Lipoprotein status among urban populations in Bangladesh

Atherosclerosis 223 (2012) 454e457

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Lipoprotein status among urban populations in Bangladesh Sumon Kumar Das a, Abu Syed Golam Faruque a, *, Ashish Kumar Chowdhury a, Mohammod Jobayer Chisti a, Mohammad Anowar Hossain a, Mohammed Abdus Salam a, Tahmeed Ahmed a, Abdullah Al Mamun b a b

International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Bangladesh School of Population Health, University of Queensland, Brisbane, Australia

a r t i c l e i n f o

a b s t r a c t

Article history: Received 16 April 2012 Received in revised form 25 April 2012 Accepted 2 May 2012 Available online 20 June 2012

Objective: Serum lipoprotein is the most important predictor for microvascular diseases, and may be influenced by rapid urbanization. Currently available data are limited, particularly regarding age-specific lipoprotein status in urban Bangladeshi populations. Methods: Blood lipoprotein levels of 51,353 male and female individuals primarily residing in urban Bangladesh were analyzed. De-identified data (collected between January 2005 and December 2011) were extracted from the Clinical Biochemistry Laboratory Data Archive of International Centre for Diarrheal Disease Research, Bangladesh (icddr,b). For analyses, six age categories were created: (i) <20 years, n ¼ 481; (ii) 20e29 years, n ¼ 1602; (iii) 30e39 years, n ¼ 7272; (iv) 40e49 years, n ¼ 13,582; (v) 50e59 years, n ¼ 15,890; and (vi) 60 years and more, n ¼ 12,526. Results: Mean serum levels of TC, LDL, TG, LDL:HDL and TC:HDL were significantly higher among adults 30e39 years old compared to other age groups, regardless of sex. The proportion of high TC and LDL from 2005 to 2011 among individuals aged 30e39 years old varied widely (p < 0.01 for trend and all pairwise tests). Conclusion: 30e39 years old individuals had higher concentration of lipoprotein, which increases microvascular disease risk. Further population-based studies are needed to validate our observations in rural areas of Bangladesh. Ó 2012 Elsevier Ireland Ltd. All rights reserved.

Keywords: Elderly Hyperlipidemia Lipoprotein Urban

1. Introduction Globally, growing urbanization has been associated with escalating population density in metropolitan areas, increasing life expectancy, and rising prevalences of chronic diseases [1e3]. Employment opportunities, transportation and technological developments are among the leading factors for rural-urban migration, as commonly observed in under-resourced countries [4,5]. Migration rates are high among young and middle-aged populations due to better economic prospects in urban areas [6].

* Corresponding author. Centre for Nutrition and Food Security (CNFS), International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh. Tel.: þ88 (0)2 9860 704 (work), þ88 (0)2 900 7936 (home), þ88 (0)1 7487 14593 (mobile), þ88 (0)1 7131 41431 (mobile); fax: þ88 (0)2 882 3116. E-mail addresses: [email protected] (S.K. Das), [email protected] (A.S. Golam Faruque), [email protected] (A.K. Chowdhury), [email protected] (M.J. Chisti), [email protected] (M.A. Hossain), [email protected] (M.A. Salam), tahmeed@ icddrb.org (T. Ahmed), [email protected] (A. Al Mamun). 0021-9150/$ e see front matter Ó 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atherosclerosis.2012.05.002

Rapid industrialization has also led to environmental pollution in the large cities [7]. Dhaka, the capital of Bangladesh is ranked the 20th largest city in the world according to population, with over 14 million residents [8]. The population is growing by an estimated 4.2% per year, among one of the highest rates across the Asian continent [9]. Due to sustained increases of both domestic and foreign investments, mass migration from rural Bangladesh to Dhaka has occurred in the past few decades [10]. Projections suggest Dhaka will be home of 25 million people by 2025 [11]. Overcrowding, sedentary life styles, and changing dietary habits are among important contributing factors of chronic diseases, such as cardiovascular and cerebro-vascular diseases, caused by microvascular disorders. Moreover, higher prevalence of hypercholesterolemia has been reported among urban populations living in different socioeconomic contexts [3,12,13]. Despite the potential relevance for health care and policy, agespecific lipoprotein status among urban residents of Dhaka has not been previously characterized. Furthermore, little is known regarding time trends of lipoprotein status changes and associations with aging.

