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Recent Trends in Mortality Due to Chronic Obstructive Pulmonary Disease (COPD) in Mexico, 1980–2002
Archives of Medical Research 36 (2005) 65–69
ORIGINAL ARTICLE
Recent Trends in Mortality Due to Chronic Obstructive Pulmonary Disease (COPD) in Mexico, 1980–2002 Victor Jose´ Tovar Guzma´n, Francisco Javier Lo´pez Antun˜ano and Norma Rodrı´guez Salgado Departamento de Investigacio´n en Tabaco, Centro de Investigacio´n en Salud Poblacional, Instituto Nacional de Salud Pu´blica, Cuernavaca, Morelos, Me´xico Received for publication May 31, 2004; accepted October 18, 2004 (04/001).
Background. Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. Changes in classification have a major impact on reported mortality rates. Methods. Between 1980 and 2002, 230,463 COPD cases were studied (age group 35⫺94 years); 134,579 men; 95,884 women. Results. The crude mortality rate varied from 37 (1980) to 61 per 100,000 men (2002), (increase: 65%). The crude mortality rate for females increased from 27 (1980) to 43 deaths per 100,000 women (2002), (increase: 56%). The trends of the absolute values by birth year and age groups are higher as age increases. As age of death comes down and the birth cohort increases, the absolute values decrease. The Mexican states located in the northern and central areas present a higher risk for dying. There is an increment coefficient of 93 cases per increment year in males (age group 35–74), and 61 cases per increment year in females (age group 35–74 years). For the age group 35–94 years, the annual increase for males is 288 cases. These results were statistically significant, and the regression model was validated by residual analysis. Conclusions. The oldest cohorts of the studied population showed the highest COPD mortality absolute values. The geographic risk of dying from COPD is concentrated in two regions: a) the three Mexican states of higher economic income at the northern frontier to the U.S. and b) those Mexican states surrounding the main producer of tobacco (Nayarit). 쑖 2005 IMSS. Published by Elsevier Inc. Key Words: Mortality, COPD, Mexico, Epidemiology, Trends.
Introduction Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases (1,2). Also, COPD could be associated with symptoms related to breathing (i.e., chronic coughing, exercise dyspnea, sputum
Address reprint requests to: Francisco Javier Lo´pez Antun˜ano, Departamento de Investigacio´n en Tabaco, Centro de Investigacio´n en Salud Poblacional, Instituto Nacional de Salud Pu´blica, Av. Universidad 655, Colonia Santa Marı´a Ahuacatitla´n, CP 62508, Cuernavaca, Morelos, Me´xico. Telephone: 01-777-3112463; Fax: 01-777-3111148; E-mail: [email protected]
0188-4409/05 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 4 .1 1 .0 01
production, and sibilance) (3). COPD could be present with or without important physical worsening of the symptoms (4). COPD is a major public health problem (5) and is projected to rank fifth in 2020 as a worldwide burden of disease according to a study published by the World Bank/World Health Organization. The Global Burden of Disease Study estimated the fraction of mortality and disability attributable to COPD using the disability-adjusted life year (DALY). According to projections, COPD will be the fifth leading cause of DALYs lost worldwide in 2020 (in 1990 it ranked twelfth) (6). Kuller et al. (7) concluded that COPD was the underlying cause for only one third of all death certificates listing COPD as cause of death. The World Health Report (1998) reports that COPD kills 2.9 million adults every year. COPD is the
쑖 2005 IMSS. Published by Elsevier Inc.
