 65 were calculated for 1986 through 1988 for leading causes of preventable death, by race, Hispanic origin, and sex. U.S. racial and ethnic populations differed widely in YPLL < 65. Among males, the rate (per 1,000 population < 65 years) of YPLL < 65 was highest for non-Hispanic blacks (140.0), followed by American Indians/Alaskan Natives (100.9), Hispanics (74.3), non-Hispanic whites (68.3), and Asians/Pacific Islanders (38.2). Among females, the rate was highest for non-Hispanic blacks (73.7), followed by American Indians/Alaskan Natives (52.0), non-Hispanic whites (35.7), Hispanics (32.9), and Asians/Pacific Islanders (23.2). For non-Hispanic blacks, the high rate of YPLL < 65 was due to increased rates for all causes of death considered, particularly homicide. The high rate for American Indians/Alaskan Natives was due principally to deaths from four causes: unintentional injuries, cirrhosis, suicide, and diabetes. Asians/Pacific Islanders had low rates for most causes of death. In setting health-care priorities and prevention strategies to reduce the large racial-ethnic gap in early deaths, it is essential to recognize the differences in causes of premature mortality among sex, racial, and ethnic populations. Periodic reassessment of YPLL < 65 among these groups provides a simple, timely, and representative means of conducting surveillance to measure the impact of intervention strategies on a national basis.     

道路交通伤及其他主要死因的减寿对比评估

目的对比评估交通伤及其他主要死因对期望寿命前死亡的影响。方法应用寿命损失年数(YPLL)及有关的期望寿命前死亡评估指标。结果2000年，辽宁省城市居民死亡中男性交通伤死亡仅占2．3％，但其所致的YPLL及潜在工作损失年数(WYPLL)在全死因所致YPLL及WYPLL中的构成比则分别升高至9．2％及7．8％。女性交通伤死亡仅占死因构成的1．1％，但其所致的YPLL及WYPLL在全死因所致YPLL及WYPLL中的构成比分别升高至3．8％及4．6％。脑血管病缺血性心脏病所致的YPLL及WYPLL在全死因所致的YPLL及WYPL中的构成比明显低于其死因构成比。男性人群中肿瘤所致的YPLL及WYPLL在全死因所致的YPLL及WYPLL中的构成比与其死因构成比接近，而女性人群中则高于死因构成比。每一人道路交通伤亡所致的YPLL／d及WYPLL／d均明显超过其他主要死因。每一人道路交通伤死亡所致的VYPLL／d为正值，而其他主要死因的VYPLL／d均为负值。结论交通伤对期望寿命前死亡的影响非常明显地大于脑血管病、缺血性心脏病及肿瘤等，已成为导致人群潜在寿命损失年数的主要原因之一。     

湖北省麻城市1974-2008年伤害死亡的长期趋势分析

目的 分析湖北省麻城市1974-2008年伤害死亡长期变化趋势、分布特点和疾病负担.方法 利用麻城市自1974年起建立的四级报告网络系统,对历年伤害死亡资料进行审核和整理,描述35年来伤害的死亡水平和主要死亡原因,并计算伤害导致的去死因期望寿命和潜在寿命损失年,以及伤害死亡和寿命损失占总死亡的比例.结果 麻城市35年伤害死亡率为62.64/10万至154.97/10万,其中男性为69.16/10万～163.86/10万,女性为55.34/10万～157.35/10万,男性高于女性.婴儿组的年平均伤害死亡率最高,达770.13/10万.伤害死亡率的地形分布以丘陵地区最高(37.03/10万),山区次之(33.66/10万),平原地区较低(31.43/10万).伤害死亡的前五位死因为自杀、淹溺、意外窒息、交通事故、意外跌落,共占伤害总死亡的84.26%,其中以自杀为最高,占伤害总死亡48.14%.伤害是儿童和青年的主要死因,在15～29岁年龄段伤害死亡占全死因比例最高,男性和女性分别为59.38%和62.26%.去伤害死亡期望寿命逐年提高,因伤害导致的潜在寿命损失年逐年下降.结论 麻城市伤害死亡率近10年虽有明显下降趋势,但仍处于较高水平;伤害主要死亡原因变化不大,各年段、年龄、性别、地形分布均以自杀为主,近年来交通事故的死亡率明显上升.     

