The burden of hypertension and its associated factors among adults in Ruvuma, Southern Tanzania

Author(s): Jacqueline M. Mwita (1), Helmut A. Nyawale (2) and Fabian P. Mghanga (1)

1 Department of Internal Medicine, Faculty of Medicine, Archbishop James University College, Songea, Tanzania

2 Department of Community Medicine, Faculty of Medicine, Archbishop James University College, Songea, Tanzania

 

Correspondence: Fabian P. Mghanga, [email protected]

Citation:  Mwita et al, The burden of hypertension and its associated factors among adults in Ruvuma, Southern Tanzania. South Sudan Medical Journal 2020; 13(1):12-18 © 2020 The Author (s)  License: This is an open access article under CC BY-NC-ND

Submitted: September 2019 Accepted: December 2019 Published: February 2020

Abstract

Introduction: The prevalence of non-communicable diseases, and hypertension in particular, has been increasing.

Objective: To determine the prevalence and associated factors for hypertension among adults in Ruvuma, Southern Tanzania.

Methods: A cross-sectional study was conducted from September to October 2017; 802 patients were recruited, and data were collected on demographic, behavioural and clinical characteristics, and blood pressure, which were analysed using SPSS version 24.0. Associations and statistical significance were calculated using Odds ratio at 95% CI, and p-values of <0.05 were considered statistically significant.

Results: Overall, prevalence of hypertension (systolic blood pressure ≥140 and/or diastolic blood pressure ≥90 mm Hg, or known hypertensive patient on treatment) was 20.4% (21.4% and 19.5% in women and men, respectively) and that of pre-hypertension was 35.9%. Hypertension was associated with increasing age (p=0.01), excessive salt consumption (p<0.0001), and history of hypercholesterolemia (p<0.0001).

Conclusions: The prevalence of hypertension and pre-hypertension are relatively high. Intervention measures to prevent and control the disease are mandatory to prevent its progression and reduce morbidity and mortality.

Keywords: Hypertension; pre-hypertension; associated factors; prevalence

 

Introduction

The burden of non-communicable diseases is increasing in developing countries. [1,2] The World Health Organization estimates that by 2030, non-communicable diseases may cause up to46 % of deaths in sub-Saharan Africa. [2] Hypertension is a major modifiable risk factor for cardiovascular disease (CVD) and premature mortality.[3] Sub-Saharan Africa has more than 75 million hypertensive individuals and by 2025 it is estimated that about 125.5 million people will be affected.[4] The prevalence of hypertension varies between and within countries [5], in Tanzania, it varies from 16.4% in the west [6] to 28.0% in the north.[7]

The lifestyles of populations have changed with greater urbanization and economic growth. Many people exercise]7] less than previously while diets are often lower in fibre, but higher in salt, fat and calories. [8,9]

Little is known about the magnitude and determinants of hypertension in Southern Tanzania.

Objective

The objective of this study was to determine the burden of hypertension and assess associated factors among adults visiting the outpatient unit of a tertiary level health facility in Ruvuma, Tanzania.

Method

This cross-sectional study was conducted from September to October 2017 at Songea Regional Referral Hospital. A total of 802 patients who met the inclusion criteria were recruited from those attending the outpatient department. Inclusion criteria were: age 18-64 years, resident in the study area and consent to participate. Data on socio-demographic characteristics and risk factors for hypertension were collected by questionnaire.

All patients underwent physical examination. Body weight, height, hip and waist circumferences were measured, and the mean of two blood pressure (BP) records were obtained. The participant was regarded hypertensive if the systolic BP was >140 mmHg or diastolic BP was >90 mmHg or had reported regular use of antihypertensive drugs. All patients were classified as normotensive (systolic blood pressure (SBP) ≤120mmHg and diastolic blood pressure (DBP)<80mmHg), pre-hypertensive (SBP 120–139 and DBP 80–89mmHg), hypertension stage 1 (SBP 140–159 mmHg and DBP 90–99mmHg) or hypertension stage 2 (SBP≥160mmHg and DBP ≥100mmHg).[3]

The body-mass index (BMI) was calculated and patients classified as underweight (< 18.5 kg/m2), normal weight (≥ 18.5-24.9 kg/m2), overweight (≥ 25-29.9 kg/m2) or obese (≥ 30 kg/m2).

Recommended salt intake per day was defined as 6g or less while excessive salt intake was defined as> 6g (about one-teaspoonful) a day. For physical activity, patients were grouped: (1) vigorous physical activity, (2) moderate physical activity, (3) insufficient physical activity to meet vigorous or moderate levels, and (4) no physical activity.

Waist and hip circumferences were measured using flexible tape measure just above the iliac crest and at the maximum circumference of the hip, respectively. Waist-to-hip ratios of>1.0 for males and >0.85 for females were considered as abdominal obesity.

