Abstract
Cardiovascular diseases (CVD) are recognized as major mortality causes and imposes tremendously heavy socio-economic burden worldwide. A vast variety of risk factors have been introduced in the literature known to enhance the incidence of CVD, such as hyperlipidemia. Therefore in order to make an accurate clinical decision it is essential to have appropriate reference ranges for lipids and lipoprotein particles in a particular population. Healthy female (n = 601) and male (n = 617) cases were randomly selected according to certain exclusion criteria from individuals visiting the major University hospital clinics situated in different part of Ahvaz city, Iran, from June 2010 to December 2010. Fasting blood samples (10 ml) were collected and analyzed for total cholesterol, total triglyceride and HDL-C employing enzymatic assays of CHOD-PAP, GPO-PAP and homogenous methods respectively. The samples were obtained such to include the ethnic populations of Persian, Arab. Lore leaving in this city. The data were analyzed statistically by SPSS-18 software. The obtained results were analyzed then age ethnic-wise and reference ranges (mean ± 1SD) were calculated. Remarkable differences between the obtained results for our population with other nations were seen. Also ethnic difference for HDL-C among our cases was noted. The observed significant differences among different nations and ethnicities emphasizes the need for nation-specific, local reference ranges for lipids and lipoproteins particles, to be established.
Keywords: Atherosclerosis, Ethnicity, Gender, Reference range
Introduction
Atherosclerotic coronary artery diseases affect both men and women and account for >4.5 million deaths annually in developing countries [1]. The incidence of such diseases is reported to increases with advancing age over 40 years in male but lower age implicated in this respect as well [2–5].
There are reports contributing the different global burden of vascular diseases in different population to the ethnic and regional variations in cardiovascular risk factors [6–9]. The above-mentioned facts prompted several investigators to conduct studies on types and distribution modes of traditional and newly recognized risk factors in different populations [10, 11] including lipid and lipoproteins indices [12]. These information provided us with a logically acceptable background to embark on a project to clarifying the distribution pattern of lipids and lipoproteins serum concentrations in male and female groups with different age intervals among the three main ethnic populations living in Ahvaz city situated in southern part of Iran.
Materials and Methods
Asymptomatic healthy subjects women (n = 601) and male (n = 617) from different ethnicities Lore, Arab and Persian within three age categories 1–15, 16–55 and >55 years were selected randomly from individuals visiting the major university hospital clinics in different part of the city according to exclusion criteria presented in Table 1 from June 2010 to December 2010. Fasting blood samples of 10 ml were drawn, serum was separated and analyzed for total cholesterol, total triglyceride and HDL-C employing enzymatic CHDD-PAP, GPD-PAP assays and homogenous method respectively. Alcyon auto analyzer, Abbott, USA was employed. Employing Friedwald et al. equation, serum concentrations for LDL-C and VLDL-C were calculated. Reference intervals (Mean ± 1SD) and mean comparison were determined (Table 2, 3, 4, 5 and 6).
Table 1.
Exclusion Criteria
| Remarkable changes in dietary habitués |
| Non-Fasting state |
| History indicative of thyroid dysfunction. |
| History of renal, cardiovascular and liver disease, diabetes mellitus, hypo-hyperthyroidism and any chronic disease. |
| Smoking, alcohol, drugs affecting lipid concentration, hormone therapy and oral contraceptives. |
| History of recent myocardial infarction or major surgery. |
Table 2.
Distribution characteristics for the studied population
| Sex | Male (years) | Female (years) | ||||||
|---|---|---|---|---|---|---|---|---|
| Age interval | 1–15 | 16–55 | >55 | 1–15 | 16–55 | >55 | ||
| Sample size | 617 | 179 | 366 | 72 | 601 | 79 | 460 | 62 |
| Average | 38.311 | 38.502 | 38.407 | 37.347 | 46.376 | 40.730 | 47.622 | 44.209 |
| Standard deviation | 9.575 | 10.182 | 9.294 | 9.507 | 12.171 | 12.531 | 11.790 | 12.384 |
| Standard error | 0.385 | 0.761 | 0.485 | 1.112 | 0.496 | 1.403 | 0.549 | 1.572 |
| Minimum | 16 | 21 | 20 | 16 | 15 | 16 | 15 | 24 |
| Maximum | 64 | 60 | 64 | 60 | 92 | 85 | 92 | 79 |
| Range | 48 | 39 | 44 | 44 | 77 | 69 | 77 | 55 |
| Median | 38 | 38 | 38 | 35 | – | – | – | – |
| Mode | 38 | 42 | 38 | 35 | – | – | – | – |
| Distribution fitting | (N) | (N) | (N) | (N) | (N) | (N) | (N) | (N) |
N Normal
Table 3.
