A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfillment
of the requirements for the degree of Doctor of Philosophy
Johannesburg, 2014 / Background:
Individuals infected with the human immunodeficiency virus (HIV) are living longer due to effective
disease management with highly active antiretroviral therapy (HAART). International literature
suggest that mortality in people living with HIV and AIDS (PLWHA) is shifting to non-AIDS defining
diseases such as cardiovascular disease. It is suggested that PLWHA are at an increased risk for
developing ischemic heart disease (IHD) due to HIV mediated processes, traditional risk factors of
IHD and factors related to HAART exposure. In the South African context risk factors for IHD are
reported to be on the increase in the general population but published information regarding the
risk factors for IHD in PLWHA is limited. Human immunodeficiency virus infection is a significant
Sub-Saharan Africa challenge with 5.26 million people living in South Africa (SA) reported to be
infected with HIV. Only Swaziland, Lesotho and Botswana report higher prevalence rates of HIV
infection. Due to the high prevalence rate of HIV in SA, the reported increase in risk factors for IHD
in the general population and the suggested increased risk for IHD in PLWHA, screening these risk
factors in PLWHA in the South African context may be necessary. Innovative prevention strategies
for IHD are also required to manage the risk for IHD in PLWHA in SA due to the high prevalence
rate. A home-based education and pedometer walking programme could be such a strategy. The
aims of the research project were therefore firstly to screen selected risk factors for IHD in PLWHA
attending a primary care clinic and secondly to evaluate said individuals’ self-perception regarding
their risk of IHD. Lastly the project set out to determine the effects of an individualised education
and home-based pedometer walking programme on the risk of IHD as a potential prevention
management strategy for IHD in PLWHA.
Methodology:
The research project consisted of four studies divided into phase 1 (study 1, 2, 3) and phase 2
(study 4). The study aims, methods and data analysis approaches were:
Study 1: Aimed to screen a sample of PLWHA (on HAART) for physical activity and selected risk
factors of IHD using the Yamax SW200 pedometer and other appropriate methods respectively.
This study was an observational study and data analysis consisted of descriptive analysis and
reviewing associations with univariate logistic regression analysis. A p–value less than 0.05 was
considered statistically significant.
Study 2: Aimed to evaluate participants’ self-perception and behaviour in relation to the risk of IHD
using a semi-structured interview and card sort technique. This study was a qualitative study and
data analysis consisted of descriptive and conventional content analysis.
Study 3: Aimed to develop the education physical activity diary that was used in phase 2. The
methodological processes included a literature review, a review of the education material to be
included in the physical activity diary by an academic peer–review panel, review by a clinician
working with PLWHA and a sample of PLWHA. Following these activities the diary was constructed
and translated into isiZulu.
Study 4: Aimed to assess the effects of an education and home-based pedometer walking
programme on the risk factors of IHD in a sample of PLWHA (on HAART) with an increased risk for
IHD as determined in study 1. The study was a randomised controlled trial consisting of an
intervention and control group. Assessments were done at baseline, six and 12 months. Control
participants continued with standard clinic care and were phoned once a month for five months
during the baseline and six month interval. The intervention participants received a Yamax SW200
pedometer, an education physical activity diary, individualised walking programme and had once a
month face-to-face education sessions in the baseline to six month interval. Intervention
participants were instructed to continue with their physical activity modification programme during
the six to 12 months period. No contact was made with control or intervention participants during
this time. Intention-to-treat analysis was the primary approach for study 4. Data analysis consisted
of descriptive analysis (mean [±SD] and frequencies [percentages]) and randomisation to group
allocation was assessed using a two sample/ independent t-test or Wilcoxon rank–sum (Mann–
Whitney) for non-normally distributed continuous data. Categorical data were evaluated with the
Pearson Chi Square test. A p–value less than 0.05 was considered statistically significant. To
evaluate the effect of time on outcomes assessed, repeated measures ANOVA for within-group
changes were performed. To evaluate the effect of the programme on outcomes assessed,
repeated measures ANCOVA with baseline values as co-variates were performed to highlight the
between-group effect. To assess the associations between dependent variables and the time and
intervention/control interaction the pedometer data were log-transformed due to skewness. The
generalised estimation equation (GEE) and mixed effects model (MEM) approaches were used to
fit the univariate and multivariable models. The correlation structure selected was the
exchangeable option with the identity link function suitable for Gaussian data. The relationship
between high sensitivity C-reactive protein (hs-CRP) at baseline and evaluated risk factors for IHD
was assessed with the Pearson correlation coefficient and univariate logistic regression in MEM
respectively on log-transformed hs-CRP.
