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Revista Brasileira de Hematologia e Hemoterapia

versão impressa ISSN 1516-8484versão On-line ISSN 1806-0870

Rev. Bras. Hematol. Hemoter. vol.38 no.2 São Paulo abr./jun. 2016

http://dx.doi.org/10.1016/j.bjhh.2016.03.005 

ORIGINAL ARTICLES

Descriptive study of the prevalence of anemia, hypertension, diabetes and quality of life in a randomly selected population of elderly subjects from São Paulo

Jacqueline Lacerdaa 

Matheus Rodrigues Lopesb 

Douglas Patriota Ferreiraa 

Fernando Luiz Affonso Fonsecaa 

Patricia Favaroa  * 

aUniversidade Federal de São Paulo (Unifesp), Diadema, SP, Brazil

bUniversidade Estadual de Campinas (Unicamp), Campinas, SP, Brazil

ABSTRACT

BACKGROUND:

The rapid increase in the aged population has resulted in a growing number of cases of chronic diseases. This increase is an important demographic change that low- and middle-income countries have to face and poses a new challenge to health services. One of the first steps to formulate public policies is to understand the reality of each country's aging population. This study describes the prevalence of anemia, hypertension and diabetes and the overall health status in pre-elderly and elderly subjects enrolled in two primary health care clinics, Eldorado and Piraporinha, in the city of Diadema, São Paulo.

METHOD:

A cross-sectional study was conducted with 373 participants. Clinical data were collected from patient charts and the degree of disability and common mental disorders, as well as demographic data were obtained by interviews.

RESULTS:

The prevalence of anemia was approximately 11% and hypertension was 70% and 81% in Eldorado and Piraporinha, respectively. The frequency of diabetes was 52% in Eldorado and 30% in Piraporinha. The subjects of both health care clinics reported having difficulties in some of their daily physical and instrumental activities, with physical symptoms and emotional disorders.

CONCLUSION:

Anemia, hypertension and diabetes are prevalent in the studied population, and patients showed degrees of dependency and impaired health status.

Keywords: Anemia; Elderly; Erythrocyte indices; Personal functional status; Non-psychotic mental disorders

Introduction

Increases in the proportion of older people are a universal phenomenon. The forecast for this older population (>65 year old) for 2100, across the globe, is more than triple the current number.1 This demographic change is a consequence of socioeconomic growth and increasing prosperity, resulting in a higher average life expectancy.2 However, this aging of the population has an impact on health care systems, in part due to the increase in the number of people with chronic diseases.3

Life expectancy is higher in developed countries however the absolute number of older adults is concentrated in developing countries.4 In the past 50 years, Brazil, the fifth largest country in the world, has experienced a demographic revolution. According to the Brazilian census department, the Instituto Brasileira de Geografia e Estatística, the average life expectancy in Brazil had reached 73 years in 2009 (76.5 and 69 years for women and men, respectively).5 Nevertheless, the corresponding rate of socioeconomic growth and improvement in health care has not kept up with this rapid rate of aging of the Brazilian population.6 Thus, understanding the Brazilian reality of this aging population could help implement local health policies and interventions based on diversities.

The aim of this study was to evaluate the prevalence of anemia, hypertension and diabetes and to correlate these issues with the overall health status in pre-elderly (50-59 years) and elderly patients (age ≥60 years) enrolled in two primary care clinics.

Method

Study design

This is a cross-sectional observational study carried out at two primary referral centers for elderly care, Eldorado and Piraporinha. Both clinics are in the city of Diadema, which along with other cities, belongs to the conurbation of São Paulo. The Eldorado clinic is located in the outskirts of the city and the Piraporinha clinic is located in a more privileged area, in the city center, conferring different geographic contexts to the clinics.

Participants

This study included 373 participants with clinical data being collected between November 2012 and April 2013. All pre-elderly and elderly male and female individuals (50 years or older) of the two clinics were invited to participate in the study. Subjects who did not live in Diadema and individuals who refused to participate in the study were excluded from the study, as were those who were unable to answer the questions due to deafness, blindness, or with difficulties to understand. A simple random sampling method was used. In order to calculate the sample size, the elderly population of Diadema was considered to be approximately 4% of the total population,5 thus using a 95% confidence level and 5% sampling error, the minimum sample size required was 280 subjects.7 All the individuals who participated in the study provided informed written consent. The Ethics Committee of the Universidade Federal de São Paulo (Unifesp) approved the study protocol (#142.778).