Tovar-Guzma´n et al. / Archives of Medical Research 36 (2005) 65–69
For the analyzed period (1980–2002), a total of 230,463 COPD cases from the Republic of Mexico were studied; 134,579 men and 95,884 women (age group 35–94 years) with an age ratio of 1.4:1.0. Change percentage 1980–2002 for males was ⫹228% and ⫹226% for females; for both sexes it was 227%. Crude mortality rate for males due to COPD varied from 37 cases in 1980 to 61 per 100,000 men by year 2002 (increase: 65%). The crude mortality rate for females due to COPD increased from 27 in 1980 to 43 deaths per 100,000 women by the year 2002 (increase: 56%). For comparison, the age-adjusted mortality rate due to COPD increased from 17 cases in 1980 to 29 per 100,000 men by year 2002 (increase: 72%). The age-adjusted mortality rate due to COPD increased from 11 deaths/100,000 women in 1980 to 16/100,000 women by the year 2002 (increase: 50%). The crude and age-adjusted mortality rates due to COPD in both sexes showed a gradual increase up to 1998 to a decrease slowly by 2002 (Figure 1). For the period 1980–2002, the trend of the specific mortality rates due to COPD increases as the age quinquennium group ranges from the lowest rates (group 35–39 years: rate 0.6 cases/100,000 inhabitants by the year 2002) to the highest rate (group 75⫹ years: rate of 609 deaths/100,000 inhabitants also by the year 2002) (Figure 2). The absolute number of deaths is strongly dependent on the total number of people in a specific age group. We assume the absolute number of people born in 1870 and born in 1900 to be the same. Of the birth cohort of 1870, fewer people will reach the age of 75 because life expectancy
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The total number of deaths due to COPD was obtained from the archives edited by the National Institute of Statistics, Geography and Informatics (Mexico), whose database has been produced since 1979 (14). Analyzed variables were age, gender, Mexican state, cause, year of death and birth year of all cases studied. The variable “cause” in this analysis corresponds to that registered in the WHO International Classification of Diseases (15,16). The population denominators were registered in census VIII, IX, and X, whose projections for 1970–2010 were edited by the National Population Council (17). The crude and age-adjusted mortality rates (quinquennium groups) were calculated using the indirect standardization method, and the population published by the World Health Organization (18). For better visualization of the analysis, trends of specific mortality rates were analyzed by quinquennium age groups (1980–2002). We used logarithmic scale for the axis of the “y” values, in contrast with the trends of the crude and adjusted mortality rates in normal scale. Trends of the crude and adjusted rates were estimated by age groups, death quinquennium, and by birth decade, using as a starting point (origin) the year 1870 and the end, the decade of the 1960s. A simple linear regression analysis was done in which the dependent variables were the absolute values of the deaths
Results
Rates per 100,000 inhabitants
Materials and Methods
and the independent variables were each year of the studied period. Furthermore, the residual analysis was done according to Jacknife in order to demonstrate the adequacy of the model.
80
fifth cause of death worldwide (only after ischemic heart disease, vascular brain disease, low acute pulmonary disease, and tuberculosis) and the fifth most prevalent disease in 1997 (8). During the twenty-first century, a strong increment of COPD mortality is being observed in developing countries, particularly in China (9). The mortality for COPD is increasing, especially in countries with an older population (10). Since 1960, mortality associated with COPD has increased, especially in men. COPD is attributed to increase in tobacco smoking, particularly in men and in those persons older than 35 years (11). Recent estimates of the relative risks for COPD mortality among tobacco smokers compared with nonsmokers varied from relative risk (RR) 2.0 to 32.0, depending upon age, gender, and smoking history (12). It has been established that between 80 and 90% of all patients with COPD diagnosis have a history of tobacco smoking (13). The objective of this work is to describe and analyze the magnitude, risk, comparability, and COPD absolute and age-adjusted mortality trends in Mexico for the period between 1980 and 2002. This work will formulate a hypothesis related to better knowledge of the epidemiology and natural history of the disease and will give arguments for decision making in development of public health programs and services for strengthening the integrated management of tobacco consumption in Mexico and in other countries.
19
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Calendar years Crude female
Adjusted fem
Crude male
Adjusted male
Figure 1. Crude and Adjusted Mortality Rates due to COPD, according to sex (Mexico 1980–2002).
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Figure 2. Trends of the specific mortality rates due to COPD (Mexico 1980–2002).
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Figure 4. Standardized mortality ratio due to COPD in Mexico (1980– 2002).
increases. The larger group of people aged 75⫹ born in 1900 will probably have a higher number of COPD deaths, although the mortality rates in both birth cohorts may be the same (Figure 3). The behavior of the mortality due to COPD by country regions was measured by means of the Standardized Mortality Ratio per Mexican states. The Mexican states located in the northern and central areas of the country present a higher risk of dying from COPD than those Mexican states located in central and southern areas (Figure 4). The simple linear regression coefficient, as measured between the dependent variable (absolute values) and the independent variable (year of death), shows an increment coefficient of 93 cases per increment/year in males (age group 35–74), and 61 cases per increment/year in females (age group 35–74). For the age group 35–94 years, the annual increase for males is 288 cases). These results were
statistically significant and the regression model was validated by residual analysis (Table 1).
