Prevalence, pattern and clinical correlates of dyslipidemia among cardiology out patients in three reference hospitals of Yaounde
Prévalence et facteurs associés des dyslipidémies chez les patients en consultation externe de cardiologie dans trois hôpitaux de référence à Yaoundé.
BOOMBHI J 1, 2 , TCHAPMI D1, AMA Moor VJ1, 3, HAMADOU B 1, MENANGA AP 1,2 , KINGUE S1, 2
RESUME
Contexte: Les maladies cardio-vasculaires (MCV) sont une cause majeure de morbidité et de mortalité dans les pays développés et ceux en voie de développement. La dyslipidémie est un facteur de risque modifiable majeur de l'athérosclérose et des maladies cardio-vasculaires. Au Cameroun, peu d'études ont été menées pour évaluer les anomalies lipidiques. Le but de cette étude était de déterminer la prévalence et les facteurs associés à la dyslipidémie chez les patients vu en consultation externe de cardiologie à Yaoundé, au Cameroun.
Méthodes: Nous avions mené une étude transversale multicentrique du 5 décembre 2016 au 10 mai 2017 dans les services de consultation externe de cardiologie de trois hôpitaux de référence à Yaoundé, à savoir: l'Hôpital Général (HGY), l'Hôpital Central (HCY) et le Centre Hospitalier Universitaire de Yaoundé (CHUY). Nous avions recruté des patients qui venaient pour leur suivi régulier et qui ont donné leur consentement. La dyslipidémie a été définie par la présence d’au moins un paramètre anormal du profil lipidique. L'échantillonnage a été consécutif et l'analyse des données a été réalisée à l'aide du logiciel IBM SPSS 23.0.
Résultats: Au total, 505 patients ont été inclus dans notre étude. L'âge moyen des participants était de 55,7 ± 11,8 ans (étendue 28 à 98 ans). La prévalence de la dyslipidémie était de 65,4%. L'anomalie lipidique la plus fréquente était l’hypercholestérolémie totale (CT) (47,3%), suivie de l’hypercholestérolémie LDL (LDL-C) (41,6%), de l’hypocholestérolémie HDL (HDL-C) (20,7%) et enfin, l’hypertriglycéridémie (TG) (17,7%). La dyslipidémie était associée de façon significative au sexe masculin (p<0.001), à l’âge avancé (p=0,038), au diabète (p=0,002), au tabagisme (p=0,033) et à l'obésité (p=0,013). Nous avons aussi trouvé une corrélation faible mais significative entre le taux de triglycérides et le ratio taille-hanches (r = 0,2, p <0,001)
Conclusion: La prévalence de la dyslipidémie est élevée parmi les patients reçus en consultation externe de Cardiologie. Les troubles les plus courants étant un taux élevé de Cholestérol Total et de LDL-Cholestérol.
MOTS CLES
Dyslipidémie, facteurs associés, Yaoundé.
SUMMARY
Background: Cardiovascular Diseases (CVD) are a major cause of morbidity and mortality in both developed and developing countries. Dyslipidemia is a major modifiable cardiovascular risk factor for atherosclerosis and CVDs.In Cameroon few studies have been conducted to evaluate lipid abnormalities.The purpose of this study was to determine the prevalence, pattern and clinical correlates of dyslipidemia in patients attending cardiology outpatient consultation in a hospital setting in Yaoundé, Cameroon.
Methods: We conducted a cross sectional study from 5th December 2016 to 10th May 2017at the outpatient cardiology unit of three reference hospitals of Yaoundé, namely: General Hospital (YGH), Central Hospital (YCH) and the University Teaching Hospital of Yaoundé (UTHY).We recruited patients who came for their regular follow up and who gave their consent. Dyslipidemia was defined as at least one raised lipid profile parameter. Sampling was consecutive, and data analysis was done using the software IBM SPSS 23.0.
Results: A total of 505 respondents were enrolled in our study. The mean age of the participants was 55.7±11.8 (range 28 - 98 years). The prevalence of dyslipidemia was 65.4%. The most common lipid abnormality was high Total Cholesterol [TC] (47.3%), followed by high Low Density Lipoprotein Cholesterol [LDL-C] (41.6%), low High Density Lipoprotein Cholesterol, [HDL-C] (20.7%) and finally high triglycerides [TG] (17.7%). Dyslipidemia was found to be independently associated with male sex(p<0.001), old age(p=0,038), diabetes(p=0,002), smoking(p=0,033) and obesity(p=0,013). There was a weak but significant correlation between triglycerides and waist-hip ratio (r = 0.2, p < 0.001)
Conclusion: The prevalence of dyslipidemia is high in our Cardiology hospital setting, with the most common disorders being high TC and high LDL-C.
