Sex differences in physical activity among Ghanaian patients with sickle cell disease

Introduction Musculoskeletal pain and functional limitations experienced by patients with Sickle Cell Disease (SCD) impact their physical activity and social behaviour. Yet, we know little about physical activity behaviour in patients with SCD. The aim of this study was to investigate gender differences in physical activity, sedentary time and measures of fitness among Ghanaian adults with SCD. The study also determined the association between outcome variables in this population. Methods Patients with SCD attending a sickle cell clinic in a tertiary hospital in Accra, Ghana participated in this cross-sectional study. Physical activity, sedentary time, body composition, flexibility and cardiovascular endurance were assessed. Demographic data were also collected by self-report. Results Fifty three participants enrolled in the study. Of these, more than half were females (60.4%) and the average age of the participants was (M: 26.8, SD: 8.5 years). The total physical activity reported by the participants was different between males and females (t = 2.610, p = 0.012). However, there were no gender differences in sedentary time, body composition, flexibility and cardiovascular endurance. A moderately significant association was found between sedentary time and cardiovascular endurance (r = 0.437, p = 0.001). Conclusion The findings suggest that gender differences in physical activity are apparent in patients with SCD. Investigations into the mechanisms underpinning these differences are warranted. Additionally, longitudinal observations of objectively measured physical activity may be useful to validate these results in a larger sample.


Introduction
Physical activity is an important health-enhancing behaviour with established benefits in apparently healthy populations [1,2] and individuals with pathological conditions [3][4][5][6]. Despite these, physical inactivity and low cardiorespiratory fitness have become a global concern probably because of the relationship between physical inactivity and non-communicable diseases [7][8][9][10]. To design effective interventions to address physical inactivity in a particular group, accurate physical activity data on the relevant population is needed [11]. Therefore, it is prudent to measure physical activity levels and  [16][17][18] and is known to be more common within the Sub-Saharan Africa compared to other parts of the world [18]. In Ghana, SCD is linked to high rate of mortality and morbidity, with prevalence of about 1.6% [19]. It has been reported that 25-30% of the Ghanaian adults are carriers of the sickle cell trait and 2% of babies have SCD [20,21]. Notable complications associated with SCD include painful crisis, infection, acute chest syndrome, priapism, stroke, renal medullary cancer and splenic infarction [16,18,22]. Evidently both children and adults with SCD have lower quality of life and poor functional capacity compared to those without the disease [16,23]. Also, people with SCD are often stigmatized [20], which negatively impact their social behaviour. The numerous complications associated with SCD could be expected to have a negative impact on physical activity. Likewise, reduced physical activity may further worsen patients' risk for other noncommunicable diseases. To optimize the functional capacity of adults with SCD, a multidisciplinary management strategy that gives consideration to both medical and non-medical problems should be adopted. However, this would require better understanding of the impact of the disease on known health indicators such physical activity and fitness. Since physical activity predicts functional capacity and influences quality of life, deeper insight about the physical activity behaviour of patients with SCD is necessary. There is generally lack of information on physical activity among patients with SCD worldwide. To the authors' knowledge, no study has examined gender differences among patients with SCD. Therefore, the purpose of the study was to investigate gender differences in physical activity, sedentary behaviour, and aspects of physical fitness among Ghanaian adults with SCD. In addition, we examined the differences in outcome variables between patients with the haemoglobin SS and those with haemoglobin SC types of SCD. Associations between physical activity, sedentary time, body composition, flexibility and cardiovascular endurance were also determined. We hypothesized that male patients with SCD would exhibit higher physical activity and fitness than females.

Participants and setting
The participants of the study were patients who had been diagnosed as having SCD by a physician and were receiving medical treatment at the Ghana Institute of Clinical Genetics (Sickle Cell Clinic) of the Korle-Bu Teaching Hospital (KBTH) in Accra. Participants were included if they were aged 18-60 years, had been diagnosed as having SCD, and were willing to participate in the study. Individuals who had co-morbidities and physical impairments such as osteoarthritis that limited participation in assessment procedures were excluded. Also, patients who were in crisis and/or recovering from recent episodes of crisis were excluded. Each participant provided written informed consent before enrollment.

Procedure
All the participants were tested in a designated cubicle at the clinic.
All assessments were conducted over two visits by trained assessors (final year physiotherapy students) in the presence of a physician and nurse. On the first visit, anthropometric and demographic data were collected. Immediately after this, flexibility and cardiovascular endurance tests were administered. The participants were allowed 30 minutes rest between tests. On the second visit, the participant completed the physical activity questionnaire.

Anthropometric data
Height was assessed using a wall-mounted tape measure and weight was measured with a portable calibrated electronic scale. Body Mass Index (BMI) was computed by imputing the height and weight scores into the formula: Demographic data such as age, gender, level of education and marital status were collected by self-report.

