Abstract

This article aims to analyze vitamin D insufficiency and factors associated among older adults using primary health care services. This is a cross-sectional study that evaluated 533 older adults individuals (≥ 60 years old) in three cities in the state of São Paulo, Brazil. Serum level of 25-hydroxyvitamin D (25-OHD) was evaluated by chemiluminescence. The factors evaluated were sociodemographic information (sex, age group, ethnicity, education, income, marital status), health conditions (reported diseases), body composition (BMI, waist circumference), lifestyle (physical activity and smoking), and sun exposure (purpose, duration, frequency, time of exposure, exposed body parts, use of sunscreen, skin type). The prevalence of vitamin D insufficiency was 64.5%, presenting association with female participants, non-white/unreported ethnicity, low weight, high waist circumference (risk for CVD - cardiovascular disease), and physical inactivity. Negative association was observed with habitual sun exposure of hands, arms and legs, during leisure activities, daily commuting and physical activity, and between 9 am and 3 pm. The findings show the relevance of factors such as sex, ethnicity, body composition, physical activity, and sun exposure habits in the high prevalence of inadequate levels of vitamin D among older adults.

Key words:
Elder people; Vitamin D; Sun exposure; Public health

Introduction

Vitamin D has a very clear role in bone mineralization; it has been highlighted for its complex activity in the body, including control of metabolic processes. Proper levels of vitamin D are suggested to help protect the body against musculoskeletal disorders, infectious diseases, cancers, autoimmune and cardiovascular diseases, diabetes mellitus, and neurocognitive dysfunctions, with low serum concentrations of vitamin D related to increased risk for development and progression of these diseases¹1 Wimalawansa SJ. Non-musculoskeletal benefits of vitamin D. J Steroid Biochem Mol Biol 2018; 175:60-81..

Cutaneous synthesis regulated by sunlight is the main source of vitamin D in humans, so there is a false impression that vitamin D deficiency is not a problem in sunny countries, and for this reason, serum concentrations of vitamin D in the population are not often measured. However, according to studies conducted in Brazil and other countries, hypovitaminosis D is highly prevalent, regardless of the region evaluated, with Brazilian studies showing prevalence ranging from 28.5% according to a study conducted with hypertensive older adults in João Pessoa, Paraíba, in spring and summer, to almost 96%, as reported in another study that evaluated older adults in São Paulo, SP, in winter²2 Mendes MM, Hart KH, Botelho PB, Lanham-New SA. Vitamin D status in the tropics: Is sunlight exposure the main determinant? Nutr Bull 2018; 43(4):428-434..

A study by Cabral et al.³3 Cabral MA, Borges CN, Maia JMC, Aires CAM, Bandeira F. Prevalence of vitamin D deficiency during the summer and its relationship with sun exposure and skin phototype in elderly men living in the tropics. Clin Interv Aging 2013; 8:1347-1351., which evaluated 234 older adults male individuals in Recife, Pernambuco, in summer, found 66.7% prevalence of vitamin D insufficiency, with mean serum concentrations of 25-hydroxyvitamin D below the recommended level (27.86 ± 13.52ng/mL). These mean values are similar to those found in another recent study⁴4 Santos CS, Bessa TA, Xavier AJ. Fatores associados à demência em idosos. Cien Saude Colet 2020; 25(2):603-611. conducted with 287 older adults from a community in Palhoça, Santa Catarina (26.09 ± 9.20ng/mL).

In addition to sun exposure, many other factors may be involved in vitamin D deficiency, such as age, skin pigmentation, obesity, multimorbidity, and use of certain medications like antihypertensive, anticonvulsant, anti-inflammatory, and sedative medications. Due to lifestyle habits, polypharmacy, multimorbidity, and reduced effectiveness of vitamin D production in the skin, the older adults are one of the most important groups at risk for vitamin D deficiency⁵5 Moreira CA, Ferreira CEDS, Madeira M, Silva BCC, Maeda SS, Batista MC, Bandeira F, Borba VZC, Lazaretti-Castro M. Reference values of 25-hydroxyvitamin D revisited: a position statement from the Brazilian Society of Endocrinology and Metabolism (SBEM) and the Brazilian Society of Clinical Pathology/Laboratory Medicine (SBPC). Arch Endocrinol Metab 2020; 64(4):462-478..

