Serum levels of vitamin D, sunlight exposure, and knee cartilage loss in older adults: The Tasmanian older adult cohort study

Abstract

Objective. To determine the associations between serum levels of vitamin D, sunlight exposure, and knee cartilage loss cross-sectionally and longitudinally in older adults.Methods. A total of 880 randomly selected subjects (mean age 61 years [range 51-79 years], 50% women) were studied at baseline, and 353 of these subjects were studied 2.9 years later. Serum levels of 25-hydroxyvitamin D (25[OH]D) were assessed by radioimmunoassay, and sunlight exposure was assessed by questionnaire. T1-weighted fat-suppressed magnetic resonance imaging (MRI) of the right knee was performed to determine knee cartilage volume and defects. Knee radiographic osteoarthritis (OA) and knee pain were also assessed. Results. The mean 25(OH)D serum level was 52.8 nmoles/liter at baseline (range 13-119 nmoles/liter). Winter sunlight exposure and serum 25(OH)D levelwere both positively associated with medial and lateral tibial cartilage volume, and a serum 25(OH)D level <50 nmoles/liter was associated with increased medial tibiofemoral joint space narrowing (all P < 0.05). Longitudinally, baseline serum 25(OH)D level predicted change in both medial and lateral tibial cartilage volume (␤ ‫؍‬ ؉0.04% per annum per nmole/liter for both; P < 0.05), and change in serum 25(OH)D level was positively associated with change in medial tibial cartilage volume. These associations were consistent in subjects with radiographic OA and knee pain and/or in women, but not in men or in subjects without radiographic OA or knee pain.Conclusion. Sunlight exposure and serum 25(OH)D levels are both associated with decreased knee cartilage loss (assessed by radiograph or MRI). This is best observed using the whole range of 25(OH)D levels rather than predefined cut points and implies that achieving vitamin D sufficiency may prevent and/or retard cartilage loss in knee OA.Both osteoarthritis (OA) and vitamin D insufficiency are common health conditions in older people. Approximately 25% of people age Ͼ55 years have had knee pain on most days in a month in the past year, of which about half have radiographic knee OA and thus are considered to have symptomatic OA (1). Furthermore, it has been estimated that 1 billion people worldwide have vitamin D deficiency or insufficiency (2,3). Vitamin D insufficiency has been linked with osteoporosis and fractures both in older women and in older men (2); however, the role of vitamin D insufficiency in the pathogenesis of OA is controversial.Preliminary evidence suggests that vitamin D has direct effects on chondrocytes in OA cartilage, and

Association between serum vitamin D deficiency and knee osteoarthritis

“…Up to now most studies addressed the association between OA and serum 25-OHD in longitudinal studies [5,6,[14][15][16][17]. No study has yet compared serum 25-OHD levels between OA patients and controls.…”

“…Inadequate levels of serum 25-OHD in patients with knee OA is of major concern. Since at low tissue concentrations of serum vitamin D bone response to pathophysiological processes is not optimal, vitamin D deficiency provides a susceptible background for OA progression [5][6][7]14].…”

“…Vitamin D status influences the incidence and progression of knee OA [5]. Sunlight exposure and serum 25-OHD levels are both associated with decreased knee cartilage loss [6]. In serum 25-OHD deficient men the prevalence of OA was two times greater than those with sufficient levels [7].…”

Targeting subchondral bone for treating osteoarthritis: what is the evidence?

“…However, in the study using MRI [155], the authors did not assess the whole knee or cartilage volume. Interestingly, in a recent study [157] in which the assessment of knee OA structural changes was performed both radiographically and by quantitative MRI, a change in serum vitamin D level was positively associated with change in cartilage volume. Despite the fact that the mechanisms of the action of vitamin D on cartilage remain unclear, one may speculate that it may have a direct effect on cartilage through vitamin-D-specific receptors.…”

“…Despite the fact that the mechanisms of the action of vitamin D on cartilage remain unclear, one may speculate that it may have a direct effect on cartilage through vitamin-D-specific receptors. Conversely, but not exclusive of the latter, an effect on the subchondral bone metabolism is also possible as the vitamin D levels in serum were also associated with reduced subchondral bone area [157], a known risk factors for knee OA.…”