Hypertension is now on the increase in Nigeria where adoption of western lifestyles and the stress of urbanization both of which are expected to increase the morbidity associated with unhealthy lifestyles are progressing [9]. According to some researchers, hypertension and dyslipidemia account for more than 80% of deaths and disability in low- and middle-income countries. The relationship between obesity and high blood pressure through the anthropometric indexes in both clinical and population studies have been confirmed among the Nigerian adults [10,11].

Framingham and other epidemiological surveys as well as experimental studies have shown that serum lipid abnormalities are not only associated with hypertension, it significantly increases the risk for cardiovascular disease and its complications. Fasae et al. [12] and Tekes-Manova et al. [13] reported that dyslipidemia is the second most prevalent cardiovascular risk factor. However, in order to address the menace of obesity and dyslipidemia which are the risk factors of hypertension in a country by appropriate policy studies from different regions of the country need to be examined. This review examines the extent that obesity and dyslipidemia influence on the prevalence of hypertension in Nigeria.

METHODS

This review includes studies published between 2010 and April 23, 2018. The search terms used are nutritional status and lipid profile of hypertensive adults in Nigeria. Having the search to start from 2010 is to give allowance to cover all the studies done in the six regions of Nigeria. Six studies were reviewed and each study comes from each geopolitical zone of Nigeria (Table 1). In order to eliminate difficulty in analysis, only surveys which used BMI to measure the nutritional status and which conducted the lipid profile of the hypertensive adults were selected. Though there were studies which measured the waist circumference and waist-hip ratio but BMI is used as a reference for this review. Obesity is defined as a body mass index (BMI) equal or greater than 30 kg/m² and overweight as BMI of 25 kg/m² and more but less than 30 kg/m² [14]. Serum lipid abnormalities were defined as elevated serum TC=5.2 mmol/l (=200 mg/dl); elevated serum LDL-c=3.37 mmol/l (130 mg/dl); elevated serum TG=1.7 mmol/l (=150 mg/dl); and low serum HDL-c<0.9 mmol/l (35 mg/dl) for males and <1.0 mmol/l (39 mg/dl) for females [10] Hypertension is defined by systolic blood pressure ≥ 140 mm Hg and diastolic blood pressure ≥ 90 mm Hg according to the European Society of Hypertension (ESH) and of the European Society of Cardiology (ESC) classification [15]. 

Criteria for the inclusion of articles are as follows:

1.     The study should only involve hypertensive adults in Nigeria.

2.     It should cut across at all the six geographical zones in Nigeria.

3.     The location of the study in Nigeria was stated.

4.     BMI was used to determine overweight and obesity

5.     Stratification of overweight and obesity was clearly spelt out.

6.     The survey should involve both males and females.

7.     The study should involve hypertensive adults whose lipid profiles were assessed.

In instances where more than one survey was obtained from a city or state, only the most recent study was included in the present research.

RESULTS

The search on the nutritional status and lipid profile of the hypertensive adults in Nigeria was conducted on 20 abstracts but only six abstracts met the inclusion criteria and full survey were obtained from the internet with the use of Google Scholar and PubMed as search engines. The mean BMI of the hypertensive patients attending the tertiary health centres in Nigeria ranges from 26.55 ± 4.17 kg/m² in Kano to 32.00 ± 8.20 kg/m² in Benin (Table 2).

The mean SBP of the hypertensive patients ranges from 143.32 ± 14.97 mm Hg in Kano to 163.3 ± 18.9 mm Hg in Nnewi. The mean DBP of the hypertensive patients ranges from 86.76 ± 9.24 mm Hg in Kano to 106 ± 16.4 mm Hg in Ilorin. The mean elevated Total Cholesterol ranges from 4.64 ± 1.02 mmol/L in Maiduguri to 4.89 ± 0.93 mmol/L in Ibadan. The mean elevated Triglyceride ranges from 0.96 ± 0.46 mmol/L in Benin to 2.93 ± 1.69 mmol/L in Ibadan. The mean elevated Low density lipoprotein ranges 3.00 ± 0.82 mmol/L in Nnewi to 3.1 ± 1.1 mmol/L in Kwara. The mean low High density lipoprotein ranges 1.06 ± 0.29 mmol/L in Maiduguri to 1.36 ± 1.26 mmol/L in Kano (Table 3).

On the association of lipid profile and hypertension, all hypertensive outpatients in the reviewed studies demonstrated elevated mean serum total cholesterol except the patients in Benin. Positive correlation was observed between raised blood pressure and elevated serum total cholesterol and lower high density lipoprotein in the cross sectional study conducted among hypertensive outpatients in Ibadan. Significant higher LDL-C was observed only among hypertensive patients in Ilorin, Nnewi, Kano and Benin. Elevated serum TG was found to be significantly higher among the hypertensive patients in Nnewi, Kano and Benin. Lower serum HDL-C was found to be prevalent among the hypertensive patients in Ibadan, Kano, Maiduguri and Kano. Only and Osuji et al. [6] and Talle et al. [16] reported a positive correlation between BMI and all lipid profile variables except HDL-C. Certain researchers found no correlation between BMI and any of the lipid profile variables. But, other studies did not observe the association between BMI and lipid profile variables.