In this context, considering that few studies have assessed representative samples of older adults in primary health care in Brazil⁶6 Oliveira GBVP, Nunes IFOC, Carvalho LR, Figueirêdo RG, Oliveira MCB, Carvalho CMRG. Perfil antropométrico e níveis séricos de vitamina D de idosos participantes do programa saúde da família de Teresina. Rev Interd Cien Saude 2014; 1(1):48-55.^,77 Oliveira GBVP, Silva Júnior FL, Oliveira MCB, Carvalho CMRG. Relação dos índices antropométricos e vitamina D com o desempenho funcional em idosos TT - Relationship of anthropometric indices and vitamin D with functional performance in elderly. Estud interdiscip Envelhec 2018; 23(1):43-59., and knowing that serum vitamin D is not widely tested in the older adults population using primary health care services, factors must be identified for an early identification of vitamin D insufficiency, enabling actions and strategies to prevent and control this condition, which has become more prevalent in Brazil and worldwide. This study aims to analyze the prevalence of vitamin D insufficiency and its association with sociodemographic variables, sun exposure habits, physical and health conditions in older adults using primary health care services.

Methods

Participants

This is a cross-sectional study, which is part of a larger study titled “Evaluation on the prevalence of micronutrient deficiency in older adults living in cities in the region of Campinas - SP,” conducted in the municipalities of Limeira, Piracicaba, and Campinas, in the state of São Paulo, Brazil.

The inclusion criteria for study participation were: aged 60 years and older, living in one of the study municipalities, and presenting proper neurological and cognitive conditions to answer the questionnaires (as assessed by the interviewer during the study presentation and invitation to participate). Exclusion criteria were: use of food supplements based on vitamins and/or minerals, participation in a home care program, and receiving chemotherapy treatment.

The study sample was estimated considering the total number of inhabitants aged 60 years and older in the municipalities of Campinas, Limeira, and Piracicaba using official data of population estimates for 2018 and considering a prevalence of 60% of older adults with deficiency of at least one of the evaluated nutrients, considering a sampling error of 10% and 95% confidence level. Then, the total sample was 600 older adults, with 250 participants from the city of Campinas, 170 from Limeira, and 180 from Piracicaba.

Data were collected from 612 participants from October 2018 to December 2019 (no data collection was performed during the winter); 17 individuals had incomplete data and 62 who reported using supplements containing vitamin D were excluded, so the final sample had 533 individuals.

The older adults volunteers were recruited through an invitation made at the basic health units (UBS) recommended by the respective Health Departments of each municipality.

This study was approved by the Ethics Committee for Research with Human Beings from Universidade Estadual de Campinas, study approval No. 2.878.652 and CAAE 95607018.8.0000.5404. All participants signed an informed consent form.

Data collection

In each selected health unit, the older adults patients were invited by the research team to participate in the study and instructed to come back on the scheduled date with at least 8-hour fasting. On the scheduled day, a blood sample was collected, anthropometric data were measured, and then an interview was conducted to answer the questionnaire. These procedures were performed by a team of undergraduate and graduate health students, previously trained by the research coordinators.

Study variables

The dependent variable of the study was vitamin D insufficiency. Serum vitamin D levels were analyzed by measuring 25-hydroxyvitamin D (25-OHD) using the chemiluminescence immunoassay technique, with the Alinity 25-OH Vitamin D reagent kit (Abbott). The tubes containing collected blood were stored in a cooler with ice, and immediately at the end of collection, they were sent to the same private laboratory hired for this study (Pasteur^®), where the samples were processed and then analyzed (no freezing). For serum 25-hydroxyvitamin D levels, the reference values recommended by Brazilian Society of Endocrinoloy and Metabology (SBEM) and Brazilian Society of Clinical Pathology/Laboratory Medicine (SBPC)⁸8 Ferreira CES, Maeda SS, Batista MC, Lazaretti-Castro M, Vasconcellos LS, Madeira M, et al. Consensus - reference ranges of vitamin D [25(OH)D] from the Brazilian medical societies. Brazilian Society of Clinical Pathology/Laboratory Medicine (SBPC/ML) and Brazilian Society of Endocrinology and Metabolism (SBEM). J Bras Patol Med Lab 2017; 56(6):377-381. were used, so values below 30 ng/ml were considered vitamin D insufficiency.

