Vitamin D status of the elderly in the Vaal region, South Africa

Vitamin D status was determined in a sample of 79 elderly people and the results showed that 38% of the elderly had inadequate vitamin D status that was accompanied by various symptoms associated with vitamin D insufficiency/deficiency.


Introduction
Vitamin D insufficiency or deficiency has been recognised as a global public health problem. 1 Although the major source of vitamin D for most individuals is cutaneous photosynthesis from ultraviolet-B radiation through sunlight exposure (80%), many countries with adequate sun exposure have reported vitamin D insufficiencies/deficiencies. This is especially true for people with dark skin, whose increased melanin production may result in lower vitamin D synthesis. 2 The elderly are particularly at risk of developing vitamin D deficiency (VDD), 3 because of age-related declines in vitamin D production from sun exposure and limited dietary vitamin D sources. 2,3 Poor vitamin D intakes have been observed among the elderly in the Vaal region of Gauteng, South Africa. 4 Many VDD studies have focused on adults and the elderly during the last decade, but there is little information concerning the prevalence of VDD among the elderly in South Africa (SA). The aim of this study was to determine the prevalence of Vitamin D insufficiency and deficiency as well as identify symptoms associated with inadequate vitamin D status among black elderly individuals living in the Vaal region.

Methods
This study was carried out in July 2018 using a convenience sample of 79 of the surviving community-dwelling participants from a longitudinal study carried out since 2008. 4 All the respondents were homogeneous in age (≥ 60 years) and race (black). The study protocol was approved by the Vaal University of Technology Senate Research Innovation and Ethics Committee (20140827mns). All the participants completed and signed the informed consent forms for voluntary participation.
Trained fieldworkers assisted with data collection in one-on-one interviews with each of the participants. Measurements included age, gender and a questionnaire measuring various self-reported symptoms frequently associated with VDD.

Results
The mean ± SD age of the participants was 73 ± 30 years and 78.4% were women. The mean ± SD 25(OH)D 3 was 24.8 ± 10.5 ng/ml. The majority of the respondents (62.0%; n = 49) had adequate serum 25(OH)D 3 levels whereas 32.9% (n = 26) had insufficient and 5.1% (n = 4) deficient serum 25(OH)D 3 levels. Respondents with an adequate serum 25(OH)D 3 were significantly (p = 0.011) more likely to be men (81.8% versus 51.1% women). This was reflected in the higher mean ± SD serum 25(OH)D 3 levels of men (29.6 ± 9.5 ng/ml) compared with the women (23.3 ± 11.8 ng/ml) (p = 0.015). The ANOVA results in Table 1 showed that significantly higher prevalence of fatigue (p = 0.029) and low back/joint pain (p = 0.035) were experienced by the insufficient and VDD respondents compared with those who had adequate vitamin D status. In addition, the chi-square correlation analysis showed only one significant association (p = 0.036), namely between 25(OH)D 3 levels and low back/joint pain.

Discussion
A compromised vitamin D status was prevalent in a large percentage of the elderly. Many adverse associations have been reported between poor vitamin D status with chronic diseases and poor general health. 1,3 The elderly represent the fastest growing segment of the global population with a projected increase of 64% in Africa during the next two decades. Although this is a success story due to improvements in health care and hygiene, it also causes a burden for the healthcare and social security systems. Most of the symptoms associated with inadequate vitamin D status are also symptoms associated with old age, which makes it difficult to differentiate. In addition, although optimal levels of vitamin D result in less functional decline and fewer negative outcomes, 1,3,5 it is not clear from the body of evidence whether low levels of vitamin D are a cause or a consequence of poor health. 6

Conclusion and recommendations
Although this study had a small sample size, this is one of the first studies reporting on vitamin D status of communitydwelling elderly in SA and confirms poor vitamin D status as also observed among the elderly in other countries. A need thus exists for awareness and nutrition education programmes through which the elderly can be advised to increase their intake of vitamin-D-rich sources and motivated to spend more time outside in the sun.
Disclosure statement -No potential conflict of interest was reported by the author(s).