Over-all lipids and lipoproteins serum concentration ranges (mean ± 1SD) for the studied healthy Iranian population
| Analyte | Female (mg/dl) (n = 601) | Male (mg/dl) (n = 617) | p Value |
|---|---|---|---|
| T. Cholesterol | 175.3 ± 37.07 | 177.07 ± 42.48 | 0.43 |
| LDL-C | 107.11 ± 33.52 | 111.48 ± 32.8 | 0.022 |
| VLDL-C | 21.82 ± 10.29 | 25.24 ± 8.72 | 0.0001 |
| HDL-C | 46.37 ± 11.91 | 38.13 ± 9.45 | 0.0001 |
| Triglyceride | 108.95 ± 51.81 | 127.58 ± 54.97 | 0.0001 |
Table 4.
Age and sex-wise lipid and lipoproteins serum concentration (mg/dl) in the studied healthy groups (χ ± 1SD)
| Analyte (mg/dl) | 1–15 years (n = 179) Female 15–55 years (n = 336) >55 years (n = 72) |
1–15 years (n = 79) male 15–55 years (n = 460) >55 years (n = 62) |
p Value |
|---|---|---|---|
| Total cholesterol | 153.3 ± 31.15 | 165.22 ± 35.3 | 0.01 |
| 175.8 ± 22.45 | 178.76 ± 27.3 | 0.09 | |
| 199.5 ± 21.5 | 185.55 ± 34.8 | 0.007 | |
| LDL-C | 93.6 ± 26.75 | 104.87 ± 33.25 | 0.008 |
| 107.0 ± 33.0 | 112.53 ± 31.6 | 0.017 | |
| 125.5 ± 44.15 | 122.81 ± 35.7 | 0.69 | |
| VLDL-C | 18.9 ± 8.1 | 22.43 ± 4.65 | 0.003 |
| 21.3 ± 9.8 | 25.92 ± 8.75 | 0.000001 | |
| 29.4 ± 13.1 | 28.8 ± 10 | 0.52 | |
| HDL-C | 40.65 ± 12.5 | 38.62 ± 10.25 | 0.00001 |
| 47.65 ± 11.8 | 38.34 ± 9.25 | 0.000001 | |
| 44.21 ± 12.35 | 37.34 ± 9.5 | 0.76 | |
| Total triglyceride | 94.94 ± 41.3 | 111.68 ± 42.50 | 0.17 |
| 106 ± 48.75 | 132.6 ± 63 | 0.000001 | |
| 148.32 ± 65.15 | 142 ± 48 | 0.0003 | |
| Total cholesterol/HDL-C ratio | 4.04 ± 1.35 | 4.77 ± 1.3 | 0.00005 |
| 3.91 ± 1.35 | 4.74 ± 1.3 | 0.000001 | |
| 4.99 ± 1.55 | 5.04 ± 1.64 | 0.85 | |
| LDL-C/HDL-C ratio | 2.54 ± 1.22 | 3.06 ± 1.23 | 0.001 |
| 2.43 ± 1.13 | 3.3 ± 1.25 | 0.000001 | |
| 3.05 ± 1.35 | 3.67 ± 1.5 | 0.013 |
LDL-C Low density lipoprotein; VLDL-C Very low density lipoprotein; HDL-C High density lipoprotein
Table 5.