The study covariates were: sex, age group, ethnicity, monthly income, physical activity, smoking, self-reported diseases, body mass index (BMI), waist circumference, sun exposure, use of sunscreen, sun exposure time, part of the body exposed to the sun, duration of sun exposure, frequency of sun exposure, and skin types.

BMI is a person’s body weight (in kilograms) divided by the square of height (in meters). Weight was measured with the individual standing on an electronic weighing scale (150 kg capacity, 50 gram accuracy). Height was measured using a professional portable stadiometer, 0.1 cm accuracy, where the individual was standing straight with heels together on the base. BMI of the participants was classified according to the cutoff points for the older adults, as recommended by the Ministry of Health⁹9 Brasil. Ministério da Saude (MS). Orientações para a coleta e análise de dados antropométricos em serviços de saúde: Norma Técnica do Sistema de Vigilância Alimentar e Nutricional - SISVAN. Brasília: MS; 2011., that is, up to 22 kg/m²: low weight, between 22 and 26.99 kg/m²: eutrophic, 27 kg/m² or more: overweight.

Waist circumference was measured with a non-extendable measuring tape located at the midpoint between the iliac crest and the last rib. Risk for cardiovascular disease (CVD) was considered when the male participants presented 102 centimeters or more and 88 centimeters or more for female participants¹⁰10 World Heath Organization (WHO). WHO 1995 Physical status. Use and anthropometry. World Health Organization technical report series 1995..

Regarding physical activity, individuals were considered active when they reported at least 150 minutes of moderate intensity aerobic physical activity or 75 minutes of vigorous intensity aerobic physical throughout the week¹¹11 World Heath Organization (WHO). Global recommendations on physical activity for health. Geneva: WHO; 2010;.

For the assessment of smoking, individuals answered “yes” if they were currently smokers, “no” if they had never smoked, or if they were former smokers.

Skin type was assessed using the Fitzpatrick scale¹²12 Fitzpatrick TB. The Validity and Practicality of Sun-Reactive Skin Types I Through VI. Arch Dermatol 1988; 124(6):869-871., which defines scores to skin phototypes: from 1 to 6, where type 1 is the palest skin which always burns and never tans, and type 6 is the darkest skin which never burns and always tans when exposed to the sun (the participant pointed to a printed picture matching the color of his/her skin).

Statistical analysis

For the statistical analysis of the study variables, distributions of relative frequencies, mean values and standard deviation were estimated for continuous variables, and proportions were estimated for categorical variables. Differences between groups were estimated using the Mann-Whitney test after analyzing the normality of distributions, and x²2 Mendes MM, Hart KH, Botelho PB, Lanham-New SA. Vitamin D status in the tropics: Is sunlight exposure the main determinant? Nutr Bull 2018; 43(4):428-434. test was used to analyze differences between categorical variables. Variables with p value < 0.20 in simple association were selected to calculate crude and age-adjusted odds ratios, with different models for general, physical and health characteristics and sun exposure habits, but the variables with p value < 0.05 remained in the tables. The critical level was p < 0.05. The analyses were performed in Stata version 14.

Results

All 533 participants included in the study had a mean age of 69.6 ± 6.7 years, with predominance of female participants. Most participants were married (60.4%), white (54.4%), had less than 8 years of education (71.8%) and income of two or more minimum wages (70.5%). When analyzing the nutritional status indicators, we found mean BMI of 28.9 ± 5.4 kg/m², with most participants classified as overweight (60.4%) and at risk for CVD according to the waist circumference assessment (58.7%). Regarding health-related behaviors, 58.7% had never smoked and 64.4% were inactive smokers (Table 1).