Discussion Most of the information available on COPD (prevalence, morbidity, and mortality) comes from developed countries. Even in those countries, accurate epidemiologic data on COPD are difficult and expensive to collect. Prevalence and morbidity data greatly underestimate the total burden of COPD because the disease is usually not diagnosed until it
Table 1. Regression coefficient and residual analysis by sex and age between death year and number of deaths due to COPD (Mexico: 1980–2002) Regression Coefficient
100000
Number of Deaths
10000
1000
100
Sex and age
β
p
R2
CI 95%
Male 35/74 Female 35/74 Total 35/74
92.62 61.34 153.97
0.000 0.000 0.000
0.9763 0.9660 0.9752
(86.07, 99.16) (56.12, 66.57) (142.83, 165.10)
Male 35/94 Female 35/94 Total 35/94
288.31 210.88 499.20
0.000 0.000 0.000
0.9852 0.9827 0.9858
(272.27, 304.36) (198.19, 223.58) (472.02, 526.38)
Residual Analysis 10
1 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960
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SD
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Prob ⬎Z*
Prob χ2 **
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0.0141 0.0139 0.0189
1.1321 1.1051 1.1340
1.2815 1.2212 1.2860
0.09158 0.38340 0.02333
0.0582 0.6022 0.1823
Male 35/94 Female 35/94 Total 35/94
0.0119 0.0078 0.0120
1.1045 1.0758 1.1003
1.2200 1.1574 1.2108
0.17456 0.95718 0.16340
0.0893 0.4132 0.1419
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Figure 3. Trends of the absolute values of COPD deaths by birth year and age group (Mexico).
*Shapiro–Wilk. **Cook–Weisberg Test.
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Tovar-Guzma´n et al. / Archives of Medical Research 36 (2005) 65–69
is clinically apparent and moderately or severely advanced. The imprecise and variable definitions of COPD have made it hard to quantify the morbidity and mortality of this disease in developed (19) and developing countries, including our database in Mexico. Mortality data also underestimate COPD as a cause of death because the disease is more likely to be cited as a contributory than as an underlying cause of death or may not be cited at all (20). The results show a constant increment of the COPD crude and adjusted mortality rates trend until 1998, when a gradual decrease began. This fact is probably due to the change in definition made by the World Health Organization (International Classification of Diseases Ed IX to X), an effect of decreased tobacco smoking, and aging of the total population. It is probably not due to differences in clinical diagnosis interpretation. The implications are high cost in terms of retirement, hospital care, medical treatment, and rehabilitation that leads to many millions of dollars. In Mexico we have very few studies to determine the problems involved in COPD distribution. In the Global Burden of Disease Study conducted under the auspices of the WHO and the World Bank (21), the worldwide prevalence of COPD in 1990 was estimated to be 9/1,000 in men and 7/1,000 in women. However, these estimates include all ages and underestimate the true prevalence of COPD in older adults. The limited data that are available indicate that morbidity due to COPD increases with age and is greater in men than in women (22). In 1998, it was estimated that there were over 1.2 billion smokers in the world, approximately one-third of the global population aged 15 or older; 800 million of these smokers are in developing countries. The global burden of COPD baseline scenario for 2020 considers 209 million in Latin America out of 4,726 million for the world (23). The annual mortality rate standardized by age per 100,000 inhabitants (early 1990) in selected countries of the Americas varied as follows: in men from Argentina [17], Canada [45], Chile [41], Mexico [27], and the U.S. [45]. In women, these rates were Argentina [6], Canada [17], Chile [19], Mexico [15], and in the U.S. [24] (24). In Mexico, for the year 2002 the male/female ratio was 1.4:1.0 (R. Vieyra Cerrillo, personal communication, 2004). By the year 2001, the general mortality of COPD (for WHO International Diseases Classification (IX Revision Code 162.0⫺162.9; X Revision Code C33, C34.0–C34.9) (15,16) represents the sixth cause of death, after diabetes mellitus, ischemic heart disease, cirrhosis, stroke and some perinatal diseases. Mortality rate for COPD was 16 deaths per 100,000 inhabitants. It represents the seventh cause of the general mortality rate in men of 18 per 100,000 men and the fifth in women with 15 deaths/100,000 women. It also represents the fourth cause of general mortality in postproductive age (65 years or more) with a rate of 285 cases per 100,000 inhabitants. In productive age it represents the 18th cause of death (3/100,000 inhabitants). It was the 11th cause
