Vitamin D status and physical function in older Finnish people: A one-year follow-up study

Highlights

• Fifth of aged people living in Southwest Finland had 25OHD deficiency (<50 nmol/l).

• 25OHD deficiency predicted deterioration in physical function (PF).

• 25OHD concentration should be ≥75 nmol/l in order to prevent deterioration in PF.

Abstract

Objective

The aim was to describe vitamin D status and its association with changes in PF during 12 months in Finnish community-dwelling elderly (≥65 years).

Methods and results

Baseline serum 25-hydroxyvitamin D (25OHD) concentration was measured by enzymeimmunoassay, and participants (n = 518) were divided according to 25OHD to three groups (I <50 nmol/l, II 50–74.9 nmol/l, and III ≥75 nmol/l). PF (maximal isometric extension strength of right and left knee, and time in five-repetition sit-to-stand test (5STS) and 10-m walking test) was measured at baseline and after 12 months. 25OHD deficiency (<50 nmol/l) was found in 20.5% of the participants. During a 12-month follow-up, differences in changes in knee extensor strength of right (p = 0.044) and left (p = 0.010) lower extremity and in 10-m walking test (p = .040) between the groups were significant. According to further pairwise comparisons these differences were between groups I and III (right knee, p = 0.036; left knee, p = 0.009; 10-m walk, p = 0.044), with the exception of left knee extensor strength in which there were also significant difference between groups I and II (p = 0.039). All significant differences in changes were in favour of group II or III. Significant differences in changes in knee extensor strengths maintained after adjustments for group (intervention/control), parathyroid hormone, and baseline level of knee extensor strength.

Conclusions

Prospective analyses showed low 25OHD concentrations (<50 nmol/l) to be associated with deterioration in PF during 12 months compared with high 25OHD concentrations (≥75 nmol/l).

Introduction

Vitamin D deficiency is a public health problem worldwide (Mithal et al., 2009). Approximately 50–70% of community-dwelling older people in Europe have vitamin D deficiency, as defined by serum 25-hydroxyvitamin D (25OHD) of less than 50 nmol/l (Chan & Woo, 2011). In Finland, vitamin D intake and vitamin D status has been low in all age groups (Lamberg-Allardt, Brustad, Meyer, & Steingrimsdottir, 2013).

There is increasing evidence to show that vitamin D deficiency is an important risk factor for various adverse health outcomes (Holick, 2007, Lamberg-Allardt et al., 2013). Evidence of the role of 25OHD in relation to physical function (PF), and especially in relation to changes in PF, is limited. Although many cross-sectional studies have shown that low 25OHD concentrations are associated with lower physical performance and muscle strength (Dukas, Staehelin, Schacht, & Bischoff, 2005; Gerdhen, Ringsberg, Obrant, & Akesson, 2005; Wicherts et al., 2007; Dam, von Mühlen, & Barrett-Connor, 2009; Shahar, Levi, & Kurtz, 2009; Pramyothin et al., 2009, Dretakis et al., 2010, Houston et al., 2011, Houston et al., 2012, Mastaglia et al., 2011, Michael et al., 2011, Boersma et al., 2012, Menant et al., 2012, Toffanello et al., 2012, Boyé et al., 2013, Gschwind et al., 2014; Janssen, Emmelot-Vonk, Verhaar, & van der Schouw, 2013), others have found no association (Annweiler et al., 2009, Chan et al., 2012, Mathei et al., 2013). The results of few longitudinal studies with 2–4-year follow-ups are inconsistent, some showing low 25OHD levels to be associated with decline in physical performance and muscle strength (Visser, Deeg, & Lips, 2003; Wicherts et al., 2007, Dam et al., 2009, Houston et al., 2011) while others show no association (Verreault et al., 2002, Michael et al., 2011, Chan et al., 2012, Houston et al., 2012).

The objective of this study was to describe the cross-sectional associations between 25OHD and PF and associations between 25OHD and changes in PF during 12 months in Finnish community-dwelling people aged 65 and older.