The mean serum concentration of 25-OHD was 28.3 ± 9.2 ng/mL, and the prevalence of insufficiency was 64.5%, higher among female participants and those who self-reported as black/brown/indigenous/yellow/unreported, categorized as “other” ethnicity (Table 1). No difference was observed in age group, marital status, income, education, those with paid work, and head of household. Table 1 shows higher prevalence of vitamin D insufficiency among individuals classified as underweight and those with a waist circumference measurement above the limits of risk for developing CVD.

Regarding health data of participants, most of them reported medical diagnosis of three or more diseases - the most prevalent disorders were: hypertension (61.9%), spine issues (50.5%), rheumatism (43.1%), diabetes (27.6%), depression (27.6%), and CVD (23.6%). No significant difference was found when associating these diseases and vitamin D insufficiency or grouping individuals by the number of pre-existing diseases.

In the evaluation of sex- and age-adjusted logistic regression of general, physical and health characteristics of participants, those of “other” ethnicity, low weight and high waist circumference were more likely to have vitamin D insufficiency (Table 2).

Table 3 shows that most participants self-reported daily sun exposure while commuting (e.g., going to the market, drugstore, etc.) without sunscreen. They also reported exposure of less than 3 times during the week, for less than 15 minutes on average, between 9 am and 3 pm, with hands, arms and face as their more frequently exposed body parts. Every participant could report more than one exposure habit, time and exposed body parts. According to the Fitzpatrick scale, the predominant skin phototype was type 4, followed by types 2 and 3.

The proportion of vitamin D sufficiency was higher among participants reporting sun exposure during leisure and physical activities (p = 0.018 and p = 0.010, respectively). A difference was also observed between participants who reported exposure between 9 am and 3 pm (p = 0.032) and exposure of hands and arms (p = 0.046) (Table 3).

In the evaluation of sex- and age-adjusted logistic regression of sun exposure habits of participants, a negative association was observed between vitamin D insufficiency and individuals reporting exposure habits during leisure activities, daily commuting, practice of physical activities, exposure between 9 am and 3 pm, and hands, arms and as their more frequently exposed body parts (Table 4).

Discussion

A high prevalence of vitamin D insufficiency was reported among the older adults participants evaluated (64.5%), with sex, ethnicity, body composition and some habits of sun exposure associated with vitamin D insufficiency.

Regarding the high prevalence of vitamin D insufficiency, similar indices were found in another study conducted with the same population profile in the country⁴4 Santos CS, Bessa TA, Xavier AJ. Fatores associados à demência em idosos. Cien Saude Colet 2020; 25(2):603-611.^,1313 Saraiva GL, Cendoroglo MS, Ramos LR, Araújo LM, Vieira JG, Kunii I, Hayashi LF, Corrêa MP, Lazaretti-Castro M. Influence of ultraviolet radiation on the production of 25 hydroxyvitamin D in the elderly population in the city of São Paulo (23° 34'S), Brazil. Osteoporos Int 2005; 16(12):1649-1654.^,1414 Saraiva GL, Cendoroglo MS, Ramos LR, Araújo LMQ, Vieira JGH, Maeda SS, Borba VZC, Kunii I, Hayashi LF, Lazaretti-Castro M. Prevalência da deficiência, insuficiência de vitamina D e hiperparatiroidismo secundário em idosos institucionalizados e moradores na comunidade da cidade de São Paulo, Brasil. Arq Bras Endocrinol Metabol 2007; 51(3):437-442., while a study performed with 81 older adults in Ribeirão Preto, São Paulo¹⁵15 Cicilini AL, Singling MV, Silva KA, Ramos APP. Níveis séricos de 25-hidroxivitamina D em idosos com Diabetes mellitus tipo 2 atendidos em um Hospital Universitário de Ribeirão Preto (SP). Rev Ciências da Saúde da Amaz 2019; 1:3-24., found a higher prevalence (76.5%) of vitamin D insufficiency, with serum 25-OHD levels of 24.63 ± 7.89 ng/mL.

