Abstract
BackgroundVitamin D is important in bone health and its relationship with osteoarthritis has recently been reported. Both vitamin D deficiency and knee osteoarthritis are age dependent and are known to affect quality of life (QOL) in older populations. In this study, we aimed to determine the association between vitamin D status and health-related quality of life (HRQOL) in an older Korean population with knee osteoarthritis.MethodsA total of 2,165 participants aged ≥50 years with radiographic knee osteoarthritis defined as Kellgren-Lawrence (KL) grade ≥2 were selected from data from the 5th Korean National Health and Nutrition Examination Survey (KNHANES V), a representative cross-sectional nationwide survey conducted in 2010–2011. They stratified into two levels by vitamin D status (deficiency <10 ng/dL and normal ≥10 ng/dL). HRQOL was measured using the EuroQOL visual analogue scale (EQ-VAS) and the five dimensions and summary index of the EuroQOL-5 dimension (EQ-5D).ResultsThe vitamin D deficiency group was more likely to report problems with mobility, self-care, and usual activities. Vitamin D deficiency was significantly associated with poor HRQOL indicated by the lowest quartile of EQ-VAS (unadjusted odds ratio [OR] =1.832, p = 0.006) and the lowest quartile of the EQ-5D index (unadjusted OR = 1.992, p = 0.003). Theses associations of vitamin D status with EQ-VAS and EQ-5D index were maintained after adjustment for age and sex (Model 1: OR = 1.677, p = 0.022 and OR = 1.701, p = 0.021, respectively). The significant associations of vitamin D status with EQ-VAS were maintained after adjustment for other possible covariates (Model 3: OR = 1.562, p = 0.044). Also, a trend of associations between vitamin D status and EQ-5D index were shown after adjustment for other covariates (Model3: OR = 1.681, p = 0.056).ConclusionThis is the first study to reveal that vitamin D status is independently associated with HRQOL in an older Korean population with knee osteoarthritis. Our results suggest that the maintenance of sufficient vitamin D status may be important to prevent QOL decline in older populations with knee osteoarthritis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12955-015-0245-1) contains supplementary material, which is available to authorized users.
Highlights
Vitamin D is important in bone health and its relationship with osteoarthritis has recently been reported
Vitamin D deficiency group showed a significant association with poor health-related quality of life (HRQOL) indices such as EuroQOL visual analogue scale (EQ-VAS) (OR = 2.360, p = 0.024 in Model 1, odds ratios (ORs) = 2.291, p = 0.035 in Model 2, and OR = 1.934, p = 0.137 in Model 3) and EuroQOL-5 dimension (EQ-5D) index (OR =2.390, p = 0.031 in Model 1, OR = 2.324, p = 0.043 in Model 2, and OR = 2.803, p = 0.021 in Model 3) when we re-analyzed after excluding participants comorbid with chronic diseases to control the impact of other chronic diseases completely (Table 4). Their sample size were 903(95.3%) for vitamin D normal group and 46(4.7%) for vitamin D deficiency group, respectively. In this nationwide cross-sectional study, we examined a possible association between vitamin D status and HRQOL using a representative sample of an older Korean population (≥50 years) with radiographically confirmed knee osteoarthritis
We found that vitamin D deficiency was associated with poor quality of life (QOL) independently of other covariates and possible confounders, including age, sex, Body mass index (BMI), waist circumference, education, income, residence, exercise, marital status, smoking status, comorbidity of chronic disease, and KL grade, in an older Korean population with knee osteoarthritis
Summary
Vitamin D is important in bone health and its relationship with osteoarthritis has recently been reported Both vitamin D deficiency and knee osteoarthritis are age dependent and are known to affect quality of life (QOL) in older populations. The precise mechanisms remain unknown, vitamin D has recently been shown to be linked with various extraskeletal diseases, such as cardiovascular diseases, diabetes, cancer, auto-immune diseases, and depressive disorders [5,6,7] Because these chronic pathologic conditions are known to affect quality of life (QOL), vitamin D deficiency may be related to QOL in old people. Recent studies demonstrated the association between vitamin D and health-related QOL (HRQOL) in general older population [8,9] These results were inconsistent in other groups of subjects with different medical conditions [10,11]. These inconsistencies resulted from the differences in methodologies, the association of vitamin D with specific diseases, study design, and study populations [12]
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