Diagnosis of anemia, hypertension and diabetes

Diagnoses of anemia, high blood pressure and diabetes mellitus were based on clinical charts, whenever available. The diagnoses for anemia and diabetes were based on the results from automated hematology and biochemistry analyzers, respectively. Anemia was defined according to World Health Organization criteria8 as a hemoglobin level <13 g/dL in men or <12 g/dL in women. The diagnosis of diabetes was defined based on the current American Diabetes Association (ADA) guidelines, which include a fasting plasma glucose level of ≥7.0 mmol/L (126 mg/dL).9 Hypertension was defined as a consistent (three or more readings by the physician during a medical appointment) systolic blood pressure (SBP) ≥140 mmHg or a diastolic blood pressure (DBP) ≥90 mmHg.10

Procedure

One hundred and seven subjects agreed to complete the Brazilian Older Americans Resources And Services Multidimensional Functional Assessment Questionnaire (BOMFAQ)7and8 and the Self-Reporting Questionnaire (SRQ-20)9and10; both interviews were carried out in person by trained students. Demographic data regarding the number of years of schooling and income were also obtained. The BOMFAQ consists of 15 questions about activities of daily living (ADL), divided into two sub-scales; eight physical ADL (PADL), and seven instrumental ADL (IADL). The PADL included getting into and out of bed, eating, combing the hair, walking on flat surfaces, having a bath/shower, getting dressed, getting to the toilet in time and cutting toenails. The IADL included climbing stairs (one flight), taking medicines on time, walking close to home, shopping, preparing meals, getting off buses and cleaning the house.11 The subjects' responses to the BOMFAQ were analyzed according to two criteria: with or without difficulty to complete the task.

Statistical analysis

All statistical data analyses were performed using the Statistical Package for the Social Sciences (SPSS, version 21.0; IBM Corp., 2012). The Student's t -test, the chi-square test, and the Pearson correlation coefficient with a level of significance of 5% and a 95% confidence interval (95% CI) were used for data analysis. A two-tailed p -value <0.05 was considered statistically significant.

Results

Study population

This report is based on 373 participants; 40% were pre-elderly subjects (50-59 years old) and 60% were women. There were no statistically significant differences in the clinical data (including age and gender) between the health care clinics (Table 1).

Table 1  Clinical characteristics of subjects. 

Characteristic Eldorado Piraporinha p-Valuea
Age (years) – mean (range) 61 (50–93) 62 (50–101) 0.377
Pre-elderly – n (%) 40 (41.7) 115 (41.5)
Elderly – n (%) 56 (58.3) 162 (58.5)
Gender – n (%)
Male 36 (37.5) 105 (37.9) 0.943
Female 60 (62.5) 172 (62.1)
Peripheral blood parameters – mean (range)
Erythrocytes (× 1012 L) 4.63 (2.41–5.8) 4.63 (3.00–6.79 0.401
Hematocrit (%) 41.3 (27.2–51.1) 41.1 (25.1–60.9) 0.504
Hemoglobin (g/dL) 13.9 (9.2–17.8) 13.7 (8.2–20.8) 0.559
Total leukocytes (× 109/L) 6.85 (2.6–11.9) 6.1 (0.8–16.2) 0.460
Mean corpuscular volume 89.4 (65.6–112.9) 89.4 (59.6–101.4) 0.702
MCH (pg/cell) 30.1 (20.3–38.2) 30.3 (18.5–36.8) 0.249
MCHC (g/dL) 33.6 (30.9–36.6) 33.8 (13.0–39.5) 0.461
RDW (%) 13.1 (10.7–27.0) 12.8 (10.1–17.9) 0.151
Platelets (× 109/L) 228 (130–654) 234 (81–454) 0.316
Fasting plasma glucose 117.8 (67–376) 106.14 (43–432) 0.06

MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; RDW: red cell distribution width

aStudent's t -test was used for quantitative variables and the Chi-square test for categorical variables

Prevalence of anemia, diabetes and hypertension

The prevalence of anemia in the studied population was approximately 11% for men and women in both health care clinics with hemoglobin <10 g/dL being found in approximately 2% of the subjects (Table 2).

