Date of Award

2014

Document type

Thesis

Degree Name

MD (Medical Doctor)

First Supervisor

Professor David Williams

Funder/Sponsor

Department of Geriatric and Stroke Medicine, Beaumont Hospital, Dublin.

Keywords

Bone, Cardiovascular Health, Older People, Vitamin D Deficiency, Osterporosis

Abstract

It is increasingly recognised that vitamin D deficiency is highly prevalent in Ireland and worldwide particularly at higher latitudes. In addition to its well established role in bone health, initial animal studies have established a relationship between vitamin D deficiency and cardiovascular dysfunction including cardiac hypertrophy, fibrotic change and elevated blood pressure .Emerging evidence notes that age associated arterial stiffness is accelerated in the presence of cardiovascular disease and arterial ageing is a risk factor for adverse CV outcomes. PWV is currently accepted as the most simple, non- invasive, validated, robust and reproducible method to determine arterial stiffness.

Osteoporosis is highly prevalent both in Ireland and worldwide and represents a significant economic burden Despite the high burden of osteoporosis in nursing homes, several studies have suggested that osteoporosis screening and therapies are underutilized in the nursing home population. Despite the accumulating evidence of efficacy, recent international studies of osteoporosis management in this setting indicated that intervention rates remain low, which raises concerns about underdiagnosis, and undertreatment of this disease.

In this thesis I sought to

-determine the prevalence of vitamin D deficiency among a screened population of community dwelling elderly patients.

-determine the repeatability of PWV measurement in a hospital setting in a cohort of older patients using the Vicorder apparatus.

-determine whether vitamin D replacement leads to changes in arterial stiffness in vitamin D deficient patients.

-compare the efficacy of two different doses of intramuscular vitamin D in providing supplementation and whether there is a difference in their effect on arterial stiffness.

-determine whether the medical management of osteoporosis in a nursing home population is different between a geriatric led and general practitioner led service and to assess the appropriateness of the medications prescribed.

I found that 61% of community dwelling elderly people in North Dublin were deficient in vitamin D. Physicians should have a low threshold when considering treatment of suspected vitamin D deficiency in the older population, given the high prevalence found in this and other studies. A vitamin D rich diet, exposure to sunlight along with oral supplementation should be recommended.

In the Vicorder repeatability study, I found high levels of both within- and between observer repeatability, with values of intraclass correlation coefficients ranging from 0.8 - 0.93. Results showed that the highest repeatability was achieved using the traditional arterial path length (0.93) when compared with the adapted arterial path length (0.88). I conclude that this non-invasive method of assessing arterial stiffness has the potential to be included in the clinical assessment of older ambulant patients.

Previous studies have demonstrated that vitamin D deficiency may lead to impairment of vascular effects leading to abnormalities in central arterial stiffness. I noted a significant improvement in Augmentation Index (Alx) from week 0 to week 8, with a mean difference of 3.803+/-1.76 seen in the group who received the higher vitamin D dose (p=0.033). In the group that received 100,000IU vitamin D, median PWV decreased from 12.2(5.1-40.3) m/s to 11.5(4.3-14.9) m/s over the eight week study period (p=0.22). Further research is needed to investigate whether sufficient supplementation of vitamin D by a reliable method could result in positive functional changes in arterial stiffness. I was unable to find any correlation between PWV and hsCRP, MMP-9 or OPG as had been demonstrated in a number of previous studies. This may be due to our small sample size.

Low increases in vitamin D status followed the administration of 100,000111 and 50,000IU doses of cholecalciferol indicating that intramuscular use of these doses of vitamin D may not be adequate to achieve optimal vitamin D levels. Ultimately, the question of whether vitamin D supplementation improves vascular health can only be determined by performing large randomised controlled trials, specifically designed to answer this question. Until appropriate trial data are available, extending the prescribing indications for vitamin D beyond its current use in osteoporosis cannot be justified.

I calculated FRAX scores on patients recruited, a score which estimates the 10-year probability of hip fracture and major osteoporotic fractures. Results showed that when prescribing patterns for geriatric led NH residents were examined, only 33% of subjects with high FRAX scores were on calcium and vitamin D and only 11 % were on bisphosphonate therapy. In a similar analysis in GP led NH residents, only 34% of those with high FRAX scores were on calcium and vitamin D with a further 14% on bisphosphonate therapy. In general, our findings demonstrated a high fracture risk as determined by FRAX score in both types of facilities. This was coupled with a low level of use of anti-resorptive therapy and almost negligible DEXA scanning. There appeared to be no difference in prescribing patterns between the two types of nursing homes. Current guidelines for treating this subpopulation of older, often poorly mobile or bedbound elderly are unclear and further longitudinal research is needed to develop guidelines to aid the management of osteoporosis in the long-term care setting.

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Comments

A thesis submitted for the degree of Doctor of Medicine from the Royal College of Surgeons in Ireland in 2014.

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