Has the relation between income inequality and life expectancy disappeared? Evidence from Italy and top industrialised countries

OBJECTIVE: To investigate the relation between income inequality and life expectancy in Italy and across wealthy nations. DESIGN AND SETTING: Measure correlation between income inequality and life expectancy at birth within Italy and across the top 21 wealthy countries. Pearson correlation coefficients were calculated to study these relations. Multivariate linear regression was used to measure the association between income inequality and life expectancy at birth adjusting for per capita income, education, and/or per capita gross domestic product. DATA SOURCES: Data on the Gini coefficient (income inequality), life expectancy at birth, per capita income, and educational attainment for Italy came from the surveys on Italian household on income and wealth 1995-2000 and the National Institute of Statistics information system. Data for industrialised nations were taken from the United Nations Development Program's human development indicators database 2003. RESULTS: In Italy, income inequality (beta = -0.433; p<0.001) and educational attainment (beta = 0.306; p<0.001) were independently associated with life expectancy, but per capita income was not (beta = 0.121; p>0.05). In cross national analyses, income inequality had a strong negative correlation with life expectancy at birth (r = -0.864; p<0.001). CONCLUSIONS: In Italy, a country where health care and education are universally available, and with a strong social safety net, income inequality had an independent and more powerful effect on life expectancy at birth than did per capita income and educational attainment. Italy had a moderately high degree of income inequality and an average life expectancy compared with other wealthy countries. The cross national analyses showed that the relation between income inequality and population health has not disappeared.     

Toward measuring the impact of ecological disintegrity on human health

Ecological integrity refers to the ability of environmental life-support systems to sustain themselves in the face of human-induced impacts. We used a correlational, aggregate-data study design to explore whether life expectancy, as a general measure of population health, is linked to large-scale declines in ecological integrity. Most of the data were obtained from World Resources Institute publications. Selected surrogate measures of ecological integrity and gross domestic product (GDP) per capita (as a socioeconomic confounder) were modeled, for the first time, using linear regression techniques with life expectancy as the health outcome. We found a modest relation between ecological integrity and life expectancy, but the direction of the association was inconsistent. When GDP per capita was controlled, the relation between ecological integrity and life expectancy was lost. GDP per capita was the overwhelming predictor of health. Any relation between ecological integrity and health may be mediated by socioeconomic factors. The effect of declines in ecological integrity may be cushioned by the exploitation of ecological capital, preventing a direct association between measures of exposure and outcome. In addition, life expectancy may be too insensitive a measure of health impacts related to ecological decline, and more sensitive measures may need to be developed.     

"Social capital," GNP per capita, relative income, and health: an ecological study of 23 countries.

The effects of social capital, income inequality, and absolute per capita income were investigated in an ecological analysis of 23 rich and poor countries. Trust was chosen as an indicator of social capital, and GNP (gross national product) per capita and Gini index measured absolute and relative income, respectively. These independent variables were analyzed in a linear regression model with the dependent variables adult mortality rate (25-64 years), life expectancy, and infant mortality rate (IMR). Separate analyses were performed for poor and rich countries as well as all countries combined. Social capital (trust) showed no significant association with the three health outcomes. A particularly strong relationship was found between Gini index and IMR for rich countries, and GNP per capita and life expectancy for all countries. In the group of poor countries, GNP per capita and Gini index in the same model were associated with IMR. The results contradict the suggested impact of social capital on health, and instead support the notion that economic factors such as absolute income and relative income distribution are of importance.     

A crossectional country group study of three health level outcomes and four potential causes.

A crossectional study of four country groups segmented by per capita income of the majority of the world's countries was made to evaluate the relationship between health level outcomes and potential causes which may impact on the health level outcomes. The health level outcomes consist of life expectancy at birth, infant mortality rate and child mortality rate. The potential causes consist of secondary school children per 100 in school age group, daily calory supply per capita, population per physician and population per nurse. For the two lower income country groups the two important determinants of life expectancy were daily calory supply per capita and secondary school children per 100 in school age group. For the upper middle income the country group the important positive determinant of life expectancy was population per nurse and for the upper income country group the important negative determinant of life expectancy was daily calory supply per capita. Infant and child mortality rates were associated with secondary school children per 100 in school age group and population per physician or population per nurse for the two lower income country groups. For the upper middle income country group population per nurse or population per physician was supplemented by daily calory supply per capita for both infant and child mortality. For the upper income country group only infant mortality had statistically significant determinants. They were daily calory supply per capita and secondary school children per 100 in school age groups.     