KEY WORDS
Dyslipidemia, associated factors, Yaoundé.
1 .Faculty of Medicine and Biomedical Sciences
2 .Yaounde General Hospital
Adresse pour correspondance
Dr Jérôme BOOMBHI
Faculty of Medicine and Biomedical Sciences
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BACKGROUND
Cardiovascular Diseases (CVD) are the leading cause of premature morbidity and mortality worldwide[1]. They have reached epidemic proportions in developing countries in recent decades due to the rising prevalence of risk factors of cardiovascular diseases owing to westernisation and urbanisation [2,3]. An estimated 17.5 million people died from CVDs in 2015, representing 31% of all global deaths. Most cardiovascular diseases can be prevented by addressing behavioural risk factors such as tobacco use, unhealthy diet and obesity, physical inactivity and harmful use of alcohol [4,5].
Lipid disorders are a major cause of cardiovascular diseases[6]. High serum cholesterol accounts for a third of all cardiovascular diseases (CVD) and the prevalence of lipid abnormalities has shown a steady rise in all countries over the years[7]. Lipid abnormalities are more common in people with diabetes mellitus (DM) and systemic hypertension, in whom the process of atherosclerosis is more aggressive and rapid, putting them at a higher risk for CVDs. Also, the three conditions: dyslipidemia, diabetes mellitus and hypertension tend to coexist in certain individuals, especially in obese subjects[8].
Like other developing countries, the Cameroonian population is experiencing unhealthy lifestyle changes. The country is undergoing social and economic changes, which are resulting in increased urbanization with a potentially negative impact on health-related behaviours. Between 1994 and 2003, the prevalence of hypertension in urbal and rural Cameroon increased by 2- to 5-fold[9].Kingue et al. in 2015 estimated the prevalence of hypertension at 29.7% in urban areas of Cameroon, with a very low awareness rate (14.1%)[10]. One of the earliest studies done on dyslipidemia in Cameroon was by Youmbissi et al[11]. They studied lipid abnormalities in patients with chronic kidney disease (CKD) and found a high atherogenic index in 61% of the participants. A recent hospital based study done in Yaoundé Teaching Hospital in patients with cardiovascular risk and diseases found higher prevalence of low HDL-C and high TG[12]. This study aimed to evaluate the lipid profile of patients seen in cardiology outpatient unit. It will add to the existing knowledge on the subject and increase awareness concerning lipid disorders in our patients.
MATERIELS AND METHODS
This was a cross sectional hospital-based study, conducted from the 5th December 2016 to 10th May 2017 in the outpatient cardiology unit in 3 reference hospitals of Yaounde, namely: Yaounde General Hospital (YGH), Yaounde Central Hospital (YCH) and the University Teaching Hospital of Yaounde (UTHY).Patients who came for routine medical visits to the cardiologist and gave their consent were included. We excluded pregnant women, patient less than 18 years old and patients who were admitted to the ward.
The Cochran’s formula was used to calculate a minimum sample size of 369 participants, assuming an error margin of 5%, a confidence interval of 95% and a prevalence of dyslipidemia of 60%. The prevalence was obtained from a study done in Ghana on lipid abnormalities among hospital attendants in an outpatient clinic in Kumasi [8]. Sampling was consecutive.
A pre-established questionnaire was administered to collect data on socio-demographic characteristics, lifestyle and past medical history. A physical examination was done and anthropometric parameters were measured and recorded.
Anthropometric measurements of height, weight, waist and hip circumferences were measured by Level 2 Criteria anthropometrists according to the standard procedures described by the International Society for the advancement of Kinanthropometry: ISAK[13].
The following definitions were adopted for the study:
Current smoker was considered as someone who reported smoking or who had stopped for less than one year[14].
Unhealthy diet was defined as absence of fresh fruits and cooked vegetables in the daily diet.
Physically active individuals were defined as those who do at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity aerobic physical activity throughout the week[15].
Hypertension was considered present if any of the following conditions were met: patient diagnosed in a health facility and/or reported use of a medication for hypertension [16].
Diabetes was considered present if any of the following conditions were met: patient diagnosed in a health facility and/or reported use of a medication for diabetes mellitus [17].
Obesity if Body Mass Index (BMI) ≥30 kg/m2[18].
Abdominal obesity was waist circumference greater than 102 cm in men and 88 cm in women[19].