Years of potential life lost among heroin addicts 33 years after treatment

OBJECTIVE: To examine premature mortality in terms of years of potential life lost (YPLL) among a cohort of long-term heroin addicts. METHOD: This longitudinal, prospective study followed a cohort of 581 male heroin addicts in California for more than 33 years. In the latest follow-up conducted in 1996/97, 282 subjects (48.5%) were confirmed as deceased by death certificates. YPLL before age 65 years was calculated by causes of death. Ethnic differences in YPLL were assessed among Whites, Hispanics, and African Americans. RESULTS: On average, addicts in this cohort lost 18.3 years (SD=10.7) of potential life before age 65. Of the total YPLL for the cohort, 22.3% of the years lost was due to heroin overdose, 14.0% due to chronic liver disease, and 10.2% to accidents. The total YPLL and YPLL by death cause in addict cohort were significantly higher than that of US population. The YPLL among African Americans was significantly lower than that among Whites or Hispanics. CONCLUSION: The YPLL among addicts was much higher than that in the national population; within the cohort, premature mortality was higher among Whites and Hispanics compared to African American addicts.     

伤害死亡对期望寿命影响趋势分析

目的以1985—2011年上海市嘉定区死亡资料为基础,分析伤害死亡长期变化趋势、分布特点及对期望寿命的影响。方法利用死因登记系统收集历年伤害死亡资料,描述27年来伤害死亡水平和主要死因,分析死亡率变化的时间趋势并估算年度变化百分比(APC),计算伤害导致的去死因期望寿命和潜在寿命损失年。结果1985—2011年嘉定区伤害平均死亡率为56.28/10万,占全死因的7.81%,居全死因顺位第4位;伤害是1~39岁年龄段人群的首位死因,前5位伤害死因依次为交通事故、意外跌落、自杀、淹溺以及机械性窒息;交通事故死亡率从1993年开始上升,2005年开始呈下降趋势;意外跌落死亡率从1994年开始呈上升趋势,APC上升为6.35%;因伤害导致的期望寿命损失年数男性平均为1.28岁,女性为1.13岁,因伤害导致的潜在寿命损失年(YPLL)平均为1 208.16人年/10万,占总死亡YPLL的20.13%,并呈逐年下降趋势。结论嘉定区伤害死亡率总体呈下降趋势,伤害仍是低年龄人群的主要死因,应重点关注意外跌落、交通事故的预防和控制。     

Potential gains in life expectancy or years of potential life lost: impact of competing risks of death

BACKGROUND: Measuring the impact of competing risks of death on society is important for setting public health policy and allocating resources. However, various indicators may result in inconsistent conclusions. The potential gains in life expectancy (PGLE) by elimination of deaths from HIV/AIDS, diseases of the heart and malignant neoplasms were compared to the years of potential life lost (YPLL) due to these causes in measuring the impact of premature death for the US population of working age (15-64 years). METHODS: The PGLE and the YPLL were computed from mortality reports (1987-1992) by race and gender group for deaths from HIV/AIDS, diseases of the heart and malignant neoplasms for the US population of working age. RESULTS: The YPLL overestimated the importance of premature deaths from HIV/AIDS compared to the PGLE. For the total US population and total US white population of working age, the YPLL were about 20-30% higher than the PGLE. However, the YPLL were about 20-30% lower than the PGLE for the US black population of working age. Furthermore the relative importance of the impact of death from various diseases may be interchanged by these two indicators. For example, for US black males of working age, the impact of deaths from HIV/AIDS by PGLE in 1992 was higher than that from malignant neoplasms and lower than that from diseases of the heart, but by using YPLL, the impact of premature deaths from HIV/AIDS was higher than that from both diseases of the heart and malignant neoplasms. CONCLUSIONS: The PGLE by elimination of deaths from diseases takes into account the competing risks on the population and it can be compared easily across populations. The YPLL is an index that does not take into account competing risks and it is also heavily influenced by the age structure and total population size. Although there are several standardization techniques proposed to improve the comparability of the YPLL across different populations, the YPLL fails to address the central issue of competing risks operating on the population. For this reason, we prefer the PGLE to the YPLL in measuring the impact of premature deaths on a population.     