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Table 1 Mean differences in lipoprotein levels among individuals of different age stratum in urban population. Indicators (mmol/l)

19 yrs (n ¼ 481)

Total cholesterol (TC) High density lipoprotein (HDL) Low density lipoprotein (LDL) Triglyceride (TG) Log transform Triglyceride (TG) TC:HDL LDL:HDL

4.29 1.01 2.70 1.35 0.11 4.47 2.82

      

20e29 yrs (n ¼ 1602)

1.19 0.29 0.93 1.03 0.59 1.41 1.06

4.76 0.97 3.03 1.72 0.36 5.11 3.25

      

30e39 yrs (n ¼ 7272)

1.04 0.24 0.88 1.19 0.59 1.47 1.08

4.99 0.93 3.17 2.05 0.54 5.57 3.52

      

40e49 yrs (n ¼ 13,582)

1.09a 0.22a 0.95a 1.39a 0.59a 1.52a 1.13a

4.92 0.94 3.11 1.97 0.52 5.43 3.42

      

60 yrs (n ¼ 12,526)

50e59 yrs (n ¼ 15,890)

1.11 0.22 0.95 1.25 0.55 1.56 1.16

4.77 0.96 2.98 1.88 0.47 5.13 3.19

      

1.18 0.24 1.01 1.18 0.54 1.47 1.14

4.46 0.99 2.74 1.66 0.36 4.72 2.88

      

1.16 0.25 0.98 1.08 0.54 1.53 1.13

Values reported as mean  Sd, unless otherwise specified. a The mean difference was significant at 0.05 level between 30 and 39 years age group with other age groups.

2. Methods

3. Results

2.1. Study site

Individuals aged 30e39 years had significantly higher levels of serum TC, LDL, TC:HDL, and LDL:HDL and lower level of HDL compared to the other age groups (Table 1). Serum lipid profiles among males and females aged 30e39 years were high (Table 2). However, individuals under 20 years and 60 years and older had increased serum HDL levels, relative to other age groups (Table 1; Fig. 1). Proportions of individuals with high TC increased from 2005 to 2011 among 30e39 year olds. Proportions of high LDL increased among individuals younger than 20 years and 30e39 years old; however decreased among people 60 years and older between 2005 and 2011. High LDL proportions remained static among most other age groups (<20, 40e49, 50e59 years) (Table 3). Concomitantly, the proportion of high serum TG was observed to decrease among individuals younger than 20 years, and older than 40 years. However, the proportion of high HDL level increased among individuals under 20 years, and 30 years and older over the same period (Table 3).

Data were extracted from 58,344 individuals in the Clinical Biochemistry Laboratory Data Archive of International Centre for Diarrheal Disease Research, Bangladesh (icddr,b) between January 2005 and December 2011. We considered 51,353 reasonably healthy individuals our study population; de-identified data were collected on age, sex and lipid profile (TC, HDL, LDL, and TG) of these individuals were analyzed. Individuals included patients of the icddr,b Dhaka Hospital, and also other residents (predominantly city; some suburban) who received similar services for payment. Five milliliter blood samples were collected after overnight fasting from individuals, and assayed for serum total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL) and low density lipoprotein (LDL) with the Enzymatic Colour Method. Currently over 30 samples per day are regularly collected from lipoprotein assays (with overnight fasting) from recommendations of family doctors. Blood specimens from hospitalized diarrheal disease patients are rarely examined for their lipoprotein status.

4. Discussion From previous literature, we hypothesized that serum TC, LDL, TG, TC:HDL and LDL:HDL would be higher among middle-aged (40e59 years) individuals, compared to young adults (20e39 years) and the elderly (60 years and more) [14,15]. Young adults (20e39 years) are expected to have better physical and mental health, compared to older individuals aged 40 years and above. Yet we observed higher lipoprotein levels among younger people, relative to other age groups. While there is currently no ready explanation, however rapid urbanization is associated with reduced open spaces for physical activities, such as walking or jogging, that affect body fats. Other possible factors include: environmental pollution [16e18], climate change [19,20], and changes in dietary habits especially of younger

2.2. Data analysis Descriptive statistics were reported as proportions and means with standard deviations. Participants were divided into six age groups: (i) less than 20 years, n ¼ 481; (ii) 20e29 years, n ¼ 1602; (iii) 30e39 years, n ¼ 7272; (iv) 40e49 years, n ¼ 13,582; (v) 50e59 years, n ¼ 15,890; and (vi) 60 years and older, n ¼ 12,526. Log base transformation adjusted for skewed data distribution. Differences between age categories were assessed by analysis of variance (ANOVA) with alpha <0.05 considered statistically significant. Data were analyzed using Statistical Package for Social Sciences (SPSS) for Windows (Version 15.2; Chicago, IL) and Epi Info (Version 6.0, USD, Stone Mountain, GA).