Table 2  Prevalence of anemia, diabetes and hypertension. 

Eldorado Piraporinha p-Valuea
Anemia – n (%) 11 (11.5) 32 (11.6) 0.9802
Male:female ratio 4:1 11:21 0.9050
Hemoglobin – n (%)
≥10 g/dL 94 (97.9) 270 (97.5) 0.8071
<10 g/dL 2 (2.1) 7 (2.5)
Diabetes – n (%) 25 (52.1) 25 (30.5) 0.0241
Male:female ratio 10:15 11:14 0.7
Hypertension – n (%) 45 (81.8) 55 (69.6) 0.16
Male:female ratio 14:31 23:32 0.37

aChi-square test. Value in bold-face indicate statistically significant differences.

Approximately 52% of the subjects had diabetes in the Eldorado health care clinic which was a significantly higher frequency when compared to Piraporinha, where nearly 30% of the subjects were diabetic (p -value = 0.0241; Table 2).

The frequencies of hypertension were similar in both clinics (70% in Eldorado and 81% in Piraporinha) with no statistically significant difference between genders (Table 2).

Hemoglobin values and age

The Pearson correlation coefficient demonstrated that hemoglobin levels were inversely associated with age (Figure 1). In addition, hemoglobin values were significantly lower in the elderly when compared with the pre-elderly group (Figure 2).

Figure 1 Correlation of hemoglobin values (g/dL) with age (years). 

Figure 2  Distribution of hemoglobin values (g/dL) in pre-elderly and elderly groups (horizontal lines indicate medians). 

Assessment of the degree of dependency and common mental disorders

One hundred and seven subjects were assessed using both the BOMFAQ and the SRQ-20 instruments to evaluate the degree of disability and common mental disorders, respectively. Table 3 shows the sociodemographic data of the sample.

Table 3  Sociodemographic characteristics. 

Eldorado n (%) Piraporinha n (%) p-Valuea
Gender
Male 5 (14.3) 23 (31.9)
Female 30 (85.7) 49 (68.1) 0.05
Education (years)
None 4 (11.4) 8 (11.1) 0.3
1–3 25 (71.4) 38 (52.8)
4–7 2 (5.7) 10 (13.9)
8+ 4 (11.5) 16 (22.2)
Monthly income (R$)b
0–723 15 (44.1) 21 (30) 0.15
724–2172 19 (55.9) 44 (62.9)
2173+ 0 5 (7.1)

aChi-square test

bDuring the period of data collection the minimum Brazilian wage was approximately R$ 724.00, and US$ 1.00 was approximately equal to R$ 2.50

When the subjects were evaluated according to their level of independence, the subjects from the Eldorado health care clinic generally reported having more difficulties in two PADL and two IADL; walking on flat surfaces (44.1%), getting dressed (14.2%), getting off buses (40%) and cleaning the house (50%) (Table 4). Subjects from Eldorado also presented with more physical symptoms and emotional disorders when compared with Piraporinha subjects (Table 5).

Table 4  Difficulty for perform 15 activities of daily life by group. 