Brazil has a geographic location that provides good availability of ultraviolet rays (UVB) throughout the year, which allows exposure to sunlight and cutaneous synthesis of vitamin D at proper concentrations in most seasons of the year. However, studies have reported high prevalence of vitamin D insufficiency and deficiency. This paradox can be partly explained by the concern about preventing high levels of sun exposure, regardless of the concentration of solar radiation, a precaution that leads the population to be less exposed to the sun or use physical/chemical barriers (clothes, hats, sunscreen), thus increasing the prevalence of inadequate levels of vitamin D¹⁶16 Pereira-Santos M, Santos JYG, Carvalho GQ, Santos DB, Oliveira AM. Epidemiology of vitamin D insufficiency and deficiency in a population in a sunny country: Geospatial meta-analysis in Brazil. Crit Rev Food Sci Nutr 2019; 59:2102-2109..

Specifically in relation to sex, the female participants had lower mean values and higher prevalence of insufficiency (adjusted OR 2.54; p < 0.001). A study that evaluated 359 older adults in Teresina, Piauí,⁷7 Oliveira GBVP, Silva Júnior FL, Oliveira MCB, Carvalho CMRG. Relação dos índices antropométricos e vitamina D com o desempenho funcional em idosos TT - Relationship of anthropometric indices and vitamin D with functional performance in elderly. Estud interdiscip Envelhec 2018; 23(1):43-59. found even lower mean values when analyzing serum levels (22.51 ± 8.03 ng/mL), which were also lower among female participants. Several studies¹⁷17 Dawson-Hughes B, Harris SS, Dallal GE. Plasma calcidiol, season, and serum parathyroid hormone concentrations in healthy elderly men and women. Am J Clin Nutr 1997; 65(1):67-71.

18 Carnevale V, Modoni S, Pileri M, Di Giorgio A, Chiodini I, Minisola S, Vieth R, Scillitani A. Longitudinal evaluation of vitamin D status in healthy subjects from southern Italy: Seasonal and gender differences. Osteoporos Int 2001; 12(12):1026-1230.^-1919 Maeda SS, Kunii IS, Hayashi LF, Lazaretti-Castro M. Increases in summer serum 25-hydroxyvitamin D (25OHD) concentrations in elderly subjects in São Paulo, Brazil vary with age, gender and ethnicity. BMC Endocr Disord 2010; 10:12. show that women are more likely to have lower levels of 25-OHD than men, particularly due to the type of clothes and sun protection behavior of women, which makes cutaneous synthesis of vitamin D less efficient²⁰20 Nimitphong H, Holick MF. Vitamin D status and sun exposure in Southeast Asia. Dermatoendocrinol 2013; 5(1):34-37..

Regarding skin color, reduced efficiency of vitamin D synthesis in people with dark skin is well described in the literature, to the greater amount of melanin, which acts as a natural sunscreen⁵5 Moreira CA, Ferreira CEDS, Madeira M, Silva BCC, Maeda SS, Batista MC, Bandeira F, Borba VZC, Lazaretti-Castro M. Reference values of 25-hydroxyvitamin D revisited: a position statement from the Brazilian Society of Endocrinology and Metabolism (SBEM) and the Brazilian Society of Clinical Pathology/Laboratory Medicine (SBPC). Arch Endocrinol Metab 2020; 64(4):462-478.. It explains the higher prevalence of vitamin D insufficiency found among individuals reporting more pigmented skin color ethnicities.

The association between overweight and vitamin D insufficiency is also well described in the literature²¹21 Snijder MB, van Dam RM, Visser M, Deeg DJ, Dekker JM, Bouter LM, Seidell JC, Lips P. Adiposity in relation to vitamin D status and parathyroid hormone levels: A population-based study in older men and women. J Clin Endocrinol Metab 2005; 90(7):4119-4123.

22 Scragg R, Camargo CA. Frequency of leisure-time physical activity and serum 25-hydroxyvitamin D levels in the US population: Results from the third national health and nutrition examination survey. Am J Epidemiol 2008; 168(6):577-586.