of in-hospital mortality 3,137 deaths and a rate of 76 cases per 100,000 releases within the National Health System (25). The highest standardized mortality rate due to COPD was in the state of Aguascalientes (36 cases/100,000 women and 55 cases/100,000 men). The Standard Population was calculated by WHO 2001 (26). COPD death rates are very low among persons ⬍45 years of age but then increase with age, and COPD becomes the fourth or fifth leading cause of death among persons ⬎45 years of age (27). These facts could be related to the average daily consumption of cigarettes that increased from 7.5 to 9.8 between the years 1992 and 1998. It was estimated that 90% of “smoker homes” consumed up to one package per day. The proportion of non-filter cigarettes increased from 0.4 to 4.8% between 1992 and 1998, with a larger increase in 1996 (27). In summary, the oldest cohorts of the studied population showed the highest COPD mortality absolute value. Due to the higher tobacco purchasing availability and proximity to the U.S., the geographic risk of dying from COPD is concentrated in two regions: a) the three Mexican states of higher economic income at the northern frontier to the U.S. and b) those Mexican states surrounding the main tobacco producer.
Acknowledgments We gratefully acknowledge the Grant Administration Division, Resources Branch, International Development Research Centre, Research for International Tobacco Control, for partial financial support (File: 001726-041).
References 1. Pauwels RA, Buist AS, Calverley PM, Jenkins CR, Hurd SS. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. NHLBI/WHO Global Initiative for Chronic Obstructive Lung Disease (GOLD) Workshop summary. Am J Respir Crit Care Med 2001;163:1256–1276. 2. American Thoracic Society. Standards for the diagnosis and care of patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1995;152(5 Pt 2):S77–S121. 3. Rennard SI. COPD: overview of definitions, epidemiology, and factors influencing its development. Chest 1998;113(4 Suppl):235S–241S. 4. National Center for Health Statistics. Deaths: final data for 1999. Hyattsville, MD: US Department of Health and Human Services, CDC, 2001. National Vital Statistics Report; vol 49, no. 8. Available at http// www.cdc.gov/nchs/releases/01facts/99mortality.htm 5. National Heart, Lung, and Blood Institute. Morbidity & Mortality: Chartbook on Cardiovascular, Lung, and Blood Diseases. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1998. Available from: URL: http:// www.nhlbi.nih.gov/nhlbi/seiin/other/cht-book/htm 6. Murray CJL, Lopez AD. The Global Burden of Disease: A Comprehensive Assessment of Mortality and Disability from Diseases, Injuries and Risk Factors in 1990 and Projected to 2020. Cambridge, MA: Harvard University Press; 1996. 7. Kuller LH, Ockene JK, Townsend M, Browner W, Meilahn E, Wentworth DN. The epidemiology of pulmonary function and COPD
COPD Mortality Trends in Mexico
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mortality in the multiple risk factor intervention trial. Am Rev Respir Dis 1989;140(3 Pt 2):S76. World Health Report. Life in the 21st century. A vision for all. Geneva: World Health Organization;1998. Niu SR, Yang GH, Chen ZM, Wang JL, Wang GH, He XZ, Schoepff H, Boreham J, Pan HC, Peto R. Emerging tobacco hazards in China: 2. Early mortality results from a prospective study. Br Med J 1998;317: 1423–1424. Talitha L, Feenstra M, Van Genugten LL, Hoogenveen RT, Wouters EF, Rutten-Van Mo¨lken MPMH. The impact of aging and smoking on the future burden of chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001;164(4):590–596. Speizer FE. The rise in chronic obstructive pulmonary disease. Overview and summary. Am Rev Respir Dis 1989;140:S106–S107. British Thoracic Society. BTS Guidelines for the management of chronic obstructive pulmonary disease. Thorax 1997;52(Suppl 5): S1–S28. Mannino DM, Homa DM, Akinbami L, Ford ES, Redd SC. Chronic obstructive pulmonary disease surveillance—United States, 1971–2000. MMWR CDC Surveill Summ 2002;51(6):1–6. Instituto Nacional de Estadı´stica, Geografı´a e Informa´tica (INEGI) http://www.inegi.gob.mx/est/default.asp?c=2346 WHO International Classification of Diseases IX Ed. Geneva 1980– 1997. WHO International Classification of Diseases X Ed. Geneva 1998– 2002. Consejo Nacional de Poblacio´n, CONAPO. http://www.conapo.gob.mx Proyeccio´n de Poblacio´n 1970–2010.