A mortality analysis of Native American in New York State, 1980-86

This investigation examined the mortality experience of Native Americans in New York State, exclusive of New York City, between 1980 and 1986. Compared to the general population of New York State, exclusive of New York City, deaths among Native Americans occurred an average of nine years earlier. Among Native males, elevated risk of death was noted for tuberculosis, diabetes mellitus, pneumonia and cirrhosis. Native females demonstrated an excess of deaths due to diabetes mellitus and cirrhosis. Fewer than expected malignant neoplasm deaths occurred among both Native males and females. A deficit of deaths was observed for colon and lung cancer deaths among Native males and for colon and breast cancer deaths among Native females. While these results are generally in agreement with previous reports, this study did not identify an excess of deaths due to accident-related mortality. Findings from this study, while limited, do serve as crude indicators of the overall health status of Native Americans in New York State and may prove useful in the context of planning and evaluating future health care services among this population.     

长寿之乡如皋市如城镇居民死因及YPLL分析

目的了解长寿之乡如皋市如城镇居民死因和寿命损失特征,为制定卫生保健策略提供依据。方法分析居民各类死因的死亡率、构成、顺位及潜在减寿人年数等指标。结果全镇总死亡率为735.94/10万(标化411.57/10万),死因顺位前五位为恶性肿瘤、脑血管病、呼吸系统、心脏病、损伤和中毒;慢性非传染性疾病占总死亡的89.27%,比例很高;潜在寿命损失年最高为恶性肿瘤;恶性肿瘤中死亡率首位为肝癌,消化系肿瘤几乎都出现在前十位中,潜在寿命损失年首位亦为肝癌。结论人口老龄化后,恶性肿瘤死亡较心脑血管、呼吸系统疾病位次更为前移,慢性非传染性疾病成卫生保健重点。     

Years of potential life lost as the indicator of premature mortality in occupational medicine

Measurement of premature mortality is necessary to plan medical programs and to conduct effective medical activities. The purpose of this study was to compare the years of potential life lost (YPLL) with other mortality indices and to understand the usefulness and limitations of quantitative measurement for premature mortality. Data concerning death during employment were surveyed from 1979 to 1984. One thousand seven hundred twenty-five deaths were observed in 1,504,462 person-years in the study population. Proportionate mortality ratios indicated medical problems concerning malignant neoplasms and heart disease, but they could not identify the problems of suicide and traffic accidents occurring in the relatively younger group. YPLL by a constant end point at 60 years of age could rank these causes next below the major leading causes of death. Thus, YPLL might be a useful indicator of the problems concerning premature mortality in occupational medicine.     

中国人群1991～2000年伤害死亡的流行趋势和疾病负担

目的 了解1991～2000年中国人群伤害死亡的变化趋势、地区特点和疾病负担。方法使用全国疾病监测资料,经漏报调查结果进行调整,描述伤害的死亡水平和主要死亡原因,并计算伤害导致的平均潜在寿命损失年和潜在工作寿命损失年,以及伤害死亡、寿命损失和潜在工作寿命损失占总死亡的比例。结果 1991～2000年伤害死亡基本维持在恒定水平,经漏报率调整后10年平均伤害死亡率为66.56/10万,男性为81.41/10万,女性为51.17/10万。城市和农村人群的10年平均伤害死亡率分别为38.68/10万和74.63/10万。西部农村伤害的死亡率为81.02/10万,东、中、西部农村地区伤害死亡率之比为1:1.14:1.21。伤害是儿童和青年的主要死因,交通事故、自杀、淹溺、意外中毒、意外坠落是伤害的主要死因。自20世纪90年代以来,交通事故死亡率上升明显,至2000年已成为第一位死因。因伤害导致的潜在减寿年数是2132年/10万,导致的工作减寿年数为1587年/10万,分别占总死亡减寿年数的24.56％和26.51％。结论 伤害带来的疾病负担是严重的,由于“早死”,使伤害死亡带来更多的社会和经济损失,特别是交通伤害死亡率的上升应该引起更多重视,不同地区应针对本地区的重要伤害死亡谱和目标人群制订有效的控制策略。     

Disparities in deaths from stroke among persons aged <75 years--United States, 2002