Is wealthier always healthier? The impact of national income level,inequality, and poverty on public health in Latin America

Despite findings indicating that both national income level and income inequality are each determinants of public health, few have studied how national income level, poverty and inequality interact with each other to influence public health outcomes. We analyzed the relationship between gross domestic product (GDP) per capita in purchasing power parity, extreme poverty rates, the gini coefficient for personal income and three common measures of public health: life expectancy, infant mortality rates, and tuberculosis (TB) mortality rates. Introducing poverty and inequality as modifying factors, we then assessed whether the relationship between GDP and health differed during times of increasing, decreasing, and decreasing or constant poverty and inequality. Data were taken from twenty-two Latin American countries from 1960 to 2007 from the December 2008 World Bank World Development Indicators, World Health Organization Global Tuberculosis Database 2008, and the Socio-Economic Database for Latin America and the Caribbean. Consistent with previous studies, we found increases in GDP have a sizable positive impact on population health. However, the strength of the relationship is powerfully influenced by changing levels of poverty and inequality. When poverty was increasing, greater GDP had no significant effect on life expectancy or TB mortality, and only led to a small reduction in infant mortality rates. When inequality was rising, greater GDP had only a modest effect on life expectancy and infant mortality rates, and no effect on TB mortality rates. In sharp contrast, during times of decreasing or constant poverty and inequality, there was a very strong relationship between increasing GDP and higher life expectancy and lower TB and infant mortality rates. Finally, inequality and poverty were found to exert independent, substantial effects on the relationship between national income level and health. Wealthier is indeed healthier, but how much healthier depends on how increases in wealth are distributed.     

Health status during the transition in Central and Eastern Europe: development in reverse?

This paper reports on a study of the cross-national trends in health status during the economic transition and associated health sector reforms in Central and Eastern Europe (CEE). The central premise is that before long-run gains in health status are realized, the transition towards a market economy and adoption of democratic forms of government should lead to short-run deterioration as a result of: (i) reduction in real income and widening income disparities; (ii) stress and stress-related behaviour; (iii) lax regulation of environmental and occupational risks; and (iv) breakdown in basic health services. Analysis focused on three broad indicators of health status: life expectancy at birth, infant mortality rate and the probability of dying between the ages of 15 and 65 years, shown by the notation '50q15'. The study revealed significant new information about health status and the health sector which could not have been obtained without a proper cross-national study. Infant mortality rates in former socialist economies (FSE) follow the global trend, declining as per capita income rises. However, rates are lower than would be predicted given their income levels. Despite declining infant mortality, life expectancy at birth in the former socialist economies decreases as per capita income rises, in marked contrast to global trends. This is because rising income level is associated with greater probability of death between the ages of 15 and 65: the wealthier the society, the less healthy is its population, particularly for its males. Causes of death in the FSE follow global trends: higher death rates due to infectious and parasitic diseases in poorer countries, and higher death rates due to chronic diseases in wealthier countries. However, age-standardized death rates for chronic diseases generally associated with unhealthy lifestyles and environmental risk factors are very high when compared with wealthier established market economies (EME). Policies and procedures which alter the effectiveness of health services have had a demonstrable but mixed impact on health status during the early phase of transition. Effective preventive health strategies must be formulated and implemented to reverse the adverse trends observed in Central and Eastern Europe.     

Variations in infant mortality rates among municipalities in the state of Ceará, Northeast Brazil: an ecological analysis.

