As low and middle-income countries work to compete in the global market, the health of their workforce is increasingly vital to enhance productivity. For many sub-Saharan African countries, infectious diseases like HIV/AIDS are still having a serious impact despite the large-scale campaigns for prevention, care and anti-retroviral therapy (ART) [1]. Non-communicable diseases (NCDs) are playing an important role, as changing diets and sedentary habits are adopted, particularly in urban settings [2]. Conditions like cardiovascular disease and diabetes are increasingly affecting countries in economic transition and are expected to increase dramatically over the next 20 years [3,4]. Despite these trends, funding to prevent and manage NCDs is significantly behind that of communicable disease [5]. This is remarkable in light of the fact that cost-effective and cost-saving interventions have been shown to prevent NCDs in developing countries [6] and are adaptable to the workplace.

For many sub-Saharan African countries, unlike high-income countries which have many more social support mechanisms in place, individuals pay out-of-pocket for their own care [7-9] which creates a significant barrier to access. As a result, individuals in the workforce faced with the high cost of managing disease have few options. There is some evidence of employers filling this gap by providing basic health care in the workplace [10]. Employers must balance the provision of health services and health insurance to their workers while maintaining profitability, taking into account the double burden of infectious and non-infectious chronic diseases. If the worker is not paid for some or all of the sick time, household income falls at the same time that medical care costs may increase. Furthermore, sickness related absenteeism is an indicator of the prevalence and severity of health conditions in the work force, an indicator that is not collected through the health system. Loss of productivity due to health-related absenteeism remains a barrier to productivity and thus to economic development. Gathering information regarding employee health can help employers make informed decisions to keep their workforce healthy and productive and reduce absenteeism as well as improving access to care for individuals.

Current research into absenteeism and its determinants, concentrated in high-income countries, has found that with regards to health, NCDs are contributing significantly to increased sick leave [11-14]. However, similar research among employees in sub-Saharan Africa has focused primarily on the contribution of infectious disease and in particular HIV/AIDS [15-17]. In addition, since HIV/AIDS has largely affected those of working age, it is important to understand the impact of being infected on employees and the workplace. In a previous study we reported on the HIV prevalence amongst the workforce in Namibia [18]. There is a gap in research looking more generally at the determinants of absenteeism among workers in sub-Saharan Africa. The findings from this paper will provide evidence that may help fill that gap and drive further research in this area.

Namibia represents a country in economic and epidemiologic transition in sub-Saharan Africa. It has one of the region's highest rates of gross-national income per capita at USD 4,210 in 2008, compared to an average of just USD 1,082 for all of sub-Saharan Africa [19]. However, the country is also characterized by one of the highest income disparities in the world [19]. While Namibia posts better than average performance on a number of economic measures when compared to the rest of sub-Saharan Africa [19], it has one of the highest national rates of HIV/AIDS at 13.3% [1]. The government has engaged in a substantial program to provide anti-retroviral therapy at a low cost and improve access to care [1]. This has resulted in almost universal coverage of anti-retroviral therapy. The majority of health services in Namibia are concentrated in a few cities in the north and center of the country [20]. This leaves a portion of the population without easy access to basic care. While the Ministry of Health and Social Services (MOHSS) has developed and implemented a program to improve access to care for more remote regions [20] it can still be a long distance to travel. As a consequence, large employers often provide basic healthcare services on site. In addition, some employers offer (co)payment of healthcare insurances for their employees (and dependents) through one of the existing Namibian medical aid schemes [10]. However, provision of these services is based on the perceived needs of the employee and employer rather than on actual evidence of disease risks and determinants.

This study is based on the results of wellness surveys that were performed at the request of employers from 7 different Namibian industry sectors. These wellness surveys are the most extensive yet in that country. The industry sectors assessed were retail, agriculture, fishing, services, wholesale, tourism and transport. In addition, the survey provides information on the prevalence of certain risk factors and conditions among different industries in the Namibian private sector. The primary goals of this paper are:

1. Describe the demographic and work profile of participants including industry, contract type, job type, age, gender, and the prevalence of risk factors and conditions such as hypertension, diabetes, HIV, hepatitis B, anemia and syphilis in the Namibia formal sector.