23 Lagunova Z, Porojnicu LC, Lindberg F, Hexeberg S, Moan J. The dependency of vitamin D status on body mass index, gender, age and season. In: Anticancer Research. 2009. p. 3713-20.

24 Jorde R, Sneve M, Emaus N, Figenschau Y, Grimnes G. Cross-sectional and longitudinal relation between serum 25-hydroxyvitamin D and body mass index: The Tromsø study. Eur J Nutr 2010; 49(7):401-407.

25 Yoshimura N, Muraki S, Oka H, Morita M, Yamada H, Tanaka S, Kawaguchi H, Nakamura K, Akune T. Profiles of vitamin D insufficiency and deficiency in Japanese men and women: association with biological, environmental, and nutritional factors and coexisting disorders: the ROAD study. Osteoporos Int 2013; 24(11):2775-2787.

26 Nakamura K, Kitamura K, Takachi R, Saito T, Kobayashi R, Oshiki R, Watanabe Y, Tsugane S, Sasaki A, Yamazaki O. Impact of demographic, environmental, and lifestyle factors on vitamin D sufficiency in 9084 Japanese adults. Bone 2015; 74:10-17.^-2727 Mansouri M, Abasi R, Nasiri M, Sharifi F, Vesaly S, Sadeghi O, Rahimi N, Sharif NA. Association of vitamin D status with metabolic syndrome and its components: a cross-sectional study in a population of high educated Iranian adults. Diabetes Metab Syndr Clin Res Rev 2018; 12(3):393-398.. It can be explained by biological factors, since obesity decreases the bioavailability of vitamin D obtained by cutaneous synthesis, as vitamin D tends to be deposited on adipose tissue, changes the regulation of PTH and hepatic synthesis of 25-OHD, and involves lifestyle factors, such as lower intake of vitamin D in the diet of obese people²⁸28 Jääskeläinen T, Knekt P, Marniemi J, Sares-Jäske L, Männistö S, Heliövaara M, Järvinen R. Vitamin D status is associated with sociodemographic factors, lifestyle and metabolic health. Eur J Nutr 2013; 52(2):513-525.. Although this study did not find an association with overweight according to the BMI classification, after an adjusted regression analysis, this association was observed with increased waist circumference (adjusted OR 1.57; p = 0.018). A study conducted by Snijder et al.²¹21 Snijder MB, van Dam RM, Visser M, Deeg DJ, Dekker JM, Bouter LM, Seidell JC, Lips P. Adiposity in relation to vitamin D status and parathyroid hormone levels: A population-based study in older men and women. J Clin Endocrinol Metab 2005; 90(7):4119-4123. in Amsterdam with 453 older adults found an association between low levels of 25-OHD and high waist circumference. This characteristic is an important factor, as it seems to make an individual more susceptible to lower levels of 25-OHD²⁹29 Gheno FP, Cabral MMS, Schirmer CL, Dallepiane LB, Bos AJG. Diet quality and nutritional status in Southern Brazilian oldest old. Nutr Food Toxicol. 2017;1:2.^,3030 Matchar DB, Chei CL, Yin ZX, Koh V, Chakraborty B, Shi XM, Zeng Y. Vitamin D levels and the risk of cognitive decline in Chinese elderly people: the Chinese Longitudinal Healthy Longevity Survey. J Gerontol A Biol Sci Med Sci 2016; 71(10):1363-1368..

On the other hand, we found a strong association between vitamin D insufficiency and low weight (adjusted OR 2.56; p = 0.023). A study conducted by Cabral³¹31 Cabral MMS. Vitamina D em longevos, qual o fator mais importante: ingesta alimentar ou exposição solar? [Tese]. Porto Alegre: Pontifícia Universidade Católica do Rio Grande do Sul; 2017. that assessed older adults in Porto Alegre, Rio Grande do Sul, also found deficient levels of 25-OHD with higher prevalence among thin or malnourished older adults, suggesting vitamin D deficiency is associated with nutritional risk and malnutrition.