BACKGROUND: Infant mortality rates vary substantially among municipalities in the State of Ceará, from 14 to 193 per 1000 live births. Identification of the determinants of these differences can be of particular importance to infant health policy and programmes in Brazil where local governments play a pivotal role in providing primary health care. METHODS: Ecological study across 140 municipalities in the State of Ceará, Brazil. RESULTS: To determine the interrelationships between potential predictors of infant mortality, we classified 11 variables into proximate determinants (adequate weight gain and exclusively breastfeeding), health services variables (prenatal care up-to-date, participation in growth monitoring, immunization up-to-date, and decentralization of health services), and socioeconomic factors (female literacy rate, household income, adequate water supply, adequate sanitation, and per capita gross municipality product), and included the variables in each group simultaneously in linear regression models. In these analyses, only one of the proximate determinants (exclusively breastfeeding (inversely), R2 = 9.3) and one of the health services variables (prenatal care up-to-date (inversely), R2 = 22.8) remained significantly associated with infant mortality. In contrast, female literacy rate (inversely), household income (directly) and per capita GMP (inversely) were independently associated with the infant mortality rate (for the model including the three variables R2 = 25.2). Finally, we considered simultaneously the variables from each group, and selected a model that explained 41% of the variation in infant mortality rates between municipalities. The paradoxical direct association between household income and infant mortality was present only in models including female illiteracy rate, and suggests that among these municipalities, increases in income unaccompanied by improvements in female education may not substantially reduce infant mortality. The lack of independent associations between inadequate sanitation and infant mortality rates may be due to the uniformly poor level of this indicator across municipalities and provides no evidence against its critical role in child survival. CONCLUSIONS: These results suggest that promotion of exclusive breastfeeding and increased prenatal care utilization, as well as investments in female education would have substantial positive effects in further reducing infant mortality rates in the State of Ceará.     

Societal characteristics and health in the former communist countries of Central and Eastern Europe and the former Soviet Union: a multilevel analysis

OBJECTIVES: To examine whether, in former communist countries that have undergone profound social and economic transformation, health status is associated with income inequality and other societal characteristics, and whether this represents something more than the association of health status with individual socioeconomic circumstances. DESIGN: Multilevel analysis of cross-sectional data. SETTING: 13 Countries from Central and Eastern Europe and the former Soviet Union. PARTICIPANTS: Population samples aged 18+ years (a total of 15 331 respondents). MEAN OUTCOME MEASURES: Poor self-rated health. RESULTS: There were marked differences among participating countries in rates of poor health (a greater than twofold difference between the countries with the highest and lowest rates of poor health), gross domestic product per capita adjusted for purchasing power parity (a greater than threefold difference), the Gini coefficient of income inequality (twofold difference), corruption index (twofold difference) and homicide rates (20-fold difference). Ecologically, the age- and sex-standardised prevalence of poor self-rated health correlated strongly with life expectancy at age 15 (r = -0.73). In multilevel analyses, societal (country-level) measures of income inequality were not associated with poor health. Corruption and gross domestic product per capita were associated with poor health after controlling for individuals' socioeconomic circumstances (education, household income, marital status and ownership of household items); the odds ratios were 1.15 (95% confidence interval 1.03 to 1.29) per 1 unit (on a 10-point scale) increase in the corruption index and 0.79 (95% confidence interval 0.68 to 0.93) per $5000 increase in gross domestic product per capita. The effects of gross domestic product and corruption were virtually identical in people whose household income was below and above the median. CONCLUSION: Societal measures of prosperity and corruption, but not income inequalities, were associated with health independently of individual-level socioeconomic characteristics. The finding that these effects were similar in persons with lower and higher income suggests that these factors do not operate exclusively through poverty.     

The relationship between health and GDP in OECD countries in the very long run

This paper uses Johansen multivariate cointegration analysis to examine the relationship between health and GDP for 13 OECD countries over the last two centuries, for periods ranging from 1820–2001 to 1921–2001. A similar, long run, cointegrating relationship between life expectancy and both total GDP and GDP per capita was found for all the countries estimated. The relationships have a significant influence on both total GDP and GPD per capita in most of the countries estimated, with 1% increase in life expectancy resulting in an average 6% increase in total GDP in the long run, and 5% increase in GDP per capita. Total GDP and GDP per capita also have a significant influence on life expectancy for most countries. There is no evidence of changes in the relationships for any country over the periods estimated, indicating that shifts in the major causes of illness and death over time do not appear to have influenced the link between health and economic growth. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of the impact of the Family Health Program on infant mortality in Brazil, 1990-2002