Ethnic-wise lipids and lipoproteins serum concentration (mg/dl) in the studied healthy groups (Mean ± 1SD)
| Analyte | L (128) Female A (231) P (242) |
L (80) Male A (227) P (310) |
p Value | ||
|---|---|---|---|---|---|
| Total cholesterol | p > 0.24 | 178.94 ± 34.5 | p > 0.61 | 178.44 ± 34 | 0.91 |
| 174.15 ± 38.5 | 178.17 ± 55 | 0.36 | |||
| 174.49 ± 37 | 175.93 ± 33.5 | 0.63 | |||
| LDL-C | p > 0.244 | 109.95 ± 31.5 | p > 0.21 | 114.26 ± 30 | 0.32 |
| 105.6 ± 35.05 | 108.87 ± 34 | 0.31 | |||
| 107.05 ± 33 | 112.69 ± 33 | 0.046 | |||
| VLDL-C | p > 0.18 | 22.46 ± 10.25 | p > 0.59 | 23.7 ± 5.8 | 0.81 |
| 22.39 ± 10.1 | 25.42 ± 9.5 | 0.001 | |||
| 20.96 ± 10.5 | 25.52 ± 8.75 | 0.00001 | |||
| Hdl-C | p > 0.53 | 46.65 ± 11.5 | p > 0.01 | 40.76 ± 9 | 0.00001 |
| 45.89 ± 12.5 | 37.48 ± 9.4 | 0.00001 | |||
| 38.29 ± 9.60 | |||||
| 46.69 ± 12 | 0.00001 | ||||
| Total triglyceride | p > 0.23 | 111.77 ± 51 | p > 0.51 | 130.64 ± 100 | 0.07 |
| 111.71 ± 51.25 | 127.34 ± 48 | 0.0008 | |||
| 105.27 ± 52.5 | 126.97 ± 42 | 0.00001 | |||
| Total cholesterol/HDL-C ratio | p > 0.5 | 4.08 ± 1.38 | p > 0.01 | 4.49 ± 1.15 | 0.027 |
| 4.03 ± 1.39 | 4.92 ± 1.5 | 0.00001 | |||
| 3.98 ± 1.34 | 4.77 ± 1.4 | 0.00001 | |||
| LDL-C/HDL-C ratio | p = 0.001 | 2.56 ± 1.15 | p > 0.23 | 3.11 ± 1.9 | 0.009 |
| 3.5 ± 1.25 | 3.27 ± 1.25 | 0.049 | |||
| 2.49 ± 1.14 | 3.33 ± 1.35 | 0.00001 | |||
L Lore ethnicity; A Arab ethnicity; P Persian ethnicity
Table 6.
Mean lipids and lipoproteins concentrations in different populations compared with the studied Iranian population (mg/dl)
| Compared populations | n | Total cholesterol | p Value | HDL-C | p Value | Triglyceride | p Value | |
|---|---|---|---|---|---|---|---|---|
| Men | ||||||||
| All races (20–74 years) Fulwood et.al [14] | USA | 5604 | 221 ± 1.2 | 0.00001 | 45.2 ± 0.4 (n = 4562) | 0.00001 | 145 ± 2.9 (n = 1269) | 0.00001 |
| Noma et.al [15] | Japan | 677 | 184 ± 24 | 0.0002 | 52.6 ± 12.6 | 0.00001 | 95 ± 27 | 0.00001 |
| Malati and Mahesh [13] | India | 1161 | 175.1 ± 34.8 | 0.29 | 41.9 ± 9.8 | 0.00001 | 139.9 ± 63.5 | 0.00004 |
| Li et.al [16] | China | 8572 | 180.1 | 0.07 | 49.03 | 0.00001 | 148.2 | 0.00001 |
| Present study | Iran | 617 | 177.07 ± 42.42 | – | 38.13 ± 9.45 | – | 127.58 ± 54.97 | – |
| Women | ||||||||
| All races (20–74 years) Fulwood et al. [14] | USA | 6260 | 215 ± 1.2 | 0.00001 | 53.7 ± 6.4 (n = 5235) | 0.00001 | 124 ± 2.3 (n = 1111) | 0.00001 |
| Noma et.al [15] | Japan | 467 | 183 ± 24 | 0.00001 | 59 ± 11.5 | 0.00001 | 83 ± 26 | 0.00001 |
| Malati and Mahesh [13] | India | 762 | 175.4 ± 34.3 | 0.95 | 47.2 ± 10.4 | 0.17 | 120 ± 54.8 | 0.00016 |
| Li et.al [16] | China | 6391 | 183.25 | 0.00001 | 57.99 | 0.00001 | 118.125 | 0.00027 |
| Present study | Iran | 601 | 175.3 ± 37.07 | – | 46.37 ± 11.9 | – | 108.95 ± 51.8 | – |
Statistical analyses were done using SPSS-18 software. Independent-sample t test and one-way ANOVA used for comparative study. Significant difference estimated at p value < 0.05.