Several studies show higher serum levels of 25-OHD among individuals who practice physical activities²¹21 Snijder MB, van Dam RM, Visser M, Deeg DJ, Dekker JM, Bouter LM, Seidell JC, Lips P. Adiposity in relation to vitamin D status and parathyroid hormone levels: A population-based study in older men and women. J Clin Endocrinol Metab 2005; 90(7):4119-4123.^,2828 Jääskeläinen T, Knekt P, Marniemi J, Sares-Jäske L, Männistö S, Heliövaara M, Järvinen R. Vitamin D status is associated with sociodemographic factors, lifestyle and metabolic health. Eur J Nutr 2013; 52(2):513-525.^,3232 Looker AC. Do body fat and exercise modulate vitamin D status? Nutr Rev 2007; 65(8 Pt. 2):S124-S126.^,3333 Hintzpeter B, Mensink GBM, Thierfelder W, Müller MJ, Scheidt-Nave C. Vitamin D status and health correlates among German adults. Eur J Clin Nutr 2008; 62(9):1079-1089.. This characteristic is even more accentuated when this practice is performed outdoors¹⁹19 Maeda SS, Kunii IS, Hayashi LF, Lazaretti-Castro M. Increases in summer serum 25-hydroxyvitamin D (25OHD) concentrations in elderly subjects in São Paulo, Brazil vary with age, gender and ethnicity. BMC Endocr Disord 2010; 10:12.. In this study, we found no significant difference between groups in terms of active individuals. However, individuals reporting sun exposure during physical activity showed a lower prevalence of vitamin D insufficiency.

Among the diseases reported by participants, although the relationship between hypovitaminosis D and various diseases such as diabetes, cardiovascular diseases, hypertension, cancer, osteoporosis, depression, among others³⁴34 Caristia S, Filigheddu N, Barone-Adesi F, Sarro A, Testa T, Magnani C, Aimaretti G, Faggiano F, Marzullo P. Vitamin D as a biomarker of ill health among the over-50s: a systematic review of cohort studies. Nutrients 2019;11., is well described in the literature, no association was observed between these diseases and vitamin D insufficiency. Also, no significant difference was found regarding the number of diseases reported by participants.

A correctly applied sunscreen with sun protection factor (SPF) 30 is presumed to reduce by 95% to 99% the skin ability to produce vitamin D³⁵35 Hossein-Nezhad A, Holick MF. Vitamin D for health: a global perspective. In: Mayo Clinic Proceedings. 2013. p. 720-755.. Despite that, we found no significant difference for vitamin D insufficiency between individuals who reported using sunscreen and those who did not have such habit. A similar result was reported by Maeda et al.¹⁹19 Maeda SS, Kunii IS, Hayashi LF, Lazaretti-Castro M. Increases in summer serum 25-hydroxyvitamin D (25OHD) concentrations in elderly subjects in São Paulo, Brazil vary with age, gender and ethnicity. BMC Endocr Disord 2010; 10:12. for using sunscreen or not. On the other hand, in a study conducted by Cabral³¹31 Cabral MMS. Vitamina D em longevos, qual o fator mais importante: ingesta alimentar ou exposição solar? [Tese]. Porto Alegre: Pontifícia Universidade Católica do Rio Grande do Sul; 2017., sunscreen was significantly associated with proper levels of 25-OHD, a fact that, according to the author, can be explained by a possible application of insufficient or uneven sunscreen.

The efficiency of sun exposure in vitamin D synthesis depends on the use of sunscreen and other factors, such as latitude, season of the year, air pollution, skin pigmentation, and age³⁶36 Brouwer-Brolsma EM, Vaes AMM, van der Zwaluw NL, van Wijngaarden JP, Swart KMA, Ham AC, van Dijk SC, Enneman AW, Sohl E, van Schoor NM, van der Velde N, Uitterlinden AG, Lips P, Feskens EJM, Dhonukshe-Rutten RAM, de Groot LCPGM. Relative importance of summer sun exposure, vitamin D intake, and genes to vitamin D status in Dutch older adults: The B-PROOF study. J Steroid Biochem Mol Biol 2016; 164:168-176.. For white adults, it is recommended to expose arms and legs to the sun (which represent 25% of the body surface when wearing shorts and a short-sleeve shirt or blouse) for about 5 to 15 minutes, between 9 am and 3 pm, three times a week (depending on the latitude, season of the year, and skin pigmentation), which would be sufficient for the production of vitamin D required. However, among the older adults, cutaneous synthesis is reduced to around 25% of the capacity of a 20-year-old person³⁷37 Holick MF. Vitamin D: a D-lightful solution for health. In: Journal of Investigative Medicine. 2011. p. 872-880..