OBJECTIVE: To use publicly available secondary data to assess the impact of Brazil's Family Health Program on state level infant mortality rates (IMR) during the 1990s. DESIGN: Longitudinal ecological analysis using panel data from secondary sources. Analyses controlled for state level measures of access to clean water and sanitation, average income, women's literacy and fertility, physicians and nurses per 10,000 population, and hospital beds per 1,000 population. Additional analyses controlled for immunisation coverage and tested interactions between Family Health Program and proportionate mortality from diarrhoea and acute respiratory infections. SETTING: 13 years (1990-2002) of data from 27 Brazilian states. MAIN RESULTS: From 1990 to 2002 IMR declined from 49.7 to 28.9 per 1,000 live births. During the same period average Family Health Program coverage increased from 0% to 36%. A 10% increase in Family Health Program coverage was associated with a 4.5% decrease in IMR, controlling for all other health determinants (p<0.01). Access to clean water and hospital beds per 1,000 were negatively associated with IMR, while female illiteracy, fertility rates, and mean income were positively associated with IMR. Examination of interactions between Family Health Program coverage and diarrhoea deaths suggests the programme may reduce IMR at least partly through reductions in diarrhoea deaths. Interactions with deaths from acute respiratory infections were ambiguous. CONCLUSIONS: The Family Health Program is associated with reduced IMR, suggesting it is an important, although not unique, contributor to declining infant mortality in Brazil. Existing secondary datasets provide an important tool for evaluation of the effectiveness of health services in Brazil.     

Linkages between biodiversity loss and human health: a global indicator analysis

The association between health and biodiversity loss was explored by means of regression analysis on a global scale, with control for confounding by socio-economic developments. For this we selected indicators of human health (life expectancy, disability adjusted life expectancy, infant mortality rate and percentage low-birthweight babies), biodiversity (percentage threatened species, current forest as a percentage of original forest, percentage of land highly disturbed by man) and socio-economic development (health expenditure as percentage of GNP, percentage one-year olds immunized, illiteracy rate, GNP per capita and development grade) on a country level. After controlling for relevant socio-economic confounders, both current forest as a percentage of original forest and the percentage of land highly disturbed by human activities had no relationship with one of the health indicators. The logarithm of the percentage threatened species, showed a positive association with life expectancy and disability adjusted life expectancy. The present study was not able to provide any empirical proof of a negative association between loss of biodiversity and human health at the global scale. This does not mean, however, that no such relationship exists, because there may be several reasons for our findings, like possible non-linearity of the relationship, lack of suitable indicators, non-randomness in the sample of countries and the limitations of regression analysis in proving causality.     

Correlation between national income, HIV/AIDS and political status and mortalities in African countries

OBJECTIVES: To investigate associations between mortalities in African countries and problems that emerged in Africa in the 1990s (reduction of national income, HIV/AIDS and political instability) by adjusting for the influences of development, sanitation and education. METHODS: We compiled country-level indicators of mortalities, national net income (the reduction of national income by the debt), infection rate of HIV/AIDS, political instability, demography, education, sanitation and infrastructure, from 1990 to 2000 of all African countries (n=53). To extract major factors from indicators of the latter four categories, we carried out principal component analysis. We used multiple regression analysis to examine the associations between mortality indicators and national net income per capita, infection rate of HIV/AIDS, and political instability by adjusting the influence of other possible mortality determinants. RESULTS: Mean of infant mortality per 1000 live births (IMR); maternal mortality per 100,000 live birth (MMR); adult female mortality per 1000 population (AMRF); adult male mortality per 1000 population (AMRM); and life expectancy at birth (LE) in 2000 were 83, 733, 381, 435, and 51, respectively. Three factors were identified as major influences on development: education, sanitation and infrastructure. National net income per capita showed independent negative associations with MMR and AMRF, and a positive association with LE. Infection rate of HIV/AIDS was independently positively associated with AMRM and AMRF, and negatively associated with LE in 2000. Political instability score was independently positively associated with MMR. CONCLUSIONS: National net income per capita, HIV/AIDS and political status were predictors of mortality indicators in African countries. This study provided evidence for supporting health policies that take economic and political stability into account.     

Health care expenditure and life expectancy in Australia: how well do we perform?