Activities Without difficult With difficult p-Valuea
Eldorado n (%) Piraporinha n (%) Eldorado n (%) Piraporinha n (%)
Getting into and out of bed 18 (51.4) 48 (66.8) 17 (48.6) 24 (33.3) 0.1282
Eating 32 (91.4) 70 (97.2) 3 (8.6) 2 (2.8) 0.3275
Combing hair 26 (74.3) 63 (88.7) 9 (25.7) 8 (11.3) 0.0566
Walking on flat surfaces 19 (55.9) 6 (88.9) 15 (44.1) 8 (11.1) 0.0001
Having a bath/shower 30 (85.7) 69 (95.8) 5 (14.3) 3 (4.2) 0.1104
Getting dressed 30 (85.7) 70 (97.2) 5 (14.3) 2 (2.8) 0.0366
Getting to the toilet in time 30 (85.7) 64 (88.9) 5 (14.3) 8 (11.1) 0.754
Cutting toenails 18 (51.4) 37 (51.4) 17 (48.6) 35 (48.6) 0.9969
Climbing stairs (one flight) 17 (48.6) 44 (61.1) 18 (51.4) 28 (38.9) 0.219
Taking medicines on time 28 (80.0) 57 (85.1) 7 (20.0) 10 (14.9) 0.5138
Walking close to home 30 (85.7) 61 (84.7) 5 (14.3) 11 (15.3) 0.8926
Shopping 26 (76.5) 51 (89.5) 8 (23.5) 6 (10.5) 0.0963
Preparing meals 32 (94.1) 48 (96.0) 2 (5.9) 2 (4.0) 1.0
Getting off buses 21 (60.0) 62 (87.3) 14 (40.0) 9 (12.7) 0.0013
Cleaning the house 17 (50.0) 39 (81.3) 17 (50.0) 9 (18.8) 0.0027

aChi-square test. Statistically significance was defined as p -values < 0.05.

Table 5  Results of the SRQ-20 questionnaire by group. 

Yes No p-Valuea
Eldorado n (%) Piraporinha n (%) Eldorado n (%) Piraporinha n (%)
1. Headaches 12 (34.3) 9 (12.5) 23 (65.7) 63 (87.5) 0.0078
2. Poor appetite 14 (40.0) 13 (18.1) 21 (60.0) 59 (81.9) 0.0142
3. Sleeping badly 15 (42.9) 29 (40.3) 20 (57.1) 43 (59.7) 0.7992
4. Easily frightened 17 (48.6) 18 (25.0) 18 (51.4) 54 (75.0) 0.0148
5. Hands shake 9 (25.7) 9 (12.5) 26 (74.3) 63 (87.5) 0.0865
6. Feeling nervous, tense or worried 26 (74.3) 41 (56.9) 9 (25.7) 31 (43.1) 0.082
7. Poor digestion 12 (34.3) 17 (23.6) 23 (65.1) 55 (76.4) 0.2438
8. Trouble thinking clearly 15 (42.9) 8 (11.1) 23 (57.14) 64 (88.9) 0.0002
9. Feeling unhappy 24 (68.6) 32 (44.4) 11 (31.4) 40 (55.6) 0.0191
10. Crying more than usual 12 (32.3) 19 (26.4) 23 (65.7) 53 (73.6) 0.3982
11. Difficulty in enjoying daily activities 14 (40.0) 21 (29.17) 21 (60.0) 51 (70.8) 0.2625
12. Difficulty in making decisions 14 (40.0) 21 (38.9) 21 (60.0) 51 (70.8) 0.9121
13. Daily suffering at work 11 (31.4) 15 (20.8) 24 (68.6) 57 (79.2) 0.2306
14. Unable to play a useful role in life 14 (40.0) 14 (19.4) 21 (60.0) 58 (80.6) 0.0232
15. Lost interest in things 20 (57.1) 26 (36.1) 15 (42.9) 46 (63.9) 0.0392
16. Feeling that you are a worthless person 8 (22.9) 6 (8.3) 27 (77.1) 66 (91.7) 0.063
17. Thoughts of ending your life have been on your mind 6 (17.1) 6 (8.3) 27 (77.1) 66 (91.7) 0.2008
18. Feeling tired all the time 14 (41.2) 16 (22.2) 20 (58.8) 56 (77.8) 0.0432
19. Uncomfortable feelings in your stomach 15 (42.9) 23 (30.6) 20 (57.1) 50 (69.4) 0.2094
20. Easily tired 17 (48.6) 23 (31.9) 18 (51.4) 49 (68.1) 0.0954

aChi-square test. Statistically significance was defined as p -values < 0.05.