Waist-to-hip ratio (WHR) was considered high if ≥0.90 cm for men or ≥0.85 cm for women[18].
TC, LDL-C. HDL-C and TG levels were classified on the basis of the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) as follows: High TC if , low HDL-C if , High LDL-C if , High TG if . Dyslipidemia was considered present if any one of the above lipid parameters were abnormal[19].
Atherogenic index (AI) was defined as LDL-C/HDL-C. High atherogenic index was defined as AI greater than or equal to 5[20].
Atherogenic Index of Plasma (AIP) was calculated according to the formula: . AIP was considered high if it was above 0.24[21].
We used the Cochran’s formula to calculate the minimum sample size[22]. We took an error margin of 5%, a confidence interval of 95% and a prevalence of 60%; we obtained a minimum sample size of 369 participants.
DATA ANALYSIS
Complete data were introduced on a data entry forms. All data were analysed using IBM SPSS version 23.0. Results were presented as mean with standard deviation, minima and maxima for quantitative variables; or as median and interquartile range when the distribution was skewed. We calculated frequencies and proportions for qualitative variables.
Association between dyslipidemia and the other study variables was determined using the Chi square test. The degree of association was determined using the Odd’s ratio with a confidence interval at 95%. For quantitative variables, association with dyslipidemia was determined by comparing the means with the Student t test or the medians with the Mann-withney U test. Correlations were done with the pearson’s or spearman correlation test. A p-value <0.05 was considered statistically significant.
Multivariate regression analysis was also done to reduce the effect of confounders with TC, TG, HDL and LDL as the outcome variables.
RESULTS
Characteristics of the study population
In total, 505 patients were enrolled in the study. There were261(52%) males. The mean age of the participants was years (range years). The modal group was the age range years containing 33.3% of individuals. Table I shows the characteristics of study participants by gender.
Height, weight, waist circumference, waist-hip ratio and all the lipoprotein ratios were significantly higher in men than in women. On the other hand, BMI, hip circumference, TC, HDL-C was significantly higher in women. There was no significant difference in the level of LDL-C and TG.
Prevalence of dyslipidemia
The overall prevalence of dyslipidemia (at least one abnormal lipid parameter) in our study population was (95% CI: ).Table II shows the prevalence of abnormal lipid values and lipoprotein ratios.
High TC (47.3%), high LDL-C (41.6%) and low HDL-C (20.7%) were the most frequent lipid abnormalities. About half of the participants were at risk of CVDs according to their AIP.
Table 3 shows the pattern of dyslipidemia by clinical group. This pattern was similar in all the groups, with the most prevalent abnormality being high TC, followed by high LDL-C. People with diabetes (diabetes only and diabetes + hypertension groups) had significantly lower HDL and higher TG (p<0.05). There was no significant difference in the prevalence of high TC and LDL-C amongst the clinical groups.
The variation of lipoprotein ratios with number of risk factors is shown in Table IV. The risk factors considered here were: hypertension, diabetes, tobacco smoking and obesity. There is an increase in values of all lipoprotein ratios, with increasing number of risk factors; hence, an increase risk for CVDs. The ratios TG/HDL-C and AIP increased significantly.
Factors associated with dyslipidemia
After adjusting for independent variables in multivariate regression analysis, low HDL-C remained associated with male sex (p<0.001) and diabetes (p=0.002); high LDL-C remained associated with obesity (p=0.013); high TG remained associated with age≥ 40 (p=0.038), smoking (p=0.033) and diabetes (p=0.019).
Table 5 shows the correlation between lipid parameters and some variables.
There were significant negative correlations between HDL-C and weight, height, waist circumference and waist-hip ratio. TG correlated positively with age, waist-circumference and waist-hip ratio. No significant correlation was found within the other lipid parameters. The strongest correlation was between TG level and waist-hip ratio ( =0.2, p<0.001).
DISCUSSION
Prevalence of dyslipidemia
Our study was conducted in cardiology hospital setting. Dyslipidemia was defined as at least one raised lipid profile parameter.
We found a prevalence of dyslipidemia was 65.4% in our study population. Such high prevalence increases the risk of atherosclerosis and Coronary Artery Diseases (CAD) in these patients. This high prevalence can be explained by the fact that we recruited patients in the cardiology outpatient unit. Also, the prevalence of high TC, LDL-C, TG and low HDL-C all increased with age, then declined. With the highest prevalence of all the dyslipidemia in the age range 55 – 64 years. A similar pattern was found by Sun et al. in rural Chinese population [23].
