Academic Research Study Conventions: Much like an academic article, an academic research study also seeks to produce unique, original findings, but typically involves running a research experiment that produces primary data that is unique to that research study.  Writing in this model uses a more scientific approach and includes fairly standard sections (methodology, results, discussion, conclusions, etc).  Proper citation and referencing is expected as well. 

Ginter, J. K., Krithika, S., Gozdzik, A., Hanwell, H., Whiting, S., & Parra, E. J. (2013). Vitamin D Status of Older Adults of Diverse Ancestry Living in the Greater Toronto Area. Faculty Publications and Scholarship 1. Licensed under CC BY-NC-ND 4.0. Retrieved from https://source.sheridancollege.ca/fhass_soci_publ/1

Research STudy: Vitamin D Status of Older Adults of Diverse Ancestry Living in the Greater Toronto Area

By Jaime K. Ginter, S Krithika, Agnes Gozdzik, Heather Hanwell, Susan Whiting, and Esteban J. Parra

Vitamin D plays a key role in bone development and mineralization, and it is also involved in the regulation of cell growth and immune function [^{[1] [2] [3] [4]}]. Physiological and lifestyle factors put older adults at an increased risk of vitamin D insufficiency and the resulting negative health outcomes. Cutaneous vitamin D synthesis is less efficient in older individuals due to the age-associated decline of concentrations of 7-dehydrocholesterol, which is the key precursor for the synthesis of vitamin D through the action of ultraviolet B (UVB) light in the skin [^[5][6][7]]. Additionally, factors such as reduced mobility, and limited outdoor exposure, may also negatively influence vitamin D status – as measured by 25-hydroxyvitamin D (25(OH)D) levels – in some older individuals [^{[8][9][10][11][12][13]}].

Numerous studies have reported that low 25(OH)D levels are associated with osteoporosis and fractures in the elderly [14,15], and these are some of the most important health concerns for this age group: osteoporosis is the suspected cause of over 300,000 hip fractures in the United States, and 24,000 hip fractures in Canada every year [16]. Long term care and health costs associated with osteoporosis-related fractures have been estimated at $13.8 billion in the United States in 1994 and $1.3 billion in Canada in 1993 [16]. Additionally, there is evidence that vitamin D supplementation may provide some benefit for physical performance in older persons [15].

Information about the vitamin D status of older adult Canadians of diverse ancestry is limited. Available studies have focused on European populations [13,17,18] or older adults of European ancestry [19,20], and to lesser extent African ancestry [21] residing in North America. Detailed descriptions of ancestry are often not reported in vitamin D studies, including national surveys in Canada [22] and older persons of diverse ethnicities have been found not to be included in meaningful numbers in studies exploring vitamin D status [15]. In particular, it is critical to obtain reliable information for darkerskinned individuals, who are at higher risk of vitamin D insufficiency because melanin (the main skin pigment) interferes with cutaneous production of vitamin D [22,23]. The aim of this study was to explore the wintertime vitamin D status of an understudied segment of the Canadian population: older adults of diverse ancestry. Secondly, we wanted to contrast our findings with previous studies of 25(OH)D levels in older adults [22,24-26], and a previous study of young adults of diverse ancestry living in the Greater Toronto Area (GTA) [23].

* Data from Gozdzik et al. [23].

^ Absolute numbers and proportions (in parentheses) are reported.

smaller than the mean differences observed in the older adult and young adult samples. Another caveat to interstudy comparisons is that the data collection in the older adult study took place in April/May, a period in which endogenous vitamin D synthesis is possible in Southern Ontario. The data collection in the young adult study took place in January/February when no synthesis was possible; these seasonal disparities between studies may also contribute to the higher 25(OH)D levels observed in the present study of older adults. Another difference between the two studies was that in the young adult study we excluded individuals who travelled to sunny locations prior to participating in the study, and this was not a criterion of exclusion in the older adult study. Mitigating concerns about this difference is the observation that, in the present older adult study, 25(OH)D concentrations did not significantly differ between participants who travelled to sunny destination during the three months prior to their involvement in the study and those who did not travel. In fact, individuals who did not travel (n = 156) reported slightly higher mean 25(OH)D levels (mean = 83.6 nmol/L) than those who did travel (n = 68, mean = 79.6 nmol/L). In summary, we conclude that the observed differences in vitamin D status between the older and young adults are largely driven by the substantially higher daily supplementary vitamin D intakes in the older adults – 917 IU/day on average, compared to only 114 IU/day in young adults.