Results and Discussion
The distribution characteristics for the studied populations are summarized in Table 2. The over-all mean cholesterol for all ages was 175.3 mg/dl for female and 177.07 mg/dl for male groups respectively the confidence limits (Mean ± 1SD) were also presented in Table 3. Although decade-wise analysis of serum cholesterol showed an upward trend in both male and female populations (Fig 1) (Table 4) which seems to be more prominent in female in the third age intervals (>55 years) than in male group although it was not significant (Table 4). Ethnic-based studies showed that Lore ethnic group has the highest serum cholesterol level than other groups with no significant difference between male and females in this respect. In both Arab and Persian groups higher cholesterol serum concentrations were detected in male than in female gender (Table 5). More or less the same trend of changes was observed for LDL-C serum concentration as was seen for total cholesterol.
Fig. 1.
Ethnic-wise (a) and age-wise (b) differences for lipids serum concentrations in the studied populations
The estimated values for HDL-C are shown in Table 4. While age-wise trend in male group showed a slight decline in the third age interval, noticeable decrease in HDL-C serum concentration is apparent in female group in age level over 55 years (Fig 2). Values for total triglyceride serum concentrations are shown in Table 3. A higher mean value in male group compared to female group is seen with an increasing trend visible for both sexes with advancing age (Fig 1). In all ethnics groups triglyceride serum concentrations showed significantly higher level in male compared to female groups (Table 5).
Fig. 2.
Ethnic-wise (a) and age-wise (b) changes of serum concentrations for lipoproteins particles in the studied populations
Similar cascade of changes are observed for VLDL-C to those seen for total triglyceride concentrations in different ethnics and age groups (Tables 4, and 5). The results of statistical comparative analysis between the obtained values in this study with similar values reported for different populations are summarized in Table 6.
The contribution of various traditional and new risk factors is implicated in different reports [10] and [11]. Derangements in lipids and lipoproteins metabolism known to play a determining role in cardiovascular diseases [12]. Regional and ethnic variations [9] in lipids and lipoproteins serum concentrations necessitate a thorough local investigation in order to determine their relevant reference ranges for a particular population. Although the age and sex-wise distribution patterns for different analytes concentrations obtained in our project showed similar features to that published by other literatures [13] but a noticeable ethnic difference concerning HDL-C values was detected (p < 0.001) (Table 5). Comparative analysis between our data with other nations (Table 6) showed that in our male group, the total cholesterol level was lower than that reported for American [14] and Japanese [15] (p < 0.0001) with no significant difference with Chinese [16] and Indian [13] values (Table 6). Values obtained for total triglyceride in our trial for male group was lower than the American, Indian and Chinese populations (p < 0.001) and higher than that reported for Japanese populations (p < 0.001). Our values for HDL-C was lower than figures reported for other nations (p < 0.0001).
For female group, total cholesterol level was lower than the American, Japanese and Chinese populations (p < 0.001) (Table 6) with no difference with the Indian value (p = 0.95). The estimated value for total triglyceride in female group in our experiment was also lower than the values reported for American, Indian and Chinese (p < 0.001) and higher than the reported values for Japanese population (p < 0.001).
Serum level for HDL-C in our female cases was lower than the same figures reported for other nations (p < 0.001) with the exception of the Indian group (p = 0.17).
In conclusion our results clearly showed a significant disparity between the obtained results for our studied populations and the indices reported for other nations (Table 6). Also it is worth-reporting that an ethnic difference was detected concerning HDL-C in our populations (p < 0.01) (Table 5). These facts emphasizes the need for an epidemiological national survey taking into consideration the effects of variable such as age, sex and ethnicity in order to establish accurate reference ranges for lipids and lipoproteins particles to enable the clinicians to make appropriate clinical decisions.