2. Describe the associations of the above determinants to self-reported sickness absence.

The survey was performed by two mobile clinics from the Bophelo! Project, a partnership between PharmAccess, the Namibian Business Coalition on AIDS and the Namibia Institute of Pathology. As part of the project, wellness surveys and health screening services are offered to companies based in Namibia along with sensitization and information sessions provided before employee screenings. The mobile clinic visits a company site for as long as required to see all participating employees (up to 32 people per van per day) and each screening visit takes an average of 30 min for pre- test counseling, testing, and post- test counseling sessions. All services are provided by MOHSS-trained testers and counselors, as part of a national task shifting effort. While screening results are being obtained, the participant receives health education and confidential counseling. Participants who tested positive for any condition or have screening results outside of a normal range are encouraged to seek follow-up consultation and are issued a referral letter to local medical services. Only de-identified information was collected from the screenings without any possibility of linking back to the participant. The study was approved by the Ministry of Health and Social Services of Namibia (MOHSS).

A total of 10,701 employees were offered the possibility to participate in the survey across all companies; 8,355 provided written informed consent, of which 100 were excluded from analysis because of pregnancy, as this was considered to be a risk for potential bias for absenteeism. 589 were excluded because of being younger than 20 years of age which could also bias findings on absenteeism. In summary, 7,666 participants were included in this analysis. Participants were asked to recall how many days they had missed work due to sickness in the 90 days prior to administration of the survey. To preserve confidentiality, this measure was based entirely on participant recall and not compared to employer records.

Participants who provided informed consent were asked to complete a questionnaire with demographic (age, sex, marital status, smoking), job status information (contract type, type of position), and self-reported presence of the following conditions: HIV/AIDS, diabetes, and hypertension. In addition, participants who agreed received a medical screening including risk factors (haemoglobin, systolic and diastolic blood pressure and anthropometric markers: height, weight and waist circumference) and prevalence of diseases (HIV status, hepatitis B antigens, syphilis, random blood glucose for diabetes). A finger prick was conducted on all participants to collect a blood sample for the following rapid tests: HIV, syphilis antigen, hepatitis B antigen, haemoglobin and blood glucose. Participants were allowed to refuse any or all of these screenings.

The following assays and methods were used for collecting medical screening information according to manufacturer instructions. Any test with an inconclusive or discordant result was repeated. For HIV testing, the Determine HIV 1/2 Assay by Inverness rapid test strip and Trinity Biotech Uni -Gold HIV 1/2 test kit were used in conjunction for HIV testing, according to Namibian VCT regulations. If the result was discordant between the two tests, a third (tie-breaker) test was performed using the Inverness Clearview Complete HIV 1/2 test kit. Hepatitis B testing was done using the Determine HBsAg Whole Blood Assay rapid test strip (Inverness Medical, USA) was used. The Determine Syphilis TP Whole Blood Assay (Inverness Medical, USA) was used for presence of syphilis antibodies. The Accutrend Plus GCT meters were used to test blood glucose (Roche Molecular Diagnostics, USA). HemoCue Hb 201+ Analyser and HemoCue Hb 201+ microcuvettes (HemoCue, USA) were used to conduct haemoglobin tests. Systolic and diastolic blood pressure was measured in millimetres of mercury (mmHg) by using the MG150f Digital Blood Pressure monitor (Rossmax International Ltd, Taiwan). The measurement was taken three times on each participant and the average of the three readings was used. A blood pressure reading above 140/90 mmHg was considered elevated; above 153/103 mmHg was considered high and referral was made to a medical facility.

Bodyweight was measured with light clothes on, without shoes on an analogue scale and the recorded value was rounded to the nearest 0.5 kg. Height was measured in centimeters using a non-stretch retractable measurement tape to the nearest 0.5 cm. These were used to calculate body mass index according to the formula below.