Older adults
We also compared our findings with those of three Canadian studies that surveyed older adults, the Canadian Health Measures Survey (CHMS) [22,24], the Canadian Community Health Survey (CCHS) [25], and a recent report focusing on 25(OH)D levels in older individuals residing in long term care in the same geographic area where our study was conducted, Mississauga, Ontario [26].

The CHMS reported the vitamin D status in a sample of older Canadians aged 60–79 years (in addition to other age groups). This survey reflected the Canadian population having > 80% of European ancestry, but the number of participants of other ancestry groups was too low to carry out meaningful comparisons. The proportion of older adults in the CHMS study with 25(OH)D serum concentrations < 50 nmol/L (measured with the LIASON 25-Hydroxyvitamin D Total assay) was similar to the proportion observed in our study (14.4% vs. 12.1%, respectively). The mean 25(OH)D concentrations in older adults (males and females) taking supplements vs. those not taking supplements were similar in both studies: Females taking supplements had mean 25(OH)D concentrations of 89.2 nmol/L and 84.4 nmol/L in our study and the CHMS study, whereas the concentrations for females not taking supplements were 66.2 nmol/L and 61.9 nmol/L, respectively. For males taking supplements, 25(OH)D concentrations were 78.9 nmol in our study vs. 83.1 in the CHMS study, whereas males not taking supplements had lower mean concentrations of 61.5 nmol/L and 63.1 nmol/L, respectively.

The Canadian Community Health Survey [25] collected information on dietary vitamin D intake across the country. This survey did not explore specific ancestral differences in vitamin D intakes, so the mean dietary intake for our total older adult sample was used in the comparative analysis. We restricted our comparisons to the information available for two groups of older adult Ontarians (51–70 yrs, and >70 yrs). The dietary intakes ranged between 6.5 ug/day (260 IU/day) in the CCHS sample of male adults aged 51–70 yrs and 4.7 ug/day (188 IU/day) in our sample of older adult males aged 60–70 yrs. There were no significant differences in vitamin D dietary intakes estimated in our sample and the CCHS.

Finally, a recent paper by Ioannidis et al. [26] described 25(OH)D concentrations and vitamin D supplement use in approximately 100 older residents living in four long term care facilities in Mississauga. Only 49.0% (48/98) of the residents were taking vitamin D supplements. This contrasts with the proportion of older adults in our study taking vitamin D supplements, 76.8% (172/224) (p < 0.001). Ioannidis also reported that mean serum 25 (OH)D concentrations in individuals not taking supplementation was 62.6 nmol/L, and the mean levels were 72.9 nmol/L, 98.9 nmol/L and 96.0 nmol/L for individuals taking vitamin D supplementation of 0–400 IU/ day, 401–800 IU/day, and > 800 IU/day, respectively. Using the same cutoffs as Ioannidis, we found very similar concentrations in our sample. Participants taking no supplementation, 0–400 IU/day, 401–800 IU/ day and > 800 IU/day had mean 25(OH)D concentrations of 65.0 nmol/L, 72.7 nmol/L, 83.6 nmol/L and 90.9 nmol/L, respectively. Therefore, we observe that in both studies the mean 25(OH)D concentrations increase with the amount of vitamin D supplementation, and the mean concentrations in each supplementation group are quite similar. However, the proportion of older adults in our community dwelling sample taking vitamin D supplements was substantially higher than in the older residents living in long term care facilities (76.8% vs. 49.0%, respectively). Another recent Canadian study that analyzed vitamin and mineral supplements in a long-term care residence has indicated that only 35.4% of all the residents in the facility took vitamin D supplements [33].