Discussion

This study revealed that approximately 11% of the subjects of 50 years of age and older presented anemia according to WHO criteria in both health care clinics. The low prevalence of anemia in our cohort corroborates other studies that also assessed the prevalence of anemia among free-living elderly people; Guralnik et al. presented data regarding a North American population,12 Salive et al. reported on the Epidemiologic Study of the Elderly (EPESE)13 and Inelmen et al. described data in a representative Italian population.14 In the current study, the anemia was mild in the majority of the anemic subjects. In this cohort, normocytic anemia was the most common type of anemia (between 54.5% and 70%), which is consistent with a Brazilian study that studied free-living elderly individuals in southern Brazil.15 Anemia of inflammatory response is most often described as a normocytic normochromic anemia and is usually mild.16 The risk factors linked to the majority of chronic diseases, such as diabetes, have been shown to increase inflammation,17 and in this study, there were high frequencies of both diabetes and hypertension. Despite having observed a negative correlation between hemoglobin levels and age, with lower hemoglobin values in the elderly when compared to the pre-elderly group, it is not believed that these values are due to age. There is a body of evidence that suggests that most cases of anemia in older people are due to poor health and should prompt further investigations in the clinical practice, even when the person has no apparent clinical disease.12and18

With regard to the high prevalence of hypertension in the current cohort, the literature shows that the prevalence of hypertension increases with age in adults19 and can reach a prevalence as high as 80%.20,21,22and23 It is important to point out that hypertension is independently associated with cardiovascular diseases in the elderly.

This study focused on a description of the prevalence of diseases related to elderly individuals and their quality of life. Although there were no social and demographic differences, the study was performed in two contrasting areas of Diadema. While the Piraporinha clinic is located in a more privileged area, in the city center, the Eldorado clinic is located in the poorer outskirts. The subjects that live in the outskirts had significantly lower scores for two PADL and two IADL than the subjects who lived in the city center. Subjects from Eldorado also presented a significantly higher prevalence of minor psychiatric disorders, when compared to the subjects from Piraporinha. Moreover, the prevalence of diabetes was much higher in the Eldorado health care clinic. The literature shows that the incidence of depression and impaired cognitive function increases in elderly individuals with diabetes.24 Moreover, depression in elderly patients with diabetes is a strong predictor of hospitalization and death25; anxiety and stress in the elderly are important health issues frequently associated with poorer physical and emotional well-being.26

Conclusion

Regardless of the location of the health care clinic, there are prevalences of anemia, hypertension and diabetes in the populations of pre-elderly and elderly individuals. Both these groups showed degrees of dependency and impairment of health status. Our findings might aid public health care managers in the targeting of strategies to promote better health in the aging population.

Acknowledgements

Funding for this work was provided by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). The authors would like to thank Raquel Susana Foglio for the English review.

References

1. World Population Prospects [WPP]. The 2010 revision, highlights and advance tables. New York: Department of Economic and Social Affairs PD; 2011. [ Links ]

2. Tonelli M, Riella MC. World Kidney Day 2014: CKD and the aging population. Am J Kidney Dis. 2014;63(3):349-53. [ Links ]

3. Mathers C, Loncar D. Updated projections of global mortality and burden of disease, 2002-2030: data sources, methods and results. Organization WH; 2006. [ Links ]

4. Holtz C. Global health care: issues and policies. Sudbury, MA: Jones & Bartlett; 2008. [ Links ]

5. Search national household sample; 2010. Available from: Available from: http://www.ibge.gov.br/censo2010/primeiros_dados_divulgados/index.php [cited 2014]. [ Links ]

6. Palloni A, Peláez M. History and nature of the study. In: Lebrão ML, Duarte YA, editors. KNOW - health wellness and aging: the SABE project in the municipality of São Paulo - an initial approach. Brasília: Pan American Health; 2003. p. 15-32. [ Links ]

7. Laboratório de Epidemiologia e Estatística - LEE. Available from: Available from: http://www.lee.dante.br/pesquisa.html ; 2000 [cited 17.02.16]. [ Links ]

8. Nutritional anaemias. Report of a WHO scientific group. World Health Organ Tech Rep Ser. 1968;405:5-37. [ Links ]

9. American Diabetes Association. Standards of medical care in diabetes - 2010. Diabetes Care. 2010;33 Suppl. 1:S11-61. [ Links ]

10. Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: the JNC 7 report. JAMA. 2003;289(19):2560-72. [ Links ]