The most common lipid abnormality was high TC (47.3%) followed by high LDL-C. this was similar to the findings of Youmbissi et al in Cameroon [11], Micah et Nkum in Ghana[8] and Doupa et al in 2014 in Senegal[24].
Lipoprotein ratios are indices developed to quantify the atherogenicity of lipid profile. AIP has been shown to be superior in the evaluation of cardiovascular risk compared to the conventional lipoprotein ratios[21]. In our study, 5.4% had high LDL-C/HDL-C, which is similar to that found by Adeseye et al. who studied the dyslipidemia in newly diagnosed hypertensive patients in Nigeria[20].
Clinical group
Since diabetic patients have a pattern of lipid abnormalities known as diabetic dyslipidemia, we separated the patients into 3 groups for a comparative analysis, namely: people with diabetes only, hypertension only and diabetes with hypertension. There was a significant difference in prevalence of low HDL-C and high TG among the groups. Patients with diabetes tend to have lower HDL-C and higher TG and had the highest prevalence of dyslipidemia (72%). Jisieike-Onuigbo et al. in Nigeria studied lipid abnormalities in patients with diabetes mellitus found a similar pattern [25].
Number of cardiovascular risk factors
Cardiovascular risk factors considered were: hypertension, obesity, diabetes and current tobacco smoking. There was a significant increase in the prevalence of dyslipidemia and low HDL-C (p<0.05) with increasing number of risk factors. This can be explained by the fact that all these risk factors are linked and each are independent risk factors for dyslipidemia. So patients with many risk factors are prone to have a poor lipid profile.
Factors associated with dyslipidemia
After controlling for various confounding variables in multivariate analysis, the male sex and diabetes were associated with low HDL-C. Obesity was independently associated with high LDL-C. Finally, age, tobacco smoking and diabetes were associated with high TG.
Age: Longitudinal studies have shown that total cholesterol levels increase in males after the onset of puberty until age 50. Followed by a plateau until age 70, with the serum cholesterol concentration then falling slightly. The other lipid parameters also follow the same pattern[26]. In our study, those aged 40yrs and above had greater odds [p=0.038, AOR 3.6(1.1-12.1)] of having high TG. Osuji et al[27] and Yu et al[28] had similar findings in hypertensive adults.
Sex: Low HDL-C was independently associated with sex (p<0.001) within dividuals of the male sex having lower HDL values[AOR 3.9(2.2-7.0)]. Women are known to have higher HDL than men, which is in part due to estrogens which favour HDL-C synthesis[29] and some studies have shown that synthetic estrogen administration increase HDL levels[30].
Diabetes: Diabetic dyslipidemia refers to the triad of raised triglycerides, reduced HDL-C and excess small dense LDL particles in diabetic patients[31]. In our study, diabetes was significantly associated with low HDL and high TG. Micah et Nkum in Ghana [8] and Yu et al. in China [28] found similar associations.
Obesity: Obesity is in a constant rise in all countries in the world[32]. It was very frequent in our study population and was associated with high LDL-C [p=0.017, AOR 1.6(1.08-2.28)]. Osuji et al found an association of BMI with TG but not with LDL-C[27].
Smoking: Smoking is a major cardiovascular risk factor. In our study sample, many had quit smoking after being diagnosed of diabetes and hypertension. Smokers had 3 time higher risk of having high TG (p=0.033, AOR 3.4(1.1-10.4)) than non-smokers. Yu et al. found an independent association of current tobacco smoking with high TG and low HDL-C[28].
On bivariate analysis, waist circumference had a positive correlation with TG and all lipoprotein ratios, and a negative correlation with HDL-C. This can’t be used to draw conclusions, but it shows the importance of waist circumference in predicting cardiovascular risk.
Our study has some limitations: The major limitation is the cross-sectional design which reflects only associations between dyslipidemia and risk factors. Secondly, it is a hospital based study done in the cardiology unit so the prevalence of dyslipidemia is very high and does not reflect the prevalence in the general population.
CONCLUSION
The results of this study show that the prevalence of dyslipidemia among cardiology outpatients is high (65.4%), especially in patients with diabetes. The most common lipid abnormality was high TC (47.3%), followed by high LDL-C (41.6%), low HDL-C (20.17%) and high TG (17.7). There was an increase in the prevalence of dyslipidemia, low HDL-C and atherogenic indices with increasing number of cardiovascular risk factors. Sex, diabetes, alcohol, smoking, increasing age, menopause and obesity were independently associated with dyslipidemia.
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Figure 1: Linear correlation of AIP with waist circumference
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