References
- 1.Okrainec K, Banerjee DK, Eisenberg MJ. Coronary artery disease in the developing world. Am Heart J. 2004;148(1):7–15. doi: 10.1016/j.ahj.2003.11.027. [DOI] [PubMed] [Google Scholar]
- 2.Berenson GS, Srinivasan SR, Bao W, Newman WP, Tracy RE, Wattigney WA. Association between multiple cardiovascular risk factors and atherosclerosis in children and young adults. N Engl J Med. 1998;338(23):1650–1656. doi: 10.1056/NEJM199806043382302. [DOI] [PubMed] [Google Scholar]
- 3.McGill HC, Jr, McMahan CA, Malcom GT, Oalmann MC, Strong JP. Effects of serum lipoproteins and smoking on atherosclerosis in young men and women. Arterioscler Thromb Vasc Biol. 1997;17(1):95–106. doi: 10.1161/01.ATV.17.1.95. [DOI] [PubMed] [Google Scholar]
- 4.Stamler J, Daviglus ML, Garside DB, Dyer AR, Greenland P, Neaton JD. Relationship of baseline serum cholesterol levels in 3 large cohorts of younger men to long-term coronary, cardiovascular, and all-cause mortality and to longevity. JAMA. 2000;284(3):311–318. doi: 10.1001/jama.284.3.311. [DOI] [PubMed] [Google Scholar]
- 5.Strong JP, Malcom GT, McMahan CA, Tracy RE, Newman WP, III, Herderick EE, et al. Prevalence and extent of atherosclerosis in adolescents and young adults. JAMA. 1999;281(8):727–735. doi: 10.1001/jama.281.8.727. [DOI] [PubMed] [Google Scholar]
- 6.Interheart: Nine modifiable risk factors predict 90 % of Acute MI. European society of cardiology congress; 2004 [cited 2012 4 Feb 2012]. http://www.theheart.org.
- 7.Hajat C, Tilling K, Stewart JA, Lemic-Stojcevic N, Wolfe CDA. Ethnic differences in risk factors for ischemic stroke. Stroke. 2004;35(7):1562–1567. doi: 10.1161/01.STR.0000131903.04708.b8. [DOI] [PubMed] [Google Scholar]
- 8.Yusuf S, Hawken S, Ôunpuu S, Dans T, Avezum A, Lanas F, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the interheart study): case-control study. The Lancet. 2004;364(9438):937–952. doi: 10.1016/S0140-6736(04)17018-9. [DOI] [PubMed] [Google Scholar]
- 9.Yusuf S, Reddy S, Ounpuu S, Anand S. Global burden of cardiovascular diseases: part II: variations in cardiovascular disease by specific ethnic groups and geographic regions and prevention strategies. Circulation. 2001;104(23):2855. doi: 10.1161/hc4701.099488. [DOI] [PubMed] [Google Scholar]
- 10.Eng HS, Yean LC, Das S, Letchmi Santhna Y, Bakar Rohayu A, Hung J, et al. Anxiety and depression in patients with coronary heart disease: a study in a tertiary hospital. Iran J Med Sci. 2011;36(3):201–206. [PMC free article] [PubMed] [Google Scholar]
- 11.Schwandt P, Geiß HC, Ritter MM, Üblacker C, Parhofer KG, Otto C, et al. The prevention education program (PEP). A prospective study of the efficacy of family-oriented life style modification in the reduction of cardiovascular risk and disease: design and baseline data. J Clin Epidemiol. 1999;52(8):791–800. doi: 10.1016/S0895-4356(99)00068-2. [DOI] [PubMed] [Google Scholar]
- 12.Haas GM, Parhofer KG, Schwandt P. Prevalence of cardiovascular disease risk factors in migrants participating in the PEP family heart study, nuremberg. Int J Prev Med. 2010;1(1):19. [PMC free article] [PubMed] [Google Scholar]
- 13.Malati T, Mahesh MRU. Reference intervals for serum total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, Lp (a), apolipoprotein A-I, A-II, B, C-II, C-III, and E in healthy South Indians from Andhra Pradesh. Indian J Clin Biochem. 2009;24(4):343–355. doi: 10.1007/s12291-009-0063-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Fulwood R, Kalsbeek W, B r. National Center for Health Statistics, total serum cholesterol levels of adults 20–74 years of age; United States, 1976–80 Vital and Health Statistics. Public Health Service, Washington U.S. Government Printing Office, May 1986; Report No.: DHHS Pub No (PHS) 86-1686.
- 15.Noma A, Hata Y, Goto Y. Quantization of serum apolipoprotein AI, A-II, B, C-II, C-III and E in healthy Japanese by turbidimetric immunoassay: reference values, and age-and sex-related differences. Clin Chim Acta. 1991;199(2):147–157. doi: 10.1016/0009-8981(91)90106-M. [DOI] [PubMed] [Google Scholar]
- 16.Li Z, Yang R, Xu G, Xia T. Serum lipid concentrations and prevalence of dyslipidemia in a large professional population in Beijing. Clin Chem. 2005;51(1):144–150. doi: 10.1373/clinchem.2004.038646. [DOI] [PubMed] [Google Scholar]