Abstract: The Australian health care system consists of mixed public and private financing underpinned by Medicare, a universal government-run insurance scheme paid through taxation (and levy) on income. Australia has improved its ranking for life expectancy (at birth) since 1960, and in 1990 ranked ninth and seventh of 24 countries for females and males respectively; this is ahead of the United States and United Kingdom, and approximately equal to Canada. Australian hospital bed supply and utilisation are average, after deletion of day-only cases. The proportion of gross domestic product (GDP) spent on health, in relation to GDP per capita (adjusted for purchasing power), in Australia in 1990 was average, and the prices for health care from 1975 to 1990 did not increase when adjusted for inflation. Although 68 per cent of health expenditure emanates from public sources in Australia, this is lower than in the majority of European countries and Canada. Some countries are doing poorly (such as the United States, with lower than average life expectancy and higher than predicted health expenditure) and some countries are doing well (with higher than average life expectancy and lower than predicted health expenditure; for example, Japan). Australia has higher than average life expectancy and only slightly higher than predicted health expenditure per capita. Although the Australian system could be improved, there are no indications that radical changes are required. The relatively high life expectancy in Australia can be attributed to favourable social and economic conditions, successful public health programs, and the availability of universal quality health care.     

Inter-state disparities in health care and financial burden on the poor in India

Over five decades of independence, India has made rapid strides in various sectors. However, its performance in social sectors and particularly the healthcare sector has not been too rosy. Being the State's responsibility the healthcare has traditionally been influenced by individual State's budgetary allocation. Consequently inter-state disparity in availability and utilization of health services and health manpower are distinctly marked. This has implications for achievement of Health for All for the nation as a whole. Keeping in view the significance of studying inter-state variations in healthcare, this study focuses on the performance of healthcare sector in 15 major States in India. This is attempted through a comparative analysis of various parameters depicting availability of health services, their utilization and health outcomes. Our analysis depicts the prevalence of considerable inequity favoring high income group of States. In terms of healthcare resources, for instance, it indicates that the high income States hold a superior position in terms of: per capita government expenditure on medical and public health, total number of hospitals and dispensaries, per capita availability of beds in hospitals and dispensaries and health manpower in rural and urban areas. These parameters of availability have an impact on utilization levels and health outcomes in these States. A comparative profile of high and low income States as well as middle and low income States, both in rural and urban areas, reaffirms a greater financial burden in availing treatment at OPD and inpatient in low income States. In line with the higher financial burden and low per capita health expenditure, the health outcome indicators also depict a disconcerting situation in regard to low income States. These States are marked by lower life expectancy and higher incidence of diseases as well as high mortality rates. In this regard, demand as well as supply side constraints are observed which restrain the optimum utilization of existing health services. Among the low income States the main constraints on the demand side include illiteracy, malnutrition, and lack of infrastructure in accessing the facilities. Certain state specific supply side factors add significantly to under-utilization in low income States. In some of the States, however, corrective actions have been initiated to overcome the problem of the quality and low utilization of health facilities. In due course of time, it is likely that proper implementation of these measures may result in improved utilization level of existing health services, which may be useful to improve health status indicators. Nonetheless, overcoming the current levels of regional disparities in healthcare across three income groups of States may also require additional resources. The latter could be mobilized through assistance of donor agencies and appropriate mix of social and private insurance. Ultimately mitigating the problem of regional disparities in healthcare and protecting the poor and vulnerable from financial burden may require establishing and maintaining proper linkages between socio-economic development and healthcare planning.     

Socioeconomic determinants of infant mortality: a worldwide study of 152 low-, middle-, and high-income countries

BACKGROUND: To reach the Millennium Development Goals for health, influential international bodies advocate for more resources to be directed to the health sector, in particular medical treatment. Yet, health has many determinants beyond the health sector that are less evident than proximate predictors. AIM: To assess the relative importance of major socioeconomic determinants of population health, measured as infant mortality rate (IMR), at country level. METHODS: National-level data from 152 countries based on World Development Indicators 2003 were used for multivariate linear regression analyses of five socioeconomic predictors of IMR: public spending on health, GNI/capita, poverty rate, income equality (Gini index), and young female illiteracy rate. Analyses were performed on a global level and stratified for low-, middle-, and high-income countries. RESULTS: In order of importance, GNI/capita, young female illiteracy, and income equality predicted 92% of the variation in national IMR whereas public spending on health and poverty rate were non-significant determinants when adjusted for confounding. In low-income countries, female illiteracy was more important than GNI/capita. Income equality (Gini index) was an independent predictor of IMR in middle-income countries only. In high-income countries none of these predictors was significant. CONCLUSIONS: The relative importance of major health determinants varies between income levels, thus extrapolating health policies from high- to low-income countries is problematic. Since the size, per se, of public health spending does not independently predict health outcomes, functioning health systems are necessary to make health investments efficient. Potential health gains from improved female education and economic growth should be considered in low- and middle-income countries.     

