Vitamin D insufficiency and frailty syndrome in older adults living in a Northern Taiwan community
Introduction
Frailty can be described as “a biological syndrome of decreased reserve (energy, physical ability, cognition, health) and resistance to stressors, resulting from cumulative declines across multiple physiological systems and causing vulnerability to adverse outcomes” (Fried et al., 2001). Older people with frailty are at increased risk for adverse health outcomes, including lost functional abilities and frequent hospitalizations (Rockwood et al., 1999; Fried et al., 2001). It is widely accepted that frailty is multidimensional, heterogeneous, and unstable, thus distinguishing it from disability or aging alone (Hogan et al., 2003). However, many instruments have been developed to measure frailty without a unifying classification system (Fried et al., 2001; Rockwood et al., 2005; Rolfson et al., 2006; Abellan van Kan et al., 2008).
The instrument proposed by Fried et al. (2001), the FFI, following the Cardiovascular Health Study, classified subjects into three categories based on five indicators. It is one of the most widely used instruments in the research setting with emphasis on the physical domain (Abellan van Kan et al., 2008). Other instruments measure deficiencies in other areas such as cognition, burden of medical illness, and quality of life. For example, the EFS classifies subjects into five categories based on 10 domains (11 indicators) (Rolfson et al., 2006; Abellan van Kan et al., 2008).
Vitamin D, hydroxylated in the liver into 25-hydroxyvitamin D [25(OH)D], increases the absorption of calcium and phosphate needed for mineralization of the skeleton (Lips, 2001). Low 25(OH)D increases the risk of falls (Bischoff-Ferrari et al., 2004, Bischoff-Ferrari et al., 2005; Snijder et al., 2006), fractures (Bischoff-Ferrari et al., 2005), bone pain (Atherton et al., 2009; Lips, 2001; Mascarenhas and Mobarhan, 2004; Bischoff-Ferrari et al., 2005), muscle weakness (Bischoff-Ferrari et al., 2004; Gerdhem et al., 2005), sarcopenia (Visser et al., 2003), and disability (Lips, 2001). Recent studies have suggested that vitamin D may play some role in immunomodulation, infectious disease prevention, and psychiatric disorders (particularly depression) (Adams and Hewison, 2008; Hoogendijk et al., 2008). Low 25(OH)D levels are common in the elderly due to decreased vitamin synthesis in the skin, insufficient sunlight exposure, and deficient dietary supplementation (Holick et al., 1989; Kinyamu et al., 1998). Though a few investigators have studied the association between low vitamin D levels and frailty, most have emphasized the physical aspect (Puts et al., 2005; Shardell et al., 2009). It is not certain whether the finding would be replicable in other studies assessing frailty differently. The association between vitamin D insufficiency and frailty using both the FFI and the EFS was explored.
Section snippets
Subjects
The target population was community-dwelling older adults aged 65–79 years in the 31 census areas of Tofun town (roughly 7,000 people, 7.1% of the whole population). Details regarding design and sampling have been described elsewhere (Chan, D.C., Tsou, H.H., Chen, C.Y., Hsiung, C., Kuo, K.N. A pilot randomised controlled trial of integrated care model on geriatric frailty. Unpublished results). Briefly, 2,900 population-representative random samples were screened through a two-stage process to
Baseline characteristics
The distributions of baseline characteristics for the entire study population (n = 215) are listed in Table 1. The mean age was 71.1±3.9 years, with 128 (59.5%) female. The study cohort had an average of 3.4±2.0 comorbid conditions. The mean MMSE score was 25.1±3.7, and the mean BI score was 98.5±4.3. The mean 25(OH)D level was 39.9±25.9 ng/ml, with 66 (31%) under 20 ng/ml (vitamin D insufficiency).
Distribution of baseline characteristics among subjects with different frailty statuses
Using the FFI, 75 (34.9%) subjects were classified as robust, 119 (55.3%) as pre-frail, and 21
Discussion
The present study found that there was a strong dose-response relationship between vitamin D insufficiency and frailty using the FFI. The association may be attenuated using the EFS assessment. To the best of our knowledge, this is the first report to examine the association between vitamin D insufficiency and frailty using different frailty assessment instruments.
In the present study, the mean serum 25(OH)D level was 39.9 ng/ml, which was in the normal range (Lips, 2001). Studies by Lee and
Conclusion
The prevalence of vitamin D insufficiency was high among this population. There was a strong association between vitamin D insufficiency and frailty index. Vitamin D insufficiency is easily treated with adequate supplements. Future clinical trials may consider the treatment of vitamin D insufficiency to improve frailty syndrome in older adults in order to prevent the progression to functional disability and worse outcomes.
Conflict of interest statement
None.
Acknowledgements
This study was supported by the 97_HDSP08_020 grant “Interventional study of Geriatric Frailty, Osteoporosis, and Depression in a Community Based Randomized Trial” from the National Health Research Institutes, Zhunan, Taiwan.
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