Despite the reduced capacity of vitamin D photoproduction among older people, Brouwer-Brolsma et al.³⁶36 Brouwer-Brolsma EM, Vaes AMM, van der Zwaluw NL, van Wijngaarden JP, Swart KMA, Ham AC, van Dijk SC, Enneman AW, Sohl E, van Schoor NM, van der Velde N, Uitterlinden AG, Lips P, Feskens EJM, Dhonukshe-Rutten RAM, de Groot LCPGM. Relative importance of summer sun exposure, vitamin D intake, and genes to vitamin D status in Dutch older adults: The B-PROOF study. J Steroid Biochem Mol Biol 2016; 164:168-176. observed significant associations between habitual sun exposure and 25-OHD in this population. Data from a study conducted by Maeda et al.¹⁹19 Maeda SS, Kunii IS, Hayashi LF, Lazaretti-Castro M. Increases in summer serum 25-hydroxyvitamin D (25OHD) concentrations in elderly subjects in São Paulo, Brazil vary with age, gender and ethnicity. BMC Endocr Disord 2010; 10:12. suggest the amount of UVB radiation at the latitude of the city of São Paulo, SP, is sufficient for proper production of vitamin D, even for the older population, as long as they have minimal exposure. However, it should be noted that sun exposure is not enough to compensate for vitamin D insufficiency or deficiency³⁸38 Lee YM, Kim SA, Lee DH. Can current recommendations on sun exposure sufficiently increase serum vitamin D level?: One-month randomized clinical trial. J Korean Med Sci. 2020; 35:8.. Data obtained in this study related to sun exposure agree with literature findings. Lower proportions of vitamin D insufficiency were observed among individuals who reported sun exposure during leisure activities and physical activities (p = 0.018 and p = 0.010, respectively), and between 9 am and 3 pm, the peak period of solar radiation (p = 0.032).

Our study limitation refers to the fact that it used the older adults participants accounts as a parameter to assess habitual sun exposure, and this information can be underestimated or overestimated. Also, data were not analyzed separately by season. However, data collection was not performed during the winter and, considering the incidence of UVB rays are similar during spring, summer and autumn at the latitude in question, we consider these findings to be relevant. Another study limitation is that the individuals were volunteers, and many of them came from health groups from the primary health care system in the municipalities, including outdoor physical activity groups, causing the bias of “healthy participant/volunteer participant,” a fact that may have partially influenced the results. However, this is a common limitation in population studies where participants are invited in out-of-home interviews, as volunteers are usually more interested in health-related issues.

One of the strengths of our study is the assessment of a sample of older population assisted by primary health care services in the cities of Limeira, Piracicaba, and Campinas, and the investigation conducted in the same study of various factors that can be associated with vitamin D insufficiency in this vulnerable age group.

The results obtained show the relevance of the impact of factors like sex, ethnicity, body composition, physical activity, and sun exposure habits on the prevalence of inadequate levels of vitamin D among older adults, and the importance of considering these factors as vitamin D insufficiency predictors in this population, mainly as a primary care tool. The assessment of these factors is a simple, low-cost and non-invasive measure that can contribute to the early identification of vitamin D insufficiency, enabling actions and strategies to prevent and control this condition, which has become increasingly prevalent in Brazil and in the world.

Acknowledgment

The authors thank Espaço da Escrita - Pró-Reitoria de Pesquisa (UNICAMP) for the language services provided. Also the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq), Pró-Reitoria de Pesquisa da Unicamp and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), which financed the research (CNPq 408262/2007-6, FAEPEX 2854/18 and 3150/19, CAPES financing code 001).

References

Publication Dates

History