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18. Santos Silva I. International Agency for Cancer Research, WHO: Cancer Epidemiology: Principles and Methods. Lyon, France;1999. 19. Pride NB, Vermeire P, Allegra L. Diagnostic labels applied to model case histories of chronic airflow obstruction: responses to a questionnaire in 11 North American and western European countries. Eur Respir J 1989;2:702–709. 20. Mannino DM, Brown C, Giovino GA. Obstructive lung disease deaths in the United States from 1979 through 1993: an analysis using multiplecause mortality data. Am J Respir Crit Care Med 1997;156:814–818. 21. Murray CJL, Lopez AD. Evidence-based health policy lessons from the Global Burden of Disease Study. Science 1996;274:740–743. 22. National Heart, Lung, and Blood Institute. Morbidity & Mortality: Chartbook on Cardiovascular, Lung, and Blood Diseases. U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, Bethesda, MD. 1998. Available from: URL: http:// www.nhlbi.nih.gov/nhlbi/seiin/other/cht-book/htm. 23. Demographics and health effects. Office on Smoking and Health. National Center for Chronic Disease Prevention and Health Promotion. Centers for Disease Control and Prevention. Atlanta, GA (http:// www.treatobacco.net) 24. da Costa e Silva VL, Koifman S. Smoking in Latin America: a major public health problem. Cad Saude Publica 1998;14(Suppl 3):99–108. 25. http://www.salud.gob.mx/apps/htdocs/estadı´sticas/sinais.php 26. World Health Report. World Health Organization, Geneva 2000. Available from URL: http://www.who.int/whr/2000/en/statistics.htm 27. Sesma-Vazquez S, Campuzano-Rincon JC, Carreon-Rodriguez VG, Knaul F, Lopez-Antunano FJ, Hernandez-Avila M. Trends of tobacco demand in Mexico: 1992–1998. Salud Publica Mex 2002;44(Suppl 1): S82–S92.
ORIGINAL ARTICLE
Recent Trends in Mortality Due to Chronic Obstructive Pulmonary Disease (COPD) in Mexico, 1980–2002 Victor Jose´ Tovar Guzma´n, Francisco Javier Lo´pez Antun˜ano and Norma Rodrı´guez Salgado Departamento de Investigacio´n en Tabaco, Centro de Investigacio´n en Salud Poblacional, Instituto Nacional de Salud Pu´blica, Cuernavaca, Morelos, Me´xico Received for publication May 31, 2004; accepted October 18, 2004 (04/001).
Background. Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation that is not fully reversible. Changes in classification have a major impact on reported mortality rates. Methods. Between 1980 and 2002, 230,463 COPD cases were studied (age group 35⫺94 years); 134,579 men; 95,884 women. Results. The crude mortality rate varied from 37 (1980) to 61 per 100,000 men (2002), (increase: 65%). The crude mortality rate for females increased from 27 (1980) to 43 deaths per 100,000 women (2002), (increase: 56%). The trends of the absolute values by birth year and age groups are higher as age increases. As age of death comes down and the birth cohort increases, the absolute values decrease. The Mexican states located in the northern and central areas present a higher risk for dying. There is an increment coefficient of 93 cases per increment year in males (age group 35–74), and 61 cases per increment year in females (age group 35–74 years). For the age group 35–94 years, the annual increase for males is 288 cases. These results were statistically significant, and the regression model was validated by residual analysis. Conclusions. The oldest cohorts of the studied population showed the highest COPD mortality absolute values. The geographic risk of dying from COPD is concentrated in two regions: a) the three Mexican states of higher economic income at the northern frontier to the U.S. and b) those Mexican states surrounding the main producer of tobacco (Nayarit). 쑖 2005 IMSS. Published by Elsevier Inc. Key Words: Mortality, COPD, Mexico, Epidemiology, Trends.