Amenable mortality as a performance indicator of Italian health-care services

ABSTRACT: BACKGROUND: Mortality amenable to health-care services ('amenable mortality') has been defined as "premature deaths that should not occur in the presence of timely and effective health care" and as "conditions for which effective clinical interventions exist." We analyzed the regional variability in health-care services using amenable mortality as a performance indicator. Convergent validity was examined against other indicators, such as health expenditure, GDP per capita, life expectancy at birth, disability-free life expectancy at age 15, number of diagnostic and laboratory tests per 1,000 inhabitants, and the prevalence of cancer and cardiovascular diseases. METHODS: Amenable mortality rate was calculated as the average annual number of deaths in the population aged 0--74 years per 100,000 inhabitants, and it was then stratified by gender and region. Data were drawn from national mortality statistics for the period 2006--08. RESULTS: During the study period (2006--08), the age-standardized death rate (SDR) amenable to health-care services in Italy was 62.6 per 100,000 inhabitants: 66.0 per 100,000 for males and 59.1 per 100,000 for females. Significant regional variations ranged from 54.1 per 100,000 inhabitants in Alto Adige to 76.3 per 100,000 in Campania. Regional variability in SDR was examined separately for male and females. The variability proved to be statistically significant for both males and females (males: Q-test = 638.5, p < 0.001; females: Q-test = 700.1, p < 0.001). However, among men, we found a clear-cut divide in SDR values between Central and Southern Italy; among women, this divide was less pronounced. Amenable mortality was negatively correlated with life expectancy at birth for both genders (male: r = -0.64, p = 0.002; female: r = -0.88, p <0.001) and with disability-free life expectancy at age 15 (male: r = -0.70, p <0.001; female: r = -0.67, p <0.001). Amenable mortality displayed a statistically significant negative relationship with GDP per capita, the quantity of diagnostic and laboratory tests per 1,000 inhabitants, and the prevalence of cancer. CONCLUSIONS: Amenable mortality shows a wide variation across Italian regions and an inverse relationship with life expectancy and GDP per capita, as expected.     

Socioeconomic circumstances and health among the brazilian elderly: a study using data from a National Household Survey

The influence of socioeconomic circumstances on senior citizens' health is still controversial. We used data from the 1998 Brazilian National Household Survey (PNAD 1998) to examine this influence. A representative sample of the Brazilian population aged > or = 65 years (n = 19,068) were included in the study. The characteristics of those in the lower quintile of per capita household income were compared with those with higher income (< 0.67 vs > or = 0.67 the Brazilian minimum wage). The lower income group presented worse health conditions (self-rated health, inability to perform routine activities due to a health problem, bedridden conditions, and a report of any disease), and worse physical functioning (level of difficulty in performing selected physical activities), and less frequent use of medical and dental services. These results do not confirm observations, in some developed countries, of a lack of association between socioeconomic status and health among the elderly. On the contrary, according to our results, in Brazil even small differences in income are sufficiently sensitive to identify older adults with worse health conditions and limited access to health services.     

我国医疗卫生支出对期望寿命影响的因果分析研究

目的 探究我国医疗卫生支出对期望寿命的影响及其之间的因果关系。方法 利用世界银行给出的中国人口数据,使用R语言对该数据进行协整检验、格兰杰因果关系检验,分析我国医疗卫生支出与期望寿命之间的因果关系。结果 本研究发现我国期望寿命与公共卫生医疗支出存在正向的长期均衡关系（回归系数=0.490,t值=19.10,P<0.001）,与人口自然增长率（回归系数=-0.035,t值=-11.38,P<0.001）、人均医疗卫生支出（回归系数=-5.01,t值=-17.91,P<0.001）则存在反向的长期均衡关系。人口自然增长率（P=0.007）、公共卫生医疗支出（P<0.001）和人均医疗卫生支出（P<0.001）均是期望寿命的原因,但不存在互为因果关系。结论 医疗卫生支出的提高推动了期望寿命的提高,而人口自然增长率和人均医疗卫生支出的对期望寿命提高作用不大。