Despite declines in deaths from stroke, stroke remained the third leading cause of death in the United States in 2002, and age-adjusted death rates for stroke remained higher among blacks than whites. In 1997, excess deaths from stroke occurred among persons aged <65 years in most racial/ethnic minority groups, compared with whites. A younger age distribution among Hispanics and other racial/ethnic groups compared with whites might partly explain the disproportionate burden in deaths at younger ages. To examine disparities in stroke mortality among persons aged <75 years, CDC assessed several characteristics of mortality at younger ages by using death certificate data for 2002. This report summarizes the results of that assessment. Overall, 11.9% of all stroke deaths in 2002 occurred among persons aged <65 years; the proportion of stroke decedents who were aged <65 years was higher among blacks, American Indians/Alaska Natives, and Asians/Pacific Islanders, compared with whites. In addition, the mean ages of stroke decedents were statistically significantly lower in these racial groups than among whites. Blacks had more than twice the age-specific death rates from stroke than whites aged <75 years. Approximately 3,400 excess stroke deaths would not have occurred among blacks in 2002 if blacks had had the same death rates for stroke as whites aged <65 years. Moreover, age-adjusted estimates of years of potential life lost (YPLL) before age 75 years from stroke were more than twice as high for blacks than for all other racial groups. Reducing premature death from stroke in these groups will require early prevention, detection, treatment, and control of risk factors for stroke in young and middle-aged adults.     

Social gradients in years of potential life lost in Ireland

BACKGROUND: The study of mortality differentials by class or socio-economic group is underdeveloped in Ireland in comparison to other countries. The work that has been done has used a standardized mortality ratio (SMR) methodology to measure deaths. There has been no previous work exploring the social gradient in years of potential life lost (YPLL) in Ireland. METHODS: The aim is to investigate socio-economic mortality differentials for men aged between 15 and 69 in Ireland, using YPLL as a measure of premature mortality. The design is a mortality trends study. The study is based on mortality data supplied by the Central Statistics Office in Ireland and population data taken from the Census for the years 1981 and 1991. The data covers all male deaths aged 15-69 in the years 1981 and 1991. Social position is measured by a 12-category socio-economic group (SEG) framework and by a more aggregate four-category occupational classification system. RESULTS: When age at death is taken into account through YPLL, injury and poisoning is a major cause of premature mortality in Ireland for all socio-economic groups. The results also show significant differentials in YPLL by 12-category SEG in Ireland. There was a widening of the social gap during the period 1981 to 1991 as measured by the YPLL ratio between lower manual/upper non-manual occupational groups. The use of YPLL as a measure of premature mortality highlights the importance of respiratory disease and injury and poisoning as the major sources of health inequality in 1981 and 1991. CONCLUSIONS: YPLL is an important indicator of general mortality and for monitoring mortality differentials by socio-economic group. Current health inequalities as measured by YPLL are unacceptably high in Ireland. A comprehensive government strategy to reduce inequalities in mortality is required, having the primary objective of improving the economic and social circumstances of people in the lower manual occupational category. There is also a need to develop measurable priorities and programmes for the reduction of premature mortality in the injury and poisoning category for all social groups, and especially for people in the lower manual group. This means action now to prevent future deaths from road accidents, accidents at work and suicides.     

我国9个市(县)艾滋病相关死亡回顾性分析

目的 了解艾滋病相关死亡历年变化情况及其对当地造成的寿命损失.方法 根据全国第3次死因调查方案和艾滋病死因同顾性分析的调查方案,采用州顾件调查的方法在云南省个旧市、云南省瑞丽市、云南省陇川县、广东省阳东县、广西壮族自治区鹿寨县、河南省尉氏县、河南省柘城县、湖北省浠水县和河北省固安县6省9市(县)进行死亡名单摸底、人口资料收集、入户调查和死因推断,回顾性分析艾滋病死亡构成及其寿命损失.结果 在6省9市(县)共调查死亡人数118 719例,粗死亡率为5.83%,其中艾滋病相关死亡2002例,占1.67%.艾滋病平均死亡年龄为38.03岁,明显早于非艾滋病死亡的平均年龄(63.10岁),其平均减寿年数为33.80年,人均工作寿命损失为20.50年,其造成的平均潜在寿命损失在所有死因中排第2位.结论 艾滋病在全死因构成中占有一定的比例,在部分高发地区,其死因构成超过10%以上,并已造成较为严重的潜在寿命和潜在工作寿命损失.     

