Vitamin D Status of Older Adults with Dynapenic Obesity in Ecuador.

Abstract

To the Editor: Muscle strength decreases with age, and fat mass increases.1 Cross-sectional and longitudinal studies have reported that the combined effect of obesity and low muscle strength in older adults, a condition defined as dynapenic obesity, increases the risk of mobility disability, functional limitations, falls, hospitalizations, and mortality.2-4 Lower 25-hydroxyvitamin D (25(OH)D) concentrations have been associated with loss of muscle strength and higher body fat in older adults.4, 5 Consequently, it has been proposed that vitamin D supplementation may be beneficial for treating dynapenia with or without obesity.6 Nevertheless, data regarding 25(OH)D concentrations in older adults with dynapenic obesity are scarce. Thus, this study aimed to examine the prevalence of 25(OH)D deficiency in older Ecuadorians according to their dynapenia and obesity status. It was hypothesized that older adults with dynapenic obesity would be more likely to be deficient in 25(OH)D than those with obesity alone, dynapenia alone, or neither dynapenia nor obesity. The present study was based on data from the first National Health, Wellbeing, and Aging Survey.7 Participants self-reported their race and region of residence. Literacy was defined as an affirmative answer to the question “Can you write and read a message.” Smoking status was classified as current, former, and never. Subjects were considered to consume dairy products if they answered the question “Do you consume milk, cheese, or yogurt at least once per day?” affirmatively. Vigorous and regular physical activity was evaluated according to the question, “Do you exercise, such as jogging, dancing, or performing rigorous physical activity at least three times weekly for the past year? Body mass index (BMI) was calculated, and obesity was defined as a BMI of 30 kg/m2 or greater. Grip strength of the dominant hand was measured using a standard handheld dynamometer, and the better of two trials was reported in the present analysis. Although there is no general consensus on the definition of low muscle strength, subjects in the lowest grip strength sex-specific tertile were considered to have dynapenia. Participants (N = 2,047; age: mean 70.3 ± 7.8, range 60–102) were grouped into four categories according to grip strength and obesity status: nondynapenia nonobesity, obesity alone, dynapenia alone, and dynapenic obesity. Serum 25(OH)D was measured using liquid chromatography (NetLab, Quito, Ecuador), and 25(OH)D deficiency was defined as less than 20 ng/mL.8 Analysis of variance was used to compare 25(OH)D concentrations and the chi-square test to compare the proportion of 25(OH)D deficiency according to group. Sex-specific multivariate logistic regression models were used to evaluate the associations between obesity, dynapenia, and 25(OH)D deficiency. The prevalence of 25(OH)D deficiency was 29.1% (95% confidence interval (CI) = 25.8–32.6) in women and 11.3% (95% CI = 9.1–13.9) in men. The prevalence of obesity was significantly higher in women (Table 1), whereas men had greater prevalence of low muscle strength. Dynapenic obesity was present in 6.8% (95% CI = 5.1–9.0) of women and 2.4% (95% CI = 1.5–3.7) of menl up to 38.1% (95% CI = 37.5–38.5) of women and 23.5% (95% CI = 22.7–24.3) of men with this phenotype had evidence of 25(OH)D deficiency. After adjustment for potential confounders, the odds of women with dynapenic obesity having 25(OH)D deficiency were 1.9 as high as those of their counterparts with neither dynapenia nor obesity and those of men were 2.2 times as high. Older men and women with dynapenic obesity had considerably higher 25(OH)D deficiency prevalence rates than those with obesity alone, dynapenia alone, and neither of these conditions. Moreover, it appears that obesity and dynapenia were characteristics independently associated with 25(OH)D deficiency in older Ecuadorians. The strong relationship between dynapenic obesity and 25(OH)D deficiency persisted even after adjustment for variables previously reported to be associated with high 25(OH)D deficiency prevalence rates in older adults in Ecuador.9 The present findings are consistent with results from a previous study that found low 25(OH)D concentrations in older adults with dynapenic abdominal obesity.3 Similarly, it was reported that greater visceral fat and lower muscle mass were associated with lower 25(OH)D levels in elderly Korean men.10 The present study has some limitations. First, the cross-sectional relationship between 25(OH)D deficiency and dynapenic obesity does not imply causation. For instance, the higher prevalence of 25(OH)D deficiency in older adults with dynapenic obesity may have been the result of inadequate outdoor activities and sunlight exposure. Second, vitamin D dietary intake and vitamin D supplements were not assessed in the survey. In conclusion, older Ecuadorian adults with dynapenic obesity had considerably higher 25(OH)D deficiency prevalence rates than those without. The present findings merit further prospective studies to examine the efficacy of vitamin D supplementation in older adults with these characteristics. Conflict of Interest: None. Author Contributions: Orces: study concept, data acquisition, data analysis and interpretation, preparation of manuscript. Weisson: data interpretation, preparation of manuscript. Sponsor's Role: No sponsors.