Introduction Chronic obstructive pulmonary disease (COPD) is a disease state characterized by airflow limitation that is not fully reversible and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases (1,2). Also, COPD could be associated with symptoms related to breathing (i.e., chronic coughing, exercise dyspnea, sputum
Address reprint requests to: Francisco Javier Lo´pez Antun˜ano, Departamento de Investigacio´n en Tabaco, Centro de Investigacio´n en Salud Poblacional, Instituto Nacional de Salud Pu´blica, Av. Universidad 655, Colonia Santa Marı´a Ahuacatitla´n, CP 62508, Cuernavaca, Morelos, Me´xico. Telephone: 01-777-3112463; Fax: 01-777-3111148; E-mail: [email protected]
0188-4409/05 $–see front matter. Copyright d o i : 1 0 .1 0 16 / j . a rc m e d .2 00 4 .1 1 .0 01
production, and sibilance) (3). COPD could be present with or without important physical worsening of the symptoms (4). COPD is a major public health problem (5) and is projected to rank fifth in 2020 as a worldwide burden of disease according to a study published by the World Bank/World Health Organization. The Global Burden of Disease Study estimated the fraction of mortality and disability attributable to COPD using the disability-adjusted life year (DALY). According to projections, COPD will be the fifth leading cause of DALYs lost worldwide in 2020 (in 1990 it ranked twelfth) (6). Kuller et al. (7) concluded that COPD was the underlying cause for only one third of all death certificates listing COPD as cause of death. The World Health Report (1998) reports that COPD kills 2.9 million adults every year. COPD is the
쑖 2005 IMSS. Published by Elsevier Inc.
Tovar-Guzma´n et al. / Archives of Medical Research 36 (2005) 65–69
For the analyzed period (1980–2002), a total of 230,463 COPD cases from the Republic of Mexico were studied; 134,579 men and 95,884 women (age group 35–94 years) with an age ratio of 1.4:1.0. Change percentage 1980–2002 for males was ⫹228% and ⫹226% for females; for both sexes it was 227%. Crude mortality rate for males due to COPD varied from 37 cases in 1980 to 61 per 100,000 men by year 2002 (increase: 65%). The crude mortality rate for females due to COPD increased from 27 in 1980 to 43 deaths per 100,000 women by the year 2002 (increase: 56%). For comparison, the age-adjusted mortality rate due to COPD increased from 17 cases in 1980 to 29 per 100,000 men by year 2002 (increase: 72%). The age-adjusted mortality rate due to COPD increased from 11 deaths/100,000 women in 1980 to 16/100,000 women by the year 2002 (increase: 50%). The crude and age-adjusted mortality rates due to COPD in both sexes showed a gradual increase up to 1998 to a decrease slowly by 2002 (Figure 1). For the period 1980–2002, the trend of the specific mortality rates due to COPD increases as the age quinquennium group ranges from the lowest rates (group 35–39 years: rate 0.6 cases/100,000 inhabitants by the year 2002) to the highest rate (group 75⫹ years: rate of 609 deaths/100,000 inhabitants also by the year 2002) (Figure 2). The absolute number of deaths is strongly dependent on the total number of people in a specific age group. We assume the absolute number of people born in 1870 and born in 1900 to be the same. Of the birth cohort of 1870, fewer people will reach the age of 75 because life expectancy
70 60 50 40 30 20 10
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The total number of deaths due to COPD was obtained from the archives edited by the National Institute of Statistics, Geography and Informatics (Mexico), whose database has been produced since 1979 (14). Analyzed variables were age, gender, Mexican state, cause, year of death and birth year of all cases studied. The variable “cause” in this analysis corresponds to that registered in the WHO International Classification of Diseases (15,16). The population denominators were registered in census VIII, IX, and X, whose projections for 1970–2010 were edited by the National Population Council (17). The crude and age-adjusted mortality rates (quinquennium groups) were calculated using the indirect standardization method, and the population published by the World Health Organization (18). For better visualization of the analysis, trends of specific mortality rates were analyzed by quinquennium age groups (1980–2002). We used logarithmic scale for the axis of the “y” values, in contrast with the trends of the crude and adjusted mortality rates in normal scale. Trends of the crude and adjusted rates were estimated by age groups, death quinquennium, and by birth decade, using as a starting point (origin) the year 1870 and the end, the decade of the 1960s. A simple linear regression analysis was done in which the dependent variables were the absolute values of the deaths
Results
Rates per 100,000 inhabitants
Materials and Methods
and the independent variables were each year of the studied period. Furthermore, the residual analysis was done according to Jacknife in order to demonstrate the adequacy of the model.