Table 2 Mean differences in lipoprotein levels among individuals of different sex and age categories in urban Bangladesh. Indicators 19 years n ¼ 481)

20e29 years (n ¼ 1602)

(mmol/l)

Male (340)

Male (954)

TC HDL LDL TG Log TG TC:HDL LDL:HDL

4.26 1.00 2.66 1.39 0.13 4.47 2.78

      

Female (141) 1.17 0.28 0.93 1.02 0.60 1.35 1.00

4.37 1.03 2.81 1.25 1.25 4.49 2.90

      

1.24 0.29 0.94 1.05 1.05 1.56 1.19

4.82 0.92 3.08 1.88 0.46 5.43 3.45

      

30e39 years (n ¼ 7272) Female (648)

1.06 0.21 0.89 1.27 0.57 1.42 1.04

4.66 1.06 2.95 1.50 0.22 4.63 2.94

      

0.99 0.26 0.84 1.02 0.60 1.41 1.08

40e49 years (n ¼ 13,582)

Male (4773)

Female (2499)

5.05  1.13a 0.88  0.18a 3.21  0.98a 2.23  1.44a 0.64  0.57a 5.90.1.46a 3.72  1.12a

4.86 1.02 3.08 1.69 0.34 4.96 3.13

      

Male (8554) 1.00a 0.25a 0.88a 1.21a 0.59a 1.45a 1.03a

4.90 0.89 3.10 2.08 0.57 5.68 3.57

      

Female (5028) 1.14 0.19 0.97 1.32 0.56 1.53 1.15

60 years (n ¼ 12,526)

50e59 years (n ¼ 15,890)

4.96 1.03 3.14 1.78 0.42 5.01 3.16

      

TC ¼ total cholesterol; HDL ¼ high density lipoprotein; LDL ¼ low density lipoprotein; TG ¼ triglyceride. a The mean difference was significant at 0.05 level between 30 and 39 years age group with other age groups.

Male (9862) 1.05 0.24 0.91 1.10 0.54 1.53 1.13

4.59 0.90 2.86 1.89 0.48 5.24 3.25

      

Female (6028) 1.16 0.20 0.99 1.23 0.55 1.50 1.16

5.05 1.06 3.17 1.86 0.48 4.94 3.09

      

Male (8247) 1.15 0.26 1.00 1.10 0.52 1.41 1.10

4.28 0.94 2.62 1.62 0.32 4.73 2.89

      

Female (4279) 1.23 0.23 0.94 1.10 0.55 1.46 1.13

4.82 1.08 2.96 1.75 0.42 4.70 2.87

      

1.16 0.27 1.00 1.03 0.52 1.67 1.13

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S.K. Das et al. / Atherosclerosis 223 (2012) 454e457

6.00 4.99

4.76

5.00

4.92

4.77 4.46

4.29

mmol/L

4.00 3.17

3.03

3.11

3.00

2.05

1.97

1.72

2.00

1.00

2.98

2.70

2.74

1.88

1.66

1.35 0.97

0.93

0.94

0.96

0.99

20-29 y

30-39 Y

40-49 y

50 -59 y

≥60 y

1.01

0.00 ≤19 y

Total cholesterol

HDL

LDL

Triglyceride

Fig. 1. Mean distribution of lipoprotein level among individuals of different age stratum in urban population.

adults (20e39 years) who are more inclined to eat not traditional foods higher in fats [21,22] than older people are adherent to traditional diets. Additionally younger people have increasing access to day-to-day modern amenities leading to reduced physical activity and sedentary life styles. Middle-aged and the elderly, on the other hand, tend to have gradually worsening catabolic and overall metabolic activities of the body; and reduced immune function that increases vulnerability to chronic diseases and physiological disorders [23e25]. They are also more prone to have imbalanced body lipoprotein status than young adults. In this analysis, higher serum lipoprotein status was observed among young adults between 30 and 39 years of age, compared to the other age categories. Proportions of higher serum lipoprotein gradually decreased in individuals 60 years and above. This suggests that urban young adults are at increased risk for higher levels of atherogenic lipoprotein. Serum LDL lipoprotein is the key atherosclerotic agent that deposits into both micro and macro vascular lumen, which causes narrowing of the vascular diameter and reduced distal circulation [26]. As a result, there is hypoperfusion of cells causing cardiovascular as well as cerebrovascular diseases. Previous research shows that hypercholesterolemia is one of the major risk factors for cardiovascular diseases with progressive increase of risk [27e29]. Several life style and behavioral factors including dietary habits, sedentary life style, smoking, hypertension and diabetes mellitus are the leading predictors of cerebro-vascular diseases. Due to science and technology advancements, there are increased sedentary life styles, consumption of high fat fast foods; and overall reduction of daily physical exercises, which may relate to increased atherogenic lipoprotein in blood among individuals of this age group.