A BMI of 25-30 was considered overweight; above 30: obese. Waist circumference was measured at the level of the umbilicus in standing position with the hands by the side and the feet together at the end of a normal expiration. A no-stretch retractable tape was used. Measurements were rounded to the nearest 0.1 cm. A waist circumference above 102 cm in men and 88 cm in women was considered above normal and indicative of central obesity.

Only aggregate results were reported back to the employer. Individual screening results were given directly to the participant. Based on individual participant results, the person was advised to make an appointment with a clinician for confirmation and further medical follow-up. In addition, participants with screening results outside the above indicated normal values or who tested positive for any condition were given a letter of referral for a follow-up visit with a clinician including a description of the findings of the screening.

Two variables were created based on a combination of findings from clinical screening and participant responses. Diabetes was classified as known diabetes or those whose random blood glucose was 11.1 mmol/L or higher. Similarly, hypertension was classified as known hypertension, as well as those who were found at screening to have systolic blood pressure above 154 mmHg or diastolic blood pressure above 104 mmHg.

Data were collected and stored using SPSS. All participants received counseling and information on their results and were invited to speak with a trained health professional or to schedule a follow-up with a physician.

Namibia enacted the Labour Act in 1992, which was revised in 2007 (Act 11, 2007). Both the old and new Labour Act gives all employees (permanent and short-term contracts) a right to sick leave. The Labour Act states that during the first 12 months of employment, employees who work 5 days per week accrue 1 day of sick leave for every 5 weeks of employment. Employees that work 5 days per week are entitled to 30 working days of sick leave and those working 6 days per week can take up to 36 working days of sick leave, in a 3 year cycle. While the law may not be applied consistently everywhere, the majority of companies comply in providing paid sick leave [24]. A medical certificate is also required for sick leave, which may act as a barrier to some seeking care given that they may have to pay out-of-pocket. In addition, employers are required to pay employees full salary benefits for the allowed sick leave. However, there are no studies published looking at employer compliance with the law and the effect on employee absenteeism in Namibia. It is possible that employees may not use sick leave if they know they will not be compensated or that there may be some threat to their position from several absences.

There are a number of reports examining absenteeism rates in Europe and the United States. These reports show average sick leave rates ranging from 5.1 days per year for employees in Europe to just over 8 days per year for employees in the United States and up to 12 days per year for public sector employees in those countries [25,26]. Assuming the same rates of absenteeism in this study hold for the full year, we could expect there to be an average rate of sick leaves taken by the study participants close to 4 days per year. This calculation would put Namibian absenteeism rates in the formal sector somewhat below the estimates from the United States and Europe. Similar statistics for neighboring sub-Saharan African countries were not readily accessible. Despite much progress toward strengthening the health system, access to care for Namibians remains an area of concern. Public health facilities, which are the most accessible, are understaffed and patients may have to pay out-of-pocket [27]. These barriers to access may also be reducing absenteeism as employees decide to continue working rather than trying to seek care.

Compared with current research on absenteeism in the workplace, this study looks at a variety of health-related determinants without focusing on any one condition. It provides some insight into the prevalence of different risk factors and conditions among workers in various industries as well as the relative impact of those factors on absenteeism. The majority of absenteeism research is focused on high-income countries [11-14], and highlights the effect of particular chronic conditions on absenteeism. The findings of these studies consistently find a strong association between NCDs, their risk factors, and increased absenteeism. For most absenteeism-related studies in high-income countries, the recall period is longer and can be validated against employee records which help minimize recall bias. This level of information is not available for the current study as with many studies looking at sickness work absence in a sub-Saharan context [9,15-17]. As a result, the true level of absenteeism in this population may be underestimated as a result of recall bias or may be subject to whether employees have access to basic care services provided by some of the employers, as with the agriculture sector [10].

It is apparent from findings in Table ​Table33 that NCDs and their associated risk factors are affecting the working population in Namibia. This is consistent with findings from studies in high-income countries [11,12]. This survey found a relatively high proportion of central obesity (18.7%) and elevated or high blood pressure (27.0%). In addition, diabetes had a significant impact on the rate of sick days although affecting a relatively low proportion of the population (1.7%). Moreover, anaemia which may be caused by a large number of conditions, including HIV, was also found to affect absenteeism. The mix of NCD and communicable disease is in line with the epidemiological transition that many low- and middle-income countries face today [28].