11. Fried LP, Ferrucci L, Darer J, Williamson JD, Anderson G. Untangling the concepts of disability, frailty, and comorbidity: implications for improved targeting and care. J Gerontol A: Biol Sci Med Sci. 2004;59(3):255-63. [ Links ]

12. Guralnik JM, Eisenstaedt RS, Ferrucci L, Klein HG, Woodman RC. Prevalence of anemia in persons 65 years and older in the United States: evidence for a high rate of unexplained anemia. Blood. 2004;104(8):2263-8. [ Links ]

13. Salive ME, Cornoni- Huntley J, Guralnik JM, Phillips CL, Wallace RB, Ostfeld AM, et al. Anemia and hemoglobin levels in older persons: relationship with age, gender, and health status. J Am Geriatr Soc. 1992;40(5):489-96. [ Links ]

14. Inelmen EM, D'Alessio M, Gatto MR, Baggio MB, Jimenez G, Bizzotto MG, et al. Descriptive analysis of the prevalence of anemia in a randomly selected sample of elderly people living at home: some results of an Italian multicentric study. Aging (Milano). 1994;6(2):81-9. [ Links ]

15. Sgnaolin V, Engroff P, Ely LS, Schneider RH, Schwanke CH, Gomes I, et al. Hematological parameters and prevalence of anemia among free- living elderly in south Brazil. Rev Bras Hematol Hemoter. 2013;35(2):115-8. [ Links ]

16. Roy CN. Anemia of inflammation. Hematol Am Soc Hematol Educ Program. 2010;2010:276-80. [ Links ]

17. Prasad S, Sung B, Aggarwal BB. Age-associated chronic diseases require age-old medicine: role of chronic inflammation. Prev Med. 2012;54 Suppl.:S29-37. [ Links ]

18. Izaks GJ, Westendorp RG, Knook DL. The definition of anemia in older persons. JAMA . 1999;281(18):1714-7. [ Links ]

19. Rodriguez BL, Labarthe DR, Huang B, Lopez -Gomez J. Rise of blood pressure with age. New evidence of population differences. Hypertension. 1994;24(6):779-85. [ Links ]

20. Aronow WS, Fleg JL, Pepine CJ, Artinian NT, Bakris G, Brown AS, et al. ACCF/AHA 2011 expert consensus document on hypertension in the elderly: a report of the American College of Cardiology Foundation Task Force on Clinical Expert Consensus Documents. Circulation. 2011;123(21):2434-506. [ Links ]

21. Burt VL, Whelton P, Roccella EJ, Brown C, Cutler JA, Higgins M, et al. Prevalence of hypertension in the US adult population. Results from the Third National Health and Nutrition Examination Survey, 1988-1991. Hypertension . 1995;25(3):305-13. [ Links ]

22. Ostchega Y, Dillon CF, Hughes JP, Carroll M, Yoon S. Trends in hypertension prevalence, awareness, treatment, and control in older U.S. adults: data from the National Health and Nutrition Examination Survey 1988 to 2004. J Am Geriatr Soc . 2007;55(7):1056-65. [ Links ]

23. Egan BM, Zhao Y, Axon RN. US trends in prevalence, awareness, treatment, and control of hypertension, 1988-2008. JAMA . 2010;303(20):2043-50. [ Links ]

24. Meneilly GS, Tessier D. Diabetes in elderly adults. J Gerontol A: Biol Sci Med Sci . 2001;56(1):M5-13. [ Links ]

25. Rosenthal MJ, Fajardo M, Gilmore S, Morley JE, Naliboff BD. Hospitalization and mortality of diabetes in older adults. A 3 -year prospective study. Diabetes Care . 1998;21(2):231-5. [ Links ]

26. Blazer DG. Depression in late life: review and commentary. J Gerontol A: Biol Sci Med Sci . 2003;58(3):249-65. [ Links ]

Received: February 12, 2016; Accepted: March 19, 2016

* Corresponding author . E-mails: patricia.favaro@unifesp.br, favaropb@gmail.com (P. Favaro)

Conflicts of interest The authors declare no conflicts of interest.

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