The Sit-and-reach test
The sit-and-reach test (SRT) was used to measure flexibility. The test required participants to sit with their knees extended and the feet placed against a wooden box. They were instructed to place their right hand over the left and slowly reach forward as far as possible by sliding their hands along the box. The validity and reliability of the SRT have been previously reported [24][25][26][27]. The SRT was chosen because it is practical, less expensive and easy to administer. Three trials were conducted and the best score was used in the analysis.

The three minute step test
The three minute step test (TMST) was used to evaluate cardiovascular endurance. The TMST was performed in accordance with recommended protocol [28]. Each participant was required to step on and off a 12inch wooden step 24 times for 3 minutes. A metronome set at 96 beats per minutes was used to synchronise the participants' stepping cycle [29]. After the test (within 1 minute), the participant sat on a chair and their heart rate was measured by auscultation using a stethoscope. All the participants completed the test (100%) without any adverse complaints.

The Global Physical activity Questionnaire (GPAQ)
The Global physical activity questionnaire (GPAQ) was used to assess physical activity behavior [30]. The GPAQ is a 16-item scale that measures three major dimensions of physical activity; work, transport and recreational activities. The tool also evaluates sedentary behavior. Responses to the items of the questionnaire can be converted into component scores in metabolic equivalents (METs).
Component scores are then summed to produce total physical activity which represents one's physical activity behavior per week. The tool has acceptable psychometric properties and is reported to be suitable for monitoring physical activity in adult populations [31,32].

Statistical analysis
The Shapiro-Wilk test was used to check for normality of the data.
Descriptive data is presented as means, standard deviations and percentages. The independent sample t-test was used to determine mean differences of all continuous variables between males and females. Also, mean differences (of continuous variables) between patients with haemoglobin SS and those with haemoglobin SC were examined with the independent sample t-test. Since physical activity is related to physical fitness, we examined the relationship between physical activity, sedentary time, body composition and cardiovascular endurance using the Pearson's correlation coefficient.
All statistical analyses were performed using the SPSS software version 23.0 at a significance level of p<0.05.

Results
Description of Participants' characteristics. The descriptive characteristics of the participants are shown in respectively. Most of the participants (52.8%) were identified as having the haemoglobin SS type of SCD Table 1.

Comparisons of outcomes between males and females.
As shown in Table 2, there were significant differences in total physical activity (t = 2.610, p = 0.012), moderate work-related physical activity (t = 3.587, p = 0.001) and moderate-recreational physical activity (t = 3.045, p = 0.004) between males and females.
However, we found no statistically significant difference in sedentary time, flexibility, body composition and cardiovascular endurance between males and females Table 2.

Comparisons of outcomes between patients with haemoglobin SS and those with haemoglobin SC
We observed a significant difference in cardiovascular endurance (t = 2.640, p = 0.011) and body composition (t = -2.351, p = 0.023) between patients with haemoglobin SS and those with haemoglobin SC. There were no differences in physical activity, sedentary time and flexibility between the two patient groups Table 3.

Associations between physical activities, sedentary time, body composition, flexibility and cardiovascular endurance
With regard to the relationship between the measured variables, we observed a moderately significant relationship between cardiovascular endurance and sedentary time (r = 0.437, p = 0.001).
The relationship between cardiovascular endurance and any other variable was weak and non-significant Table 4.

Discussion
In this study, SCD was found to be more prevalent in females compared to males. We also observed that the number of patients with the haemoglobin SS were more than those with haemoglobin SC type of SCD in our sample. In general, there was a significant difference in total physical activity, moderate work-related activity and moderate recreational activity between males and females. The males reported higher total physical activity levels than the females.
In addition, there was a significant difference in cardiovascular endurance and body composition between patients with haemoglobin SS and those with haemoglobin. Finally, a moderately significant association was noted between cardiovascular endurance and sedentary time. Our finding that SCD is more common in females than males corroborates that of earlier research [23,33]. Research in the field has often reported higher prevalence of SCD in females compared to males. The observations about the haemoglobin SS being the most common form of SCD in this population is also well supported in the literature [23].  What is known about this topic  Patients with SCD have reduced capacity to perform everyday activity tasks compared to their healthy peers;

Conclusion
 SCD is more common in females than males.

What this study adds
 This is the first study to report on physical activity behavior in patients with SCD;  Gender differences in physical activity are evident among patients with SCD.

Competing interests
The authors declare no competing interests.

Authors' contributions
Gifty Gyamah Nyante and Emmanuel Bonney designed the study, coordinated the research, analyzed the data, interpreted the results and drafted the manuscript. Catherine Oppong supervised the data collection and helped to edit the manuscript. All authors read and approved the final manuscript.

Acknowledgments
We would like to thank patients and staff of the sickle cell clinic at the KBTH for making this study possible. We also express our gratitude to the students who participated in the data collection. Table 1: sociodemographic characteristics of participants