Results from this study highlight that a large portion of educated young adults views sunlight exposure negatively. A similar negative attitude was reported in a study from India, albeit conducted on limited number of biotechnology students only [16]. Regarding the potential influencing factors behind such a negative attitude, fear of the health risk due to exposure to UV radiation in the sunlight of Bangladesh was predominant (Figure 1). However, according to the World Health Organization (WHO), the UV intensity can be classified as 'very high' when the UV index ranges between 8-10 [23]. But the monthly average of the highest daily UV index in Bangladesh ranges from 6 to 7 due to Bangladesh being located in a subtropical region, sunlight intensity remains moderate throughout the year [19]. It should be noted that this range represents only the peak during mid-day for a short duration, implying the UV index remains below 6 for most of the day. Furthermore, WHO’s classification of health risk from UV-exposure did not take into account the other confounding variables like skin complexion. According to the Fitzpatrick scale, unlike the European population (who have skin type of I or II), people from the Indian subcontinent (India, Bangladesh, and Pakistan) have skin type IV and V which is naturally much more protected from harmful solar radiation due to high melanin concentration [24, 25]. Indeed, Bangladesh ranks 183 (and India ranks 173) among the list countries for skin cancer-rates refutes the hypothesis that UV radiation in the sunlight in Bangladesh is indeed a big health concern [26]. Therefore, the fear of 'very high' UV is an overestimation which might have led to a belief that sunlight exposure would be 'unsafe' for health, which is perhaps influencing sun-exposure practices in the wider community. Indeed, this has been reflected in the fact that 72% of the respondents reported they used some sort of sun-protection items to be protected from the adverse effects of sun exposure.
In addition to the exaggerated fear of adverse health effects, high admiration for fair skin complexion especially in the case of females is a deeply ingrained cultural aspect in South Asia [10, 11]. Accordingly, 51% of the respondents of this study identified that getting darker skin due to sunlight exposure was a 'problem' (Figure 1). This concern about skin complexion was found significantly higher among the female participants of this study; p < 0.01; supplementary Table S1). This is found in line with the overall negative attitude to sun exposure (e.g., fear of very high UV radiation and belief that sunscreen should be used regularly) also being significantly higher among the young female participants of this study (p < 0.01). In this regard, the commercial advertisements promoting fair skin and the portrayal of sun exposure as a problem (also identified in this study as the second most important source of negative perception about sunlight) could be making young females more vulnerable. Such aggressive advertisements have been reported in the past as a stimulator for perpetuating the negative attitude towards sunlight [27]. Therefore, we argue that continuous review and regulation of the aggressive (misleading or even false) commercial narratives targeting the young population promoted by companies that benefit from the fairness products is strongly recommended as this might be contributing to the high prevalence of vitamin D among the young adults. This can be a really important step to protect a vulnerable community (due to young age) that is mostly unaware of the importance of vitamin D and the prevalence of its deficiency in the community.
Regarding the sources of knowledge and attitude regarding the effects of sunlight exposure, 'doctors’ advice' was identified as the most important. However, albeit unexpected, another recent study conducted by our group has identified that the majority of the healthcare providers in Bangladesh were overly concerned about the level of harmful UV radiation in the sunlight in Bangladesh [28]. Indeed, a high majority of the medical practitioners could not identify the time from 10 am to 3 pm as the best time to get vitamin D from sunlight in Bangladesh. Therefore, it is highly plausible that the attitude of the educated young adults in this study was perhaps negatively influenced by that of the medical practitioners.
While it was beyond the scope of this project to test serum vitamin D for the participants, response to one particular question could be revealing. Based on the potential symptoms commonly associated with vitamin D deficiency, 47% identified themselves as potentially deficient, while 28% were unsure. Albeit arbitrary, the self-identified deficiency was higher among the females; 52% of the females compared to 40% of the males; p < 0.01 (Figure 2). Indeed, a similar trend has been reported in a systematic review from South Asia (76% of females and 51% of males are affected by vitamin D deficiency) [7]. Despite some recent literature showing the overall prevalence of vitamin D deficiency is very high in Bangladesh [7-9], 85% of the participants said they never checked their serum vitamin D level. This is perhaps a reflection of widespread vitamin D deficiency in South Asia being a seriously overlooked public health concern. While the high expense associated with testing serum vitamin D might be a contributing factor, lack of knowledge and awareness could also be crucial determinants in this case.
In line with negative attitude, knowledge about the most crucial vitamin D-related aspects was indeed suboptimal. This applies to the best time in the day for the production of vitamin D from sunlight, the symptoms associated with the deficiency of this vitamin, as well as its potential long-term consequences (Figure 2). The highest number of participants believed only 15-30 minutes of weekly sunlight exposure would be sufficient for the production of adequate vitamin D. In this regard, based on data from multiple studies, Holick et al. (2007) suggested that 5 to 30 min of sunlight exposure twice a week could often be sufficient [2]. However, this recommendation was made mostly based on studies not conducted on the South Asian population. Considering the darker skin complexion and heavier clothing practices in this region, high caution should be practiced before generalizing this recommendation for South Asia. Indeed, this was later highlighted in other literature [29, 30]. As such, while further research is needed in this regard, it is perhaps safe to assume that the required weekly sun exposure for the South Asian population, and for Bangladeshis as such, would be >30 minutes per week, which was identified by only 14% respondents of this study. As such, finding the right ways to disseminate correct knowledge among young adults could be crucial. But how?
While increasing the number of diagnostic centers for detecting serum levels of vitamin D, encouraging people to take foods rich in vitamin D, and considering food fortification programs are important steps, it is also necessary to consider the socioeconomic context for any policy to be effective. Therefore, a parallel policy towards encouraging people to get sun exposure can be an easy and low-cost option for Bangladesh (and other regions with similar context), since sunlight is abundant throughout the year. However, further research is warranted before making such recommendations to determine the actual levels of ultraviolet radiation throughout any country, and its direct and indirect effects on human health, especially during high UV intensity periods. Large-scale prospective/experimental studies to determine the minimum duration required for the production of vitamin D for different skin complexions should be considered a high priority. Also, attention should be given to finding/establishing effective mass communication strategies (e.g., including relate information in the textbooks, and engaging the medical community) can be considered to disseminate correct knowledge and awareness among the wider community about the critical role of sun exposure for the human body as well as the relevant safety aspects.
To the best of our knowledge, the sample size of 3,673 is the highest among all the studies related to knowledge, attitude, and practices conducted in South Asia and possibly beyond. Furthermore, instead of focusing on a specific demographic group (e.g., medical students, pharmacy students, etc.), the demographic diversity of this study is perhaps more representative than any other similar study. Hence, the insights gained from this study would be really helpful to get a holistic view of the mindset of young adults.