Results:
Study 1: Two hundred and five PLWHA (on HAART) were screened for selected risk factors for
IHD. The demographic characteristics of participants consisted of the following: mean age (38.2
[±9.5] years), gender (men [n=47; 22.9%] and women [n=158; 77.1%]), most participants had a
secondary educational level (n=95; 46.3%), were employed (n=115; 56.1%) and were supporting
dependents (n=158; 85.4%). The majority of participants perceived their general health as good
(n=120; 58.5%), but felt their body shape had changed in the last six months (n=123; 60%). This
was mostly due to a reported increase in weight (n=132; 64.4%). The mean time on HAART was
8.7 (±2.3) months, with the majority of participants being diagnosed as HIV positive between 2009
to 2011 (n=134; 66%). The majority of participants were on Lamivudine, Efavirenz and Tenofovir
(n=139; 67.8%) therapy with a mean CD4 count of 285.1 (±157) cells/mm3 and viral load of 12
513.2 (±59 710.6) copies/ml. The physical activity levels of participants were reduced with the
mean pedometer step count per day found to be 7 673.2 (±4 017.7) with men being more active
(10 076.3 [±4 885.6] steps per day) than women (6 993.3 [±3 462.6] steps per day). The majority of
study participants (n=150; 77%) took less than 10 000 steps per day. Taking less than 10 000
steps per day was related to waist circumference (WC) (odds ratio=1.04; 95% CI: 1.00–1.08;
p=0.03) when adjusted for age and gender. Eight participants (3.9%) participated in formal sporting
activities that were supervised and 123 participants (60%) tried to incorporate exercise into their
daily lives. The preferred activity method for exercise was walking (n=56; 45.5%) and running
(n=33; 26.8%). Perceived stress was moderately high with a mean Cohen’s Perceived Stress
score at 19.2 (±7.8) with women reporting higher levels of stress (20 [±7.1]) than men (16.9 [±9.1]).
A family history of IHD was low in participants (n=29; 14.2%) as well as a known diagnosis of
diabetes mellitus (n=1; 0.005%), hypertension (n=19; 9%) and current smoking status (n=33;
16.1%). The majority of participants reported not being able to consume fish weekly (n=114;
55.6%) and reported weekly consumption of fruit and vegetables (n=110; 53.7%). Few participants
were able to consume three to five vegetables and fruit combined per day (n=68; 33.2%). The
mean resting heart rate (RHR) of the sample was slightly elevated (82.7 [±11.4] bpm) with having a
RHR ≥ 80 bpm related to diastolic blood pressure (DBP) (odds ratio=1.07; 95% CI: 1.03–1.11;
p<0.00) and physical activity (odds ratio=0.99; 95% CI: 0.99–0.99; p=0.02) as adjusted for age and
gender. The sample as a whole was overweight with a mean body mass index (BMI) of 25.6 (±1.4)
kg/m2. Having a BMI ≥ 25 kg/m2 was related to systolic blood pressure (SBP) (odds ratio=1.07;
95% CI: 1.04–1.10; p<0.00), WC (odds ratio=1.34; 95% CI: 1.22–1.46; p<0.00), hip circumference
(odds ratio=1.53; 95% CI: 1.38–1.75; p<0.00) and CD4 count (odds ratio=1.00; 95% CI: 1.00–1.01;
p=0.01) as adjusted for age and gender.
Study 2: Thirty PLWHA (on HAART) were purposefully sampled according to the following criteria:
individuals had to be on HAART for six to 12 months, between the ages of 20 and 65 years and
ambulatory without an assistive device with no pre-existing history of cardiovascular disease,
mental illness, current acute infection, current pregnancy or breast-feeding women. The
demographic details of participants were as follows: median age 36.5 (31.8–45.0) years; women
(n=25; 83.3%) and men (n=5; 16.7%); the majority of participants (n=16; 53.3%) had a secondary
school education, were employed (n=17; 56.7%) and were supporting dependents (n=26; 86.7%).
Knowledge and understanding related to IHD, insight into own risk for IHD and health character in
the HIV context were identified as three prominent themes. An important finding that the study
highlighted was that participants did not perceive themselves to be at risk for IHD due to being
HIV+ or using HAART in any way. The majority of participants (n=15; 50%) did not perceive
themselves to be at risk for IHD due to reporting having adequate coping behaviour and living a
healthy lifestyle. Twelve (40%) participants did however perceive a risk for IHD due to physical
symptoms experienced and their behaviour consisting of a poor diet, elevated stress levels and
lack of exercise. Three (10%) participants were unsure concerning their risk for IHD in the future.
Study 3: A selection of pages from the education physical activity diary can be found in Appendix
31.
Study 4: Eighty four PLWHA (on HAART) participated in study 4.
The education and home-based walking programme implemented in study 4 was successful in
improving physical activity levels in both the control and intervention groups, as participants’
pedometer-determined step-count increased from baseline. The within-group change at six months
were statistically significant (p=0.03) for both groups but not so for the 12 month period (control
group [p=0.33] and intervention group [p=0.21]). It was however of clinical value in the intervention
group, due to the group exceeding the step count aim of the programme, that being 3 000 steps
above baseline at each assessment point. Translating the step count into time, would amount to
approximately 30 minutes of added walking per day. The group therefore reached the Public
Health recommendations for physical activity. Social support in the form of encouragement,
motivation and participation from friends and family was noted as important enablers that assisted
intervention participants to adhere to their programme.