80
fifth cause of death worldwide (only after ischemic heart disease, vascular brain disease, low acute pulmonary disease, and tuberculosis) and the fifth most prevalent disease in 1997 (8). During the twenty-first century, a strong increment of COPD mortality is being observed in developing countries, particularly in China (9). The mortality for COPD is increasing, especially in countries with an older population (10). Since 1960, mortality associated with COPD has increased, especially in men. COPD is attributed to increase in tobacco smoking, particularly in men and in those persons older than 35 years (11). Recent estimates of the relative risks for COPD mortality among tobacco smokers compared with nonsmokers varied from relative risk (RR) 2.0 to 32.0, depending upon age, gender, and smoking history (12). It has been established that between 80 and 90% of all patients with COPD diagnosis have a history of tobacco smoking (13). The objective of this work is to describe and analyze the magnitude, risk, comparability, and COPD absolute and age-adjusted mortality trends in Mexico for the period between 1980 and 2002. This work will formulate a hypothesis related to better knowledge of the epidemiology and natural history of the disease and will give arguments for decision making in development of public health programs and services for strengthening the integrated management of tobacco consumption in Mexico and in other countries.
19
66
Calendar years Crude female
Adjusted fem
Crude male
Adjusted male
Figure 1. Crude and Adjusted Mortality Rates due to COPD, according to sex (Mexico 1980–2002).
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Figure 2. Trends of the specific mortality rates due to COPD (Mexico 1980–2002).
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Figure 4. Standardized mortality ratio due to COPD in Mexico (1980– 2002).
increases. The larger group of people aged 75⫹ born in 1900 will probably have a higher number of COPD deaths, although the mortality rates in both birth cohorts may be the same (Figure 3). The behavior of the mortality due to COPD by country regions was measured by means of the Standardized Mortality Ratio per Mexican states. The Mexican states located in the northern and central areas of the country present a higher risk of dying from COPD than those Mexican states located in central and southern areas (Figure 4). The simple linear regression coefficient, as measured between the dependent variable (absolute values) and the independent variable (year of death), shows an increment coefficient of 93 cases per increment/year in males (age group 35–74), and 61 cases per increment/year in females (age group 35–74). For the age group 35–94 years, the annual increase for males is 288 cases). These results were
statistically significant and the regression model was validated by residual analysis (Table 1).
Discussion Most of the information available on COPD (prevalence, morbidity, and mortality) comes from developed countries. Even in those countries, accurate epidemiologic data on COPD are difficult and expensive to collect. Prevalence and morbidity data greatly underestimate the total burden of COPD because the disease is usually not diagnosed until it
Table 1. Regression coefficient and residual analysis by sex and age between death year and number of deaths due to COPD (Mexico: 1980–2002) Regression Coefficient
100000
Number of Deaths
10000
1000
100
Sex and age
β
p
R2
CI 95%
Male 35/74 Female 35/74 Total 35/74
92.62 61.34 153.97
0.000 0.000 0.000
0.9763 0.9660 0.9752
(86.07, 99.16) (56.12, 66.57) (142.83, 165.10)
Male 35/94 Female 35/94 Total 35/94
288.31 210.88 499.20
0.000 0.000 0.000
0.9852 0.9827 0.9858
(272.27, 304.36) (198.19, 223.58) (472.02, 526.38)
Residual Analysis 10
1 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960
Sex and age
Mean
SD
Variance
Prob ⬎Z*
Prob χ2 **
Male 35/74 Female 35/74 Total 35/74
0.0141 0.0139 0.0189
1.1321 1.1051 1.1340
1.2815 1.2212 1.2860
0.09158 0.38340 0.02333
0.0582 0.6022 0.1823
Male 35/94 Female 35/94 Total 35/94
0.0119 0.0078 0.0120
1.1045 1.0758 1.1003
1.2200 1.1574 1.2108
0.17456 0.95718 0.16340
0.0893 0.4132 0.1419
Year of Birth 35-39
40-44
45-49
50-54
60-64
65-69
70-74
75 +
55-59
Figure 3. Trends of the absolute values of COPD deaths by birth year and age group (Mexico).