2008—2019年无锡市跌倒死亡的疾病负担及对期望寿命的影响分析

目的 分析江苏省无锡市2008—2019年跌倒死亡导致的疾病负担及对期望寿命的影响,为制定干预措施提供依据。方法 利用2008—2019年无锡市全人群死因监测数据,计算跌倒死亡率和早死所致寿命损失年(years of life lost,YLL),以平均年度变化百分比(average annual percent change, AAPC)分析变化趋势及对期望寿命增量的贡献。结果 2008—2019年无锡市居民跌倒粗死亡率AAPC为7.0%(95%CI:4.8～9.4)(P<0.05)和标化死亡率AAPC为3.7%(95%CI:1.4～6.0)均呈上升趋势(P<0.05)。2008—2019年因跌倒死亡中,女性占比达到57.62%,略高于男性,且60岁及以上老年人占比达到89.98%。2008—2019年因跌倒死亡导致的期望寿命平均下降了0.11岁(6.43%),且对女性影响大于男性。2008—2019年全人群和60岁及以上老年人因跌倒死亡导致的YLL率均呈上升趋势,AAPC分别为3.3%(95%CI:1.2～5.5)(P<0.05)和4.5%(95%CI:2.0～7...     

The contribution of specific causes of death to sex differences in mortality

OBJECTIVE: Men have higher mortality rates than women for most causes of death. This study was conducted to determine the contribution of specific causes of death to the sex difference in years of potential life lost (YPLL). METHODS: The authors examined data from the National Health Interview Survey with linked mortality data through 1997. Using survival analysis estimates, a stochastic simulation model to simulate death events for cohorts of white, African American, and Latino adults was created. RESULTS: YPLL from all causes were greater among men than women. Homicide, motor vehicle accidents, and suicide accounted for 33% of YPLL sex difference among whites, 36% among African Americans, and 52% among Latinos. For all three racial/ethnic groups, cardiovascular disease (principally ischemic heart disease) was the second largest contributor to the sex difference in YPLL (29% among whites, 23% among African Americans, and 25% among Latinos). Lung cancer was also important among whites and African Americans, accounting for 15% and 17% of the sex difference in YPLL from all causes, respectively. CONCLUSIONS: Ischemic heart disease, lung cancer, and traumatic deaths account for as much as three-quarters of the excess YPLL among men, suggesting that a few modifiable behaviors such as the use of tobacco, alcohol.     

武汉市2009年居民伤害死亡状况及疾病负担分析

目的分析武汉市2009年伤害死亡的流行特征和疾病负担,为制定伤害预防控制策略和措施提供科学依据。方法采用粗死亡率、标化死亡率、潜在寿命损失年、标化潜在寿命损失年、潜在工作损失年等指标对武汉市2009年居民病伤死亡监测资料伤害死亡数据进行分析。结果 2009年武汉市伤害的粗死亡率为45.50/10万,标化率为33.01/10万,男性（54.77/10万）明显高于女性（35.77/10万）,农村（49.66/10万）明显高于城市（42.63/10万）,伤害死亡的主要原因依次是交通事故、溺水、跌落、自杀、意外中毒和他杀,0-岁人群伤害的主要死因是溺水,15-岁人群则是交通伤害,65岁及以上人群则以跌落为主,其次为交通事故和自杀。因伤害导致的YPLL,SYPLL和WYPLL分别为73 470年、84 734年和50 073年,分别占全死因的24.01%、30.36%和31.62%,远远高于伤害占全死因的比例7.46%。结论伤害是导致＂早死＂和寿命损失的重要疾病负担,由于伤害死亡带来的社会和经济损失应引起相关卫生部门更多的重视,根据伤害的死亡谱和危险人群制定有效的防控措施,最大限度的减少伤害所致的死亡与残疾。     