Additionally, common use and frequent consumption of certain bio-chemical preservatives in food items might affect atherogenic lipoprotein levels. One study limitation was that we extracted data from a database of reasonably healthy individuals who were advised for assessing their blood samples by their family doctors. This study was not able to consider the reasons individuals may have been requested blood samples, or any factors significantly associated with these disorders. Although the majority of individuals were urban residents, some were from peri-urban areas. We did not adjust for socio-demographic (except age and sex) and life style (e.g. smoking, diet, alcohol use, caloric consumption, physical activity at work and for leisure) factors. However, the strengths of this study included use of a large sample size that facilitates the generalizability of results on urban populations, and high quality laboratory analyses. Despite our limitations, our observations were comparable with other similar studies conducted in several other countries. At the same time, the study captured young adult characteristics, which is largely understudied in Bangladesh, in light of other priorities including maternal-child and elderly populations. Globally, research on lipoprotein status among young adults is also limited. In summary, increases in lipoprotein status among young adults as well as middle-aged individuals may have striking consequences on chronic diseases, particularly among urban populations. This observation calls for the attention of policy makers in order to formulate strategies for mitigating the burden and severity of increasing lipoprotein levels. However, further research is needed to better understand associated predictors of changed lipoprotein status among both urban and rural residents.

Table 3 Hyperlipidemia prevalence across age categories from 2005 to 2011 among urban Bangladesh residents. Indicators

High High High High

TC (>4.44 mmol/l) LDL (2.74 mmol/l) TG (>1.56 mmol/l) HDL (>1.11 mmol/l)

19 years (%)

60 years (%)

20e29 years (%)

30e39 years (%)

40e49 years (%)

50e59 years (%)

2005

2011

p*

2005

2011

p*

2005

2011

p*

2005

2011

p*

2005

2011

p*

2005

2011

p*

36 42 33 40

29 37 20 28

0.45 0.43 0.03 <0.01

58 56 41 19

56 60 40 19

0.63 0.05 0.36 0.96

65 64 56 13

66 65 55 13

0.01 <0.01 0.77 <0.01

65 63 57 14

64 64 52 17

0.30 0.14 0.01 <0.01

60 58 54 18

57 57 47 22

0.68 0.15 <0.01 <0.01

48 49 45 22

43 42 40 24

0.07 0.01 <0.01 <0.01

*p value of chi-square for trend. TC ¼ total cholesterol; HDL ¼ high density lipoprotein; LDL ¼ low density lipoprotein; TG ¼ triglyceride.

S.K. Das et al. / Atherosclerosis 223 (2012) 454e457

Ethical considerations Although we used de-identified data, this secondary data analysis was approved by the Research Review Committee (RRC) and Ethical Review Committee (ERC) of icddr,b. Funding This secondary analysis only included existing information from the Data Archive, and was not funded by any external donors. All laboratory analyses of lipoprotein levels were independently paid for by respective individuals. Acknowledgments We sincerely acknowledge the support of our laboratory colleagues for providing data from their archive; and particularly the Data Archive manager. We would like to express gratitude to those individuals of the analyzed blood samples. References [1] Steyn K, Kazenellenbogen JM, Lombard CJ, Bourne LT. Urbanization and the risk for chronic diseases of lifestyle in the black population of the Cape Peninsula, South Africa. J Cardiovasc Risk 1997;4:135e42. [2] Anand K, Shah B, Yadav K, et al. Are the urban poor vulnerable to noncommunicable diseases? A survey of risk factors for non-communicable diseases in urban slums of Faridabad. Natl Med J India 2007;20:115e20. [3] Allender S, Lacey B, Webster P, et al. Level of urbanization and noncommunicable disease risk factors in Tamil Nadu, India. Bull World Health Organ 2010;88:297e304. [4] Todaro MP. Income expectations, rural-urban migration and employment in Africa. Int Labour Rev 1996;135:421e44. [5] Stark O, Levhari D. On migration and risk in LDCs. Econ Dev Cult Change 1982; 31:191e6. [6] Ashton J. Urban lifestyle and public health in the city. J R Stat Soc 1990;39: 147e56. [7] “America’s most polluted cities”. Forbes. http://www.forbes.com/logistics/ 2006/03/21/americas-most-polluted-cities-cx_rm_0321pollute.html. [8] South Asia e World population day e July 11 (South Asia urban growth) web.worldbank.org countries South Asia. http://www.citypopulation.de/ world/Agglomerations.html. [9] http://www.prb.org/Articles/2001/Urbanization Takes on New Dimensionsin Asias Population Giants.aspx.

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