In general, our results show good agreement with the results of other Canadian older adult studies in terms of (i) the proportion of individuals with 25(OH)D concentrations < 50 nmol/L (our study vs. CHMS study), (ii) the 25(OH)D concentrations amongst individuals taking vitamin D supplements and those not taking supplements (our study vs. CHMS study vs. Ioannidis study), and (iii) the mean daily vitamin D dietary intakes (our study vs. CCHS study). However, the comparison of our study, in which we sampled community dwelling older adults, and two studies which sampled older adults in long term care residences [26,33], seems to indicate that the percentage of older adults living in long term care residences taking vitamin D supplements is considerably lower. This emphasizes the need to carry out studies that are more representative of the broader Canadian older adult population to explore in more detail to which extent there are differences in vitamin D supplementation between community dwelling older adults and long term care residents, and how this potential difference influence vitamin D status.

This study is not without limitations. The study participants were community dwelling, active older adults, and thus are not representative of the entire older adult population living in the GTA. Members of the SOOAC are probably more mobile and healthier than the general older adult population in this region, on account of their membership in a community organization that promotes active, healthy aging. Furthermore, it is possible that the members of the SOOAC who volunteered to participate in our study may represent those members that are interested in healthy ageing, aware of the benefits of vitamin D and actively supplementing with vitamin D.

Previous studies have reported that institutionalized and home bound [8,9,12,13] older adults are at a higher risk of vitamin D deficiency than community dwelling older adults. Indeed, as described above, the comparison of our results with those of two studies focusing on older adults living in long term care residences supports this concept in that the proportion of individuals taking vitamin D supplements is much lower amongst those in long-term care vs. those in the community. We also encountered some challenges in the application of the food frequency questionnaire, some of which are common to studies using this tool to estimate dietary intakes. Some participants experienced difficulty providing accurate estimates of their average weekly diet and some individuals did not complete serving sizes for all dietary questions. Language limitations were another issue for some of the participants. Despite the SOOAC being a highly integrated, diverse centre, there were some individuals for whom English proficiency was an issue. This was especially true for one of the cultural groups, for which many members did not speak or read English to the level required for this study. This issue was resolved by translating the questionnaires into the native language and having one of the coordinators of this group translate and assist those participants who were not proficient in English with the completion of the questionnaires. Given that the vitamin D dietary intakes estimated in this study were not significantly different to those reported in other studies [22,23], it is unlikely that the aforementioned issues had a major impact on our estimates of vitamin D intake. Finally, the only criterion for exclusion in this study was age. We did not exclude participants based on other criteria, such as recent trips to sunny destinations, use of certain medications, or medical conditions, all of which may have an effect on vitamin D metabolism. As such, we feel that we were best able to obtain a broad representation of community dwelling older adults of diverse ancestry.

Conclusions

In conclusion, in this study we observed that the mean circulating 25(OH)D concentrations in a group of community dwelling older adults of diverse ancestry living in the GTA slightly exceeded 80 nmol/L and did not significantly between the three ancestral groups (East Asians, Europeans and South Asians). In terms of the health implications of our study, the most relevant figure is the proportion of participants with suboptimal vitamin D levels. Using the IOM cutoff of 50 nmol/L, approximately 12% of the participants would have been classified as insufficient. However, using the higher cutoff of 75 nmol/L, the proportion of participants with vitamin D insufficiency would be nearly 40%. Dietary vitamin D intakes were relatively low (<200 IU/day), and, thus, insufficient to cover the daily requirements established by the IOM (600–800 IU/day) and many other health agencies. In contrast, intake of vitamin D supplements exceeded IOM recommendations and was the main determinant of 25(OH)D levels. Moreover, the prevalence of insufficiency was substantially higher amongst individuals not taking supplements, irrespective of the cutoff used. Our results indicate that taking vitamin D supplements is important to ensure optimal vitamin D levels, particularly in the Canadian winter when there is insufficient ultraviolet B radiation to cutaneously synthesize vitamin D. This is of particular relevance for older adults, who are more vulnerable to vitamin D insufficiency and deficiency than other age groups, due to a number of physiological and lifestyle factors.

Abbreviations
SOOAC: Square One Older Adult Centre; CHMS: Canadian Health Measures Survey; CCHS: Canadian Community Health Survey.

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*This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License