2013 - 2018年安徽省伤害死亡变化趋势及潜在寿命损失分析

目的 了解安徽省居民伤害死亡特征和潜在寿命损失情况,为制定防控措施提供依据。方法 利用2013 - 2018年安徽省全国死因监测点数据,用SPSS 20.0和Excel 2007软件分析伤害死亡率及其年度变化百分比（APC）、潜在减寿年数（PYLL）、减寿率（PYLLR）、平均减寿年数（AYLL）等指标。结果 2013 - 2018 年安徽省伤害标化死亡率47.40/10万,呈逐年下降趋势（t = - 6.77,P ＜0.01）。伤害死亡率男性＞女性,农村＞城市,皖北＞皖中＞皖南。伤害是全人群第5位死因（占7.94%）,是0～44岁组首位死因。伤害死因前5位依次是交通事故、自杀、意外跌落、溺水和意外中毒。溺水、交通事故、自杀分别是0～14岁、15～64岁、≥65岁组首位伤害死因。伤害PYLLR为10.73‰,AYLL为26.53年,居全死因第1位。其中交通事故PYLL最高,溺水AYLL最高。结论 安徽省伤害死亡疾病负担较重,应根据不同人群的伤害死亡特征制定相应的防制策略。     

金山区居民伤害死亡原因及控制策略

[目的 ]　了解伤害死亡对各年龄组人群的危害程度及变化趋势 ,探讨伤害预防控制的对策。[方法 ]　按国际疾病分类第九版 (ICD -9)进行死因分类 ,统计分析伤害死亡率、潜在减寿年数 (YPLL)、标化YPLL、YPLL标化率。[结果 ]　金山区居民伤害死亡率仅次于呼吸系统病、循环系统病和肿瘤 ,居第 4位 ,占全区居民死亡人数的 7.0 3 %～ 8.77% ,前 4位伤害死因依次为交通事故 ( 3 4 .2 1% )、自杀 ( 2 0 .10 % )、意外跌落 ( 14 .18% )和溺水 ( 13 .75 % )。全人群非故意伤害和故意伤害标化死亡率分别为 40 .71/10万、9.95 /10万。经YPLL分析 ,伤害死亡死因位次由原来的第 4位升至首位 ,1～ 14岁儿童潜在寿命损失为 64 .61年 /千人 ,居各年龄组之首。 [结论 ]　伤害死亡对居民的危害和潜在寿命损失不容忽视 ,应当建立伤害报告信息管理系统 ,采取以社区为基础的干预对策控制伤害发生。     

意外伤害的死亡率和潜在寿命损失年数的比较分析

应用标化死亡率和潜在寿命损失年数(YPLL)对广州市1988~1994年的意外伤害进行分析,结果显示意外伤害在死因构成中居第四位,但在YPLL率的排位中则跃居第二位;男女性别比为1.69:1,男性的意外伤害多发生在青、中年,女性则以青、老年多见。随着寿命年数损失的增加,潜在工作损失年数(WYPLL)和潜在价值损失年数(VYPLL)也相应加大。与标化死亡率相比较的结果,揭示YPLL能更合理地反映意外伤害死亡对低年龄层人群所造成的实质性损失。     

新疆生产建设兵团1997～1999年居民期望寿命调查分析

目的：分析新疆生产建设兵团20世纪末的居民期望寿命和与寿命有关的指标。方法：采用分层胡机抽样方法，获得期望寿命，死亡率，死因顺位，去死因寿命，潜在减寿年数（YPLL）及人口长寿水平等指标，并对各项指标进行简要分析。结果：新疆生产兵团（兵团）1997－1999年期望寿命为75．61岁，男为72．73岁，女性为80．02岁；农牧团场的期望寿命为73．97岁，相对较低；经济水平高的地区期望寿命较高较高；北疆地区期望寿命高于南疆和东疆，年平均粗死亡率为5．17‰（标化死亡率为4．53‰）。主要死因顺位为：恶性肿瘤、脑血管病，呼吸系统疾病，心脏病，损伤与中毒，传染病与寄生虫病以及围产期情况。7种死因中，去除呼吸系统疾病和围产期情况寿命增幅较明显。主要死因的潜在减行率和标准化潜在减寿（SYPLL）率顺位的第1位均为意外死亡。经济水平较高地区长寿水平也较高，结论：兵团人均期望寿命水平较高，但不同地区相差较大，为全面提高居民健康水平，既要加强自然环境的治理和扶贫力度。也要重视呼吸系统（尤其是婴儿）、老年慢性病的防治和提高围期产期保健质量，进一步改善社会保障环境，降低损伤中毒的发生率。