No significant differences were observed in the sociodemographic profile, HIV related clinical
markers and antiretroviral therapy and IHD risk factors evaluated at baseline. The study highlighted
that inflammation (hs-CRP) was a significant risk factor for IHD in the study cohort due to mean
baseline values of 8.6 (±8.4) mg/l in the intervention and 5.4 (±6.5) mg/l in the control group.
Inflammation (hs-CRP) was related to perceived stress (Pearson correlation [r=0.23; p=0.03] and
MEM univariate logistic regression [log B=0.04; 95% CI: 0.0004– 0.08; p=0.03]), weight (Pearson
correlation [r=2.8; p=0.01] and MEM univariate logistic regression [log B=0.02; 95% CI: 0.01–0.04;
p=0.01]), BMI (Pearson correlation [r=0.35; p<0.00] and MEM univariate logistic regression [log
B=0.07; 95% CI: 0.03–0.12; p<0.00]), WC (Pearson correlation [r=0.28; p=0.01] and MEM
univariate logistic regression [log B=0.03; 95% CI: 0.06–0.36; p=0.01]) and hip circumference
(Pearson correlation [r=0.28; p=0.01] and MEM univariate logistic regression [log B=0.02; 95% CI:
0.01–0.04; p=0.01]). The risk for IHD according to Framingham Risk Score (FRS) calculation was
low as baseline FRS points were 3.3 (±6.5) points in the control group and 2.5 (±6.5) points in the
intervention group.
The education and home-based walking programme was effective in increasing physical function
capacity (six-minute walk test mean difference: 15.70 [±9.33] meters), reducing waist: hip ratio
(mean difference of -0.003 [±0.01] cm), reducing glucose level (mean difference of -0.12 [±0.09]
mmol/l) and increasing HDL (mean difference of 0.07 [±0.05] mmol/l) as evaluated during betweengroup
analysis.
The within-group analysis indicated that a significant reduction in SBP occurred in both groups at
the six months time period (control group: p=0.03 and intervention group: p<0.00). A slight
increase in BMI occurred in both groups at the six and 12 month period that were statistically
significant (p<0.00). A significant reduction in total cholesterol (p=0.04) and LDL (p<0.00) at the 12
month period were also noted in the control group.
The log-transformed univariate logistic regression model highlighted many associations between
the interaction (time and treatment: control or intervention group effect) and secondary outcomes
assessed. The inverse associations between perceived stress levels (p<0.00) and BMI (p=0.02)
with the six month time interval of the control and intervention groups compared to baseline control
findings were confirmed during multivariable analysis in the log-transformed GEE model.
Additionally an inverse association between perceived stress levels (p<0.00), BMI (p<0.00), LDL
(p=0.01) and triglycerides (TG) (p=0.01) at the six month time interval of the intervention group
compared to baseline control findings were confirmed in the multivariable analysis in the logtransformed
MEM model.
Conclusion:
This project showed that physical inactivity, elevated perceived stress levels, inadequate diet of
fruit, vegetable and fish intake, elevated RHR, increased BMI and raised hs-CRP were risk factors
for IHD in the study cohort. These risk factors screened indicated an elevated risk for IHD in the
future even though the FRS demonstrated a low risk for IHD. An IHD predictive model that
incorporate hs-CRP when evaluating risk for IHD and which has been validated for use in PLWHA
is therefore necessary to adequately evaluate the risk for IHD in this population. This is especially
of relevance in the South African context considering the prevalence of HIV infection in women and
the association of female gender with hs-CRP as indicated in the literature.
The project highlighted that an elevated stress level was a significant risk factor for IHD in the
study cohort and was also given as one reason why participants perceived themselves to be at risk
for IHD. The positive association between perceived stress and hs-CRP was also of value. The
stress lowering effect of the education and home-based pedometer walking programme was
therefore of significant importance as it could manage this risk factor. Additionally if stress declines
it could potentially also influence hs-CRP in the long term. The study therefore contributes to the
body of knowledge related to the effects of exercise on psychological parameters in PLWHA.
Additionally the project confirmed that an optimistic bias in individuals living with HIV is present
regarding their future possibility for developing IHD. Their perception for the risk for IHD did not
always align with the risk factors present as screened. This might be due to the fair application of
knowledge related to IHD when evaluating their risk for IHD. It also confirmed that education
strategies are needed to explain the risk factors for IHD and how HIV infection and HAART
influence these risk factors of IHD.
Lastly the project found that an education and individualised home-based pedometer walking
programme was able to influence physical activity levels positively and was successful in reducing
the risk of some factors for IHD in PLWHA at primary care level. Such a programme can be
implemented as an innovative method to manage risk factors for IHD in PLWHA by
physiotherapists especially in regions where physiotherapy numbers are low and HIV prevalence
high.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/17466 |
| Date | 21 April 2015 |
| Creators | Roos, Ronel |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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