The study protocol was approved by the Internal Ethical Committee of Archbishop James University College. Permission to conduct the study was obtained from local and hospital authorities. Individual informed consent was obtained from patients

Statistical analyses were done using Statistical Package for Social Sciences version 24.0 (SPSS Inc., Chicago, IL, USA). Continuous data were expressed as means ± standard deviation (SD) and categorical data as percentages. Two-tailed Fisher’s exact tests were used to assess the associations between different variables. Logistic regression analyses were done to assess predictors of hypertension. A p-value of <0.05 was considered statistically significant.

Results

A total of 802 patients were enrolled: 48.3% were females; 87% were aged above 35 years; the mean age was 52.4±13.8 years; 48.4% were married. Almost half (48.0%) had never consumed alcohol while 84.9% denied a history of smoking (Table 1).

A quarter (24.2%) reported excessive consumption of salt and 90.1% consumed fruits at least 1 - 3 days a week; 99.4% ate vegetables at least 1-3 times a week (Table 1). Above normal waist-to-hip ratios were found in 14.9% of males and 14.7% of females. The mean BMI was 19.5±3.8 kg/m2; 4.7% were classified as obese; 17.9% were classified as taking insufficient or no physical exercise (Table 1).

 

Table 1. Socio-demographic, behavioural and clinical characteristics

Characteristics

n (%)

Sex

 

    Males

415(51.7)

    Females

387(48.3)

Age (years)

 

    18 – 34

102(12.7)

    35 – 44

161(20.1)

    45 – 54

127(15.8)

    55 – 64

234(29.2)

    65+

178(22.2)

    Mean ± SD

52.4±13.8

Marital status

 

    Married

388(48.4)

    Cohabiting

68(8.5)

    Single

132(16.5)

    Widowed

172(21.4)

     Divorced

42(5.2)

Residence

 

    Urban and semi-urban

491(61.2)

    Rural

311(38.8)

Education level

 

    Informal

 50(6.2)

    Primary

500(62.3)

    Secondary

 221(27.6)

    Tertiary

 31(3.9)

Occupation

 

    Peasant

423(52.7)

    Employed

214(26.7)

    Business person

113(14.1)

    Others

52(6.5)

Waist-to-hip ratio

 

Men

 

    ≤ 0.95

94(22.7)

    0.96 – 0.99

259(62.4)

    ≥1.00

62(14.9)

Women

 

    ≤ 0.80

211(54.5)

    0.81 – 0.85

119(30.8)

    ≥ 0.86

57(14.7)

Body-mass index (kg/m2)

 

< 18.5

155(19.3)

    18.5 – 24.9

528(65.9)

    25 – 29.9 

81(10.1)

    ≥ 30

38(4.7)

    Mean ± SD

19.5±3.8

Smoking status

 

    Current smokers

52(6.5)

    Past smokers

69(8.6)

    Non-smokers

681(84.9)

Alcohol consumption

 

    Current consumer

143(17.8)

    Past consumer

274(34.2)

    Never consumed

385(48.0)

Physical activity

 

    Vigorous

433(54.0)

    Moderate

225(28.1)

    Insufficient

127(15.8)

    No activity

17(2.1)

Fruits consumption per week

 

    1 – 3 days

429(53.5)

    ≥4 days

294(36.6)

    Not at all

79(9.9)

Salt consumption

 

    Recommended or less

608(75.8)

    Excessive

194(24.2)

Consumption of vegetables per week

 

    1 – 3 days

158(19.7)

    ≥ 4 days

639(79.7)

    Not at all

5(0.6)

Family history of hypertension

117(14.6)

Use of oral contraceptives (females)

36(4.5)

History of diabetes mellitus

63(7.9)

History of hypercholesterolemia

22(2.7)

Suffered from renal failure

9(1.1)

Suffered from heart failure

56(7.0)

Suffered from stroke

8(1.0)

SD = Standard deviation 

Of the 802 patients, 164 (20.4%) were hypertensive: 132(16.4%) and 32(4.0%) in stages 1 and 2 respectively (Table 2).