Discussion

This review studied the nutritional status (based on Body Mass Index) and lipid profile of hypertensive patients attending the tertiary hospitals in Nigeria. Previous systematic review conducted by Chukwuonye et al. [17] reported the prevalence of overweight and obesity among Nigerian adults to be 20.3%-35.1% for overweight and 8.1%-22.2% for obesity. This review found prevalence of overweight among the hypertensive patients to be within 36.4%-51% and obesity to range from 17.0%-34.5%. It was observed that mean BMI among hypertensive outpatients in Nigeria ranges from 26.55 ± 4.17 kg/m2 to 32.00 ± 8.20 kg/m2. This confirms the reports of previous studies that many of the hypertensive patients attending Nigeria tertiary hospitals are still overweight and obese [10,18,19]. Prevalence of overweight and obesity among the hypertensive patients in Nigeria reveals that majority of them are suffering from diabetes and other metabolic disorders.

Positive correlation between hypertension and BMI was observed in the studies conducted by Osuji et al. [6] and Saidu et al. [20] in Nnewi and Kano. Maduka et al. [21] reported high prevalence of obesity among hypertensive patients in Maiduguri, whereas, others reported high prevalence of overweight among the hypertensive patients in Ibadan. In contrast, no correlation was found between hypertension and BMI among hypertensive patients in Benin and Ilorin [12,21] This review shows that relationship of hypertension with overweight and obesity is uncertain in South-south and North Central of Nigeria. Although, Idemudia [22] had earlier reported significant high BMI among the hypertensive patients compared to normotensive individuals. Study conducted by Gudlavalleti et al. [23] across different ethnic groups in Nigeria also affirmed that hypertension increased with BMI but BMI is independently associated with hypertension at p<0.001 and south-south had significant higher odds ratio of hypertension than other geopolitical zones in Nigeria.   

Previous systematic review conducted revealed that the prevalence of hypertension among adults in Nigeria ranges from 43.6% to 50.8%. This study found uncontrolled systolic blood pressure to range from Grade 1 hypertension (143.32 ± 14.97 mm Hg) to Grade 2 systolic hypertension (163.3 ± 18.9 mm Hg) and diastolic blood pressure ranges from high normal (86.76 ± 9.24 mm Hg) to Grade 3 diastolic blood pressure (106 ± 16.4 mm Hg) according to the classification of European Society of Hypertension and the European Society of Cardiology (ESH/ESC). Although, the mean systolic BP among the Nigerian hypertensive patients is lower than those in India, the mean diastolic BP of Nigerian hypertensive patients is higher than theirs [24].

Having hypertensive patients with significant high lipid profile in the reviewed studies confirms the result of previous studies conducted both in Nigeria and abroad which reported close association between raised blood pressure and dyslipidemia [25-27] show that Total cholesterol and the mean of serum LDL level were significantly higher in the hypertensive patients in Iran. Pyadala et al. [28] also reported a significantly higher TC, TG, LDL and very LDL in hypertensive subjects that visited teaching hospital in Sanga Reddy, India. However, hypertensive patients who have hyperlipidemia are at risk of developing diabetes and kidney disease [2]

LIMITATIONS OF THE STUDY

This review has limitations in some areas. Many of the studies reviewed used small sample size. Not all the studies measure the association between BMI and lipid profile, BMI and hypertension and lipid and hypertension. Many of the studies did not measure dietary intake and lifestyles which could be the risk factors of dyslipidemia, overweight, obesity and hypertension. These limitations could affect the generalizability of this review to the condition of hypertensive outpatients in Nigeria.

CONCLUSION

It becomes evident that hypertensive outpatients in Nigeria still demonstrate hypertension up to the isolated systolic hypertension. Overweight, obesity and dyslipidemia are the predictors of the high blood pressure in Nigeria. The association between hypertension and dyslipidemia is uncertain in some parts of Nigeria. Many of the hypertensive outpatients in Nigeria are suffering from other metabolic disorders along with hypertension which could be diabetes, renal diseases or both. The patients shows the tendency of suffering from cardiovascular diseases such as atherosclerosis, heart diseases and stroke later in future if appropriate measure is not put in place.

RECOMMENDATION

The physicians are encouraged to assess the obesity and dyslipidemia among their hypertensive patients, monitor the patients to weight loss and direct them to registered dietitians for dietary regime to monitor their dietary intake which could predispose them to hyperlipidemia. Government at all levels is encouraged to provide financial support in the diagnostic procedures of hypertension which could be costly for some hypertensive patients to do on their own. 

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  Table 1
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  Table 2
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  Table 3