The most significant finding of this study is the association of diabetes with absenteeism. Random blood glucose is not a rigorous test for conditions like impaired glucose tolerance or diabetes and is sensitive to whether a person has eaten recently. However, the American Diabetes Association has established that a random blood glucose measurement above 11.1 mmol/L is very likely a sign of diabetes [22]. Therefore, although the actual diagnosis of diabetes could not be made, the current glucose results suggest that diabetes has an important impact on absenteeism and employee health.

Almost half of those who were overweight or obese also had high blood pressure readings and elevated blood glucose. This finding is compatible with other studies that have shown that the majority of people diagnosed with one non-communicable disease have co-morbidity with another [28,29]. NCDs share many common risk factors and several of those are modifiable, especially through lifestyle changes. These shared factors provide an opportunity for prevention strategies centered on improving diet, physical activity, and smoking reduction. Education strategies to reduce these risks could be included in workplace wellness programs and could have an effect on both the health of employees and reducing absenteeism.

Despite showing a less significant impact on absenteeism in this study, HIV is still a significant determinant of increased sick days. In the current study it is not possible to determine reasons for sick leave or to directly relate absenteeism to HIV. It is possible that some employees missed work in order to access ART care in a location away from their workplace. Conversely, it is possible that a number of the HIV positive workers are still in the early phase of infection and therefore are not yet on ART. These people could have more frequent (short) episodes of sickness, as compared to HIV negative people or HIV positive people on ART. HIV positive workers could also have other HIV positive family members and take more frequent sick leave days to care for them.

Discovering the reasons behind diabetes- and HIV-related absenteeism may help the private sector provide services that minimize costs lost to employee sickness. For the fishing sector, prevalence of HIV appeared much higher than the average for the whole population (14.3% compared to 9.0%, respectively). Where HIV/AIDS is more prevalent in certain sectors, special attention should be given to providing adequate services such as prevention education and ART. The lower relative impact of HIV/AIDS compared to diabetes may be a result of successful intervention programs already in place among employers, including the exemplary high ART coverage achieved in Namibia [30].

The impact of conditions like hepatitis B and syphilis were negligible and did not contribute to increased rates of sick days in the short-term. Prevalence estimates for hepatitis B surface antigen were below those reported for sub-Saharan Africa (> 8%) [3]. The same was true for syphilis, which is well below average rates reported in general population surveys in Africa [3]. Given the natural progression of these diseases in the absence of treatment, it is possible that infection could lead to long-term disability and contribute to future loss in overall productivity for companies with a large proportion of affected employees [24].

The fishing, services, and wholesale sectors had significantly higher rates of sick days when compared to the largest sector in this study, retail, even after controlling for other factors. The prevalence of HIV and diabetes were some of the highest in these sectors as well, which may indicate causal relationships. Conversely, the agricultural sector had significantly less absenteeism, perhaps because a number of farms in Namibia provide health-related services on site to their employees [20].

All of the above results are possibly subject to a bias toward workers who are fit enough to attend work on the day of the screening. If this is the case, the effects reported here are an underestimate of the true impact of these and other health factors on sick days for workers in Namibia.

Ingrid de Beer is a full time employee of the PharmAccess Foundation in Namibia.

Rina Hough is a full time employee of the PharmAccess Foundation in Namibia.

Els Bindels is a full time employee of the PharmAccess Foundation in Namibia.

Delia Weimers-Maasdorp is a full time employee of the PharmAccess Foundation.

Frank Feeley is professor of international health at the Boston University School of Public Health.

IDB - contributed to the design and conduct of the study as well as providing information on the Namibian formal sector.

RH - conducted the data collection, cleaning, and primary descriptive analyses. DWM - designed the survey instrument and conducted the survey.

FF - contributed to the analysis with methods on occupational health research and revised the manuscript.