 

Table 2. Distribution of patients according to blood pressure categories 

Variable

n

Normo-tensive (%)

Pre-hypertension (%)

Hypertension stage 1 (%)

Hypertension stage 2 (%)

Total hypertensive (%)

General population

802

42.7

36.9

16.4

4.0

20.4

    SBP ± SD

802

119.4±7.2

131.6±5.8

147.4±6.3

161.2±3.2

150.5±4.0

    DBP ± SD

802

76.2±5.9

83.1±3.5

93.5±1.7

101.5±2.6

94.6±1.5

Sex

 

 

 

 

 

 

    Male

415

43.3

37.2

14.3

5.2

19.5

    Female

387

38.5

41.1

15.8

5.6

21.4

Age (years)

 

 

 

 

 

 

    18 – 44

263

47.7

37.5

10.6

4.2

14.8

    45+

539

40.6

36.2

16.9

6.3

23.2

SBP =Systolic blood pressure; DBP= Diastolic blood pressure; SD= Standard deviation

 

Among females, 21.4% were hypertensive compared to 19.5% of men (p=0.54). Hypertension was also associated with alcohol consumption, insufficient or no physical activity, and history of hypercholesterolemia (Table 3).

 

Table 3. Prevalence of hypertension across socio-demographic, behavioural and clinical characteristics

Characteristics

n

Hypertension, n (%)

OR (95% CI)

p-value

Normotensive

Hypertensive

Sex

 

 

 

 

 

0.54

    Male

415

334(80.5)

81(19.5)

0.89(0.63 – 1.25)

    Female

387

304(79.6)

83(21.4)

Age (years)

 

 

 

 

 

0.01

 

    18 – 44

263

224(85.2)

39(14.8)

0.58(0.39 – 0.86)

    45+

539

414(76.8)

125(23.2)

Marital status

 

 

 

 

 

0.01

    Married

388

294(75.8)

94(24.2)

1.57(1.11 – 2.22)

    Not married

414

344(83.1)

70(16.9)

Education level

 

 

 

 

 

<0.0001

    ≤Primary level

 550

468(85.1) 

82(14.9)

0.36(0.26 – 0.52)

> Primary level

252

170(67.5)

82(32.5)

Occupation

 

 

 

 

 

<0.0001

    Self-employed*

588

490(83.3)

98(16.7)

0.45(0.31 – 0.64)

    Civil servants

214

148(69.2)

66(30.8)

Waist-to-hip ratio

 

 

 

 

 

Men

 

 

 

 

0.01(0.01 – 0.03)

 

<0.0001

 

    ≤ 0.99

353

325(92.1)

28(7.9)

    ≥1.00

62

9(14.5)

53(85.5)

Women

 

 

 

 

0.02(0.01 – 0.04)

 

 

<0.0001

 

    ≤ 0.85

330

296(89.7)

34(10.3)

    ≥ 0.86

57

8(14.0)

49(86.0)

Body-mass index (kg/m2)

 

 

 

 

 

0.96(0.60 – 1.55)

 

 

0.90

 

    ≤ 24.9

683

544(79.6)

139(20.4)

    ≥ 25

119

94(79.0)

25(21.0)

Ever or still smoking

 

 

 

 

 

0.79(0.48 – 1.31)

 

 

0.39

    Yes

121

100(82.4)

21(17.6)

    No

681

538(79.0)

143(21.0)

Ever or still consuming alcohol

 

 

 

 

 

0.66(0.47 – 0.94)

 

 

0.02

    Yes

417

345(82.7)

72(17.3)

    No

385

293(76.1)

92(23.9)

Physical activity

 

 

 

 

 

0.35(0.23 – 0.52)

 

 

<0.0001

 

 

    Vigorous or

    moderate

658

547(83.1)

111(16.9)

    Insufficient or no

    activity

144

91(63.2)

53(36.8)

Fruits consumption per week

 

 

 

 

 

1.11(0.61 – 1.99)

 

 

0.77

    At least 1-3 days

723

574(79.4)

149(20.6)

    None

79

64(81.0)

15(19.0)

Salt consumption

 

 

 

 

2.02(1.39 – 2.93)

 

<0.001

    Excessive

194

136(70.1)

58(29.9)

    Normal or minimal

608

502(82.6)

106(17.4)

Family history of hypertension

 

 

 

 

 

0.89(0.54 – 1.46)

 

 

0.71

    Yes

117

95(81.2)

22(18.8)

    No

685

543(79.3)

142(20.7)

Use of oral contraceptives (females)

 

 

 

 

 

 

0.94(0.40 – 2.18)

 

 

 

1.00

    Yes

36

29(80.6)

7(19.4)

    No

766

609(79.5)

157(20.5)

History of diabetes mellitus

 

 

 

 

 

0.72(0.36 – 1.44)

 

 

0.42

    Yes

63

53(84.1)

10(15.9)

    No

739

585(79.2)

154(20.8)

History of hypercholesterolaemia

 

 

 

 

 

11.39(4.38 – 29.60)

 

 

<0.0001

    Yes

22

6(27.3)

16(72.7)

    No

780

632(81.0)

148(19.0)

History of renal failure

 

 

 

 

 

1.96(0.49 – 7.93)

 

 

0.40

    Yes

9

6(66.7)

3(33.3)

    No

793

632(79.7)

161(20.3)

History of heart failure

 

 

 

 

 

1.07(0.55 – 2.07)

 

 

0.86

    Yes

56

44(78.6)

12(21.4)

    No

746

594(79.6)

152(20.4)

 

Note: Self-employed included businesspersons, peasants and others; civil servants included employees in both public and private sectors.

