Osteomalacia

Introduction

The elderly population is at particular risk of vitamin D deficiency and osteomalacia [1]. The two main sources of vitamin D are diet and sunlight exposure, the latter being more important [2]. The mean dietary intake of vitamin D in elderly British people is about one-fifth of the level recommended by the Department of Health [3]. In addition elderly people have less sunlight exposure and less efficient photosynthesis of vitamin D [4, 5]. Further, ageing is associated with a decline in renal function resulting in a decreased activity of 1[Alpha]-hydroxylase. This may also be a factor contributing to osteomalacia in elderly people [6]. Most of the research on vitamin D deficiency in the elderly has been performed in institutionalized individuals and suggests that this group is especially at risk [7, 8]. Community-based studies of elderly people have reported lower levels and diminished seasonal variation of vitamin D levels compared with younger subjects [9, 10]. Clinically this deficiency of vitamin D in elderly people may not only result in osteomalacia but may also be associated with muscle weakness (unpublished data R. H. Hyatt et al.).

The problem of rickets and osteomalacia in British Asians was first reported over 30 years ago by Dunnigan et al. [11]. Since this original report many studies have looked at the problem of vitamin D deficiency and osteomalacia in Asians. Elderly Asians living in Britain are likely to be at an even higher risk from vitamin D deficiency and osteomalacia than younger Asians. However, to date there are few data to confirm or refute this suspicion. The aim of the current study was to try to assess the prevalence of vitamin D deficiency and the risk of osteomalacia in apparently healthy elderly Asians living in the community.

Methods

Local ethical committee approval was obtained prior to approaching any subjects. Healthy, community-living elderly Asians (over 65 years old) were recruited from two sources: general practitioner lists and from a number of Asian day centres run by Birmingham Social Services Department. (In the context of this study 'Asians' implies people with an ethnic origin in the Indian subcontinent and adjacent territories.) Approval was obtained from Birmingham Social Services Department to approach clients in their day centres. Healthy elderly white controls were recruited from a local church day centre, while young Asian and white controls were made up from hospital staff. Written informed consent was obtained from all volunteers.

The study was performed in the last week of March and first week of April when vitamin D levels are likely to be at their lowest. It was not possible to match the sample and elderly control groups for age and sex because of the short time period and difficulties in recruiting elderly Asians. All elderly subjects and controls answered a questionnaire covering ethnic subgroup, religion, personal health (including [TABULAR DATA FOR TABLE I OMITTED] drug history), musculoskeletal symptoms and dietary habits. Heights, weights and demi-span were also measured by one of the authors (T.S.).

Blood samples were obtained for haematology and biochemistry including parathyroid hormone (PTH) and 25-hydroxyvitamin [D.sub.3] (25-OH[D.sub.3]). All samples were placed in an ice pack at 0 [degrees] C for transfer to the laboratory. The samples for PTH and 25-OH[D.sub.3] were centrifuged within 3 hours of collection and stored at -20 [degrees] C. Basic biochemical analysis was performed using a Kodak Ektachem 700 analyser. Intact PTH was assayed using the Nichols Institute Diagnostics kit and 25-OH[D.sub.3] was assayed using a modification of the method of Preece et al. [12].

Forty-one elderly Asians (23 men, 18 women), 20 elderly whites (5 men, 15 women), 24 young Asians (19 men, 5 women) and 21 young whites (6 men, 15 women) were recruited, though some of the data were incomplete in some cases due to insufficient samples for analysis. All data were analysed using SPSS. Groups were compared using the Mann-Whitney and [[Chi].sup.2] tests and analysis of variance (ANOVA).

Results

The mean age of the groups was 72 years (range 67-91) for elderly Asians, 74 years (range 67-83) for elderly whites, 31 years (range 19-63) for young Asians and 30 years (range 20-64) for young whites. The elderly Asians had a lower body mass index (26.7 kg/[m.sup.2] [+ or -] 6.1) than their white counterparts (32.2kg/ [m.sup.2] [+ or -] 4.5, p [less than] 0.001).

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