*Shapiro–Wilk. **Cook–Weisberg Test.
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Tovar-Guzma´n et al. / Archives of Medical Research 36 (2005) 65–69
is clinically apparent and moderately or severely advanced. The imprecise and variable definitions of COPD have made it hard to quantify the morbidity and mortality of this disease in developed (19) and developing countries, including our database in Mexico. Mortality data also underestimate COPD as a cause of death because the disease is more likely to be cited as a contributory than as an underlying cause of death or may not be cited at all (20). The results show a constant increment of the COPD crude and adjusted mortality rates trend until 1998, when a gradual decrease began. This fact is probably due to the change in definition made by the World Health Organization (International Classification of Diseases Ed IX to X), an effect of decreased tobacco smoking, and aging of the total population. It is probably not due to differences in clinical diagnosis interpretation. The implications are high cost in terms of retirement, hospital care, medical treatment, and rehabilitation that leads to many millions of dollars. In Mexico we have very few studies to determine the problems involved in COPD distribution. In the Global Burden of Disease Study conducted under the auspices of the WHO and the World Bank (21), the worldwide prevalence of COPD in 1990 was estimated to be 9/1,000 in men and 7/1,000 in women. However, these estimates include all ages and underestimate the true prevalence of COPD in older adults. The limited data that are available indicate that morbidity due to COPD increases with age and is greater in men than in women (22). In 1998, it was estimated that there were over 1.2 billion smokers in the world, approximately one-third of the global population aged 15 or older; 800 million of these smokers are in developing countries. The global burden of COPD baseline scenario for 2020 considers 209 million in Latin America out of 4,726 million for the world (23). The annual mortality rate standardized by age per 100,000 inhabitants (early 1990) in selected countries of the Americas varied as follows: in men from Argentina [17], Canada [45], Chile [41], Mexico [27], and the U.S. [45]. In women, these rates were Argentina [6], Canada [17], Chile [19], Mexico [15], and in the U.S. [24] (24). In Mexico, for the year 2002 the male/female ratio was 1.4:1.0 (R. Vieyra Cerrillo, personal communication, 2004). By the year 2001, the general mortality of COPD (for WHO International Diseases Classification (IX Revision Code 162.0⫺162.9; X Revision Code C33, C34.0–C34.9) (15,16) represents the sixth cause of death, after diabetes mellitus, ischemic heart disease, cirrhosis, stroke and some perinatal diseases. Mortality rate for COPD was 16 deaths per 100,000 inhabitants. It represents the seventh cause of the general mortality rate in men of 18 per 100,000 men and the fifth in women with 15 deaths/100,000 women. It also represents the fourth cause of general mortality in postproductive age (65 years or more) with a rate of 285 cases per 100,000 inhabitants. In productive age it represents the 18th cause of death (3/100,000 inhabitants). It was the 11th cause
of in-hospital mortality 3,137 deaths and a rate of 76 cases per 100,000 releases within the National Health System (25). The highest standardized mortality rate due to COPD was in the state of Aguascalientes (36 cases/100,000 women and 55 cases/100,000 men). The Standard Population was calculated by WHO 2001 (26). COPD death rates are very low among persons ⬍45 years of age but then increase with age, and COPD becomes the fourth or fifth leading cause of death among persons ⬎45 years of age (27). These facts could be related to the average daily consumption of cigarettes that increased from 7.5 to 9.8 between the years 1992 and 1998. It was estimated that 90% of “smoker homes” consumed up to one package per day. The proportion of non-filter cigarettes increased from 0.4 to 4.8% between 1992 and 1998, with a larger increase in 1996 (27). In summary, the oldest cohorts of the studied population showed the highest COPD mortality absolute value. Due to the higher tobacco purchasing availability and proximity to the U.S., the geographic risk of dying from COPD is concentrated in two regions: a) the three Mexican states of higher economic income at the northern frontier to the U.S. and b) those Mexican states surrounding the main tobacco producer.
Acknowledgments We gratefully acknowledge the Grant Administration Division, Resources Branch, International Development Research Centre, Research for International Tobacco Control, for partial financial support (File: 001726-041).
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