OR = Odds Ratio; CI= Confidence Interval; SD= Standard deviation

 

High BMI, smoking tobacco or using tobacco products, and coexisting history of diabetes mellitus were predictors of hypertension. Non-modifiable factors such as age and sex, and modifiable behaviours such as excessive alcohol and/or salt consumption and lack of adequate physical activity were not predictors of hypertension (Table 4).

 

Table 4. Logistic regression analysis of the selected risk factors for hypertension

Variable 

AOR (95% CI)

p-value

Sex

0.94(0.31 – 2.81)

0.91

 

Age (years)

0.64(0.18 – 2.21)

0.47

 

Marital status

1.46(0.48 – 4.39)

0.50

 

Education level

0.36(0.12 – 1.12)

0.08

 

Occupation

0.51(0.16 – 1.64)

0.27

 

Body-mass index

2.73(0.89 – 11.01)

0.04

 

Smoking

3.70(0.99 – 13.81)

0.03

 

Alcohol consumption

0.64(0.21 – 1.94)

0.43

 

Physical activity

0.46(0.13 – 1.58)

0.23

 

Salt consumption

1.62(0.48 – 5.45)

0.44

 

Family history of hypertension

2.78(0.78 – 9.89)

0.13

 

History of diabetes mellitus

5.36(1.33 – 21.68)

0.02

 

 

AOR = Adjusted Odds Ratio; CI = Confidence Interval.

 

Discussion

The proportion of hypertensive patients attending the outpatient department was 20.4%. This is lower than that reported in hospital-based studies in Ethiopia[10] and South Angola[11] but twice that in another Ethiopian study.[12] The result is slightly lower than in community-based studies within Tanzania[6,7]but slightly higher than in North West Tanzania[13] and southern Ethiopia.[14] The differences may reflect variations in the occurrence of medical conditions associated with hypertension and also variations in the numbers of urban and rural patients in the studies.[10, 11]

We observed a prevalence (36.9%) of pre-hypertension similar to an observation in North West Tanzania where the overall prevalence rate (8.0%) of hypertension was lower. [13] Our findings show the public health burden facing both rural and urban Tanzania. 

We observed an increase in the prevalence of hypertension asso­ciated with age consistent with findings worldwide [3,4,6, 15]. Several African studies have explored the association between gender and hypertension with varying findings. [14] We found the prevalence of hypertension was similar among males and females at 19.5% and 21.4% respectively agreeing with other reports. [10] The association with marital status was intriguing and needs further study to determine if this is a true association.

In this study, almost 15.0% of both male and female patients had higher than normal waist-to-hip-ratio: of these, 85.5% of males and 86.0% of females had high blood pressure. Furthermore, being overweight or obese was significantly associated with three times increased risk of hypertension), and this is consistent with findings reported in community-based studies in sub-Saharan Africa. [6,7,10]

It is a well-established that obesity is associated with accumulation of “bad” cholesterol in the blood vessels reducing the blood flow with consequent hypertension. Interplay of factors that include sodium retention and activation of the renin-angiotensin – aldosterone system tends to occur in obesity and additionally vessel wall inflammation and insulin resistance may promote changes in the vascular function resulting into hypertension.

In this study, a history of hypercholesterolemia was significantly associated with the occurrence of hypertension. Patients who gave a history of diabetes mellitus had a five times risk of developing hypertension. Similarly, having a history of smoking was associated with a four times increased risk of hypertension. On the contrary, alcohol consumption and family history of hypertension did not have significant risk of having hypertension. This surprising discrepancy might be due to the low frequency of individuals with these risk factors in the study population. Also, the judgment as to alcohol consumption by an individual is notoriously difficult.

This being a cross-sectional study precludes the determination of any causal-effect relationships between variables.  Another limitation is that our data were obtained from a single centre and may not represent the general population of southern Tanzania. The fact that blood pressure measurements were taken on a single day is a further limitation. Also, importantly, the study assessed only demographic, behavioural and physical measurements; due to resources limitations, we did not do biochemical investigations which may have added further useful data.

Conclusion

In this study, almost one-fifth of the study population was hypertensive and another one-third were pre-hypertensive indicating a serious silent public health problem. Being overweight or obese, smoking tobacco, and a history of diabetes mellitus were predictors of hypertension. We recommend the promotion of health education about healthier life styles focusing on modifiable risk factors for hypertension.

Competing interests: None

Sources of Fund: None received

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