Vitamin D deficiency and orthostatic hypotension

Vitamin D deficiency is common in older people, especially in northern latitudes where sunlight is scarce in the winter months. It is associated with bone demineralisation, increased fracture risk and increased risk of falls. Vitamin D has also been studied as a possible cause of symptoms related to orthostatic hypotension.¹

Orthostatic hypotension is a common presentation in older patients. It may be secondary to cardiac or neurogenic disease, or associated with a chronic disease such as diabetes or Parkinson’s disease. Orthostatic hypotension can increase the risk of falls and affects quality of life in ageing populations. The combination of vitamin D deficiency in patients with orthostatic hypotension increases the fracture risk.^1,2,3

Case report

We present a case of a 74-year-old woman being investigated for recurrent falls due to syncope. Her symptoms improved once her vitamin D levels were replenished.

The woman initially presented to a primary care centre for recurrent falls. She was generally healthy otherwise, and was a non-smoker and non-drinker. She had a medical history of hypothyroidism, gastritis and diverticular disease. She reported feeling dizzy on getting out of bed in the morning and also feeling lightheaded at times when rising from a sitting position, which settled sometimes after a few seconds before walking. However, she had had more than two non-mechanical falls in the previous six months and was worried that her symptoms were worsening, particularly as she lives alone. 

Her vitals showed a difference of 20mm/Hg in systolic blood pressure checked lying and standing, heart rate 76, respiratory rate 15, SaO2 96% on room air. Basic blood investigations including FBC, renal profile, vitamin B12, folate, ferritin, ESR and thyroid function tests were in normal range, however vitamin D level was 14mmol/L, which is well below the normal reference range.⁴ She was referred to a cardiologist for further investigations and prescribed high dose vitamin D (cholecalciferol-D3).

She was referred for Holter monitor, echo-cardiogram, tilt-table test and CT brain, and was followed up in the clinic at three months and then six months. Her tilt-table test performed was reported negative with advice to continue vitamin D supplementation.

She was also referred to community physiotherapy for assessment of her mobility and safety awareness.

She reported a reduced frequency of symptoms at her six-months check-up and no further falls in the previous three months.

Discussion

Vitamin D deficiency has potential to affect blood pressure regulation mechanisms as well as intravascular volume. We postulated that vitamin D deficiency could play an aetiological role in orthostatic hypertension.^1,2,5

Orthostatic haemodynamic response seems to be impaired in the ageing population^2,6 and is attributed to increasing frailty. Hence, the association of vitamin D deficiency with orthostatic dysfunction makes this a contributory factor as well.^7,8

It has been shown that vitamin D deficiency is prevalent in the older population and addressing this deficiency with supplementation is very cost effective in treating non-musculoskeletal conditions, such as orthostatic hypotension.^1,2

No large scale study has been done to date to evaluate the association of vitamin D deficiency with orthostatic hypotension in older people. However, several studies in the literature show a correlation of vitamin D deficiency with autonomic dysregulation, which is the most important factor in play in orthostatic hypotension.^5,9,10

One hypothesis suggests that the cause of orthostatic hypotension in older people is decreased sensitivity of baroreceptors in the aorta and carotid artery.¹¹ There is an age-related increase in the stiffness of arteries as well as vascular calcification. It is also noted that an increase in thickness of carotid intima-media¹² and vascular calcification was more prevalent in populations with 25(OH)vitamin D deficiency.^13,14

Another study demonstrated that replacement of vitamin D in people with low levels of 25(OH) vitamin D resulted in constant regression in flow wave velocity in people who initially had increased stiffness of carotid, femoral as well as brachial arteries.^13,14

Several in vitro and zoological studies have shown that vitamin D is reno-protective and vasculo-protective.^9,15

Vitamin D has an effect on blood pressure through different mechanisms, including suppression of the renin angiotensin aldosterone system (RAAS) via direct activity on vascular cells and suppression of secondary hyperparathyroidism by regulating calcium metabolism.^16,17

It has also been reported that vitamin D deficiency may cause an increase in mean systolic as well as diastolic blood pressure.^10,18,19 Vitamin D deficiency has also resulted in decreased urinary sodium excretion by increasing renin-angiotensin activity. All these findings regressed following vitamin D replacement.^16,17

Therefore, in summary the role of vitamin D replacement in the older population can be said to: 

• Maintain the endothelial functional integrity^{9,11,15,20,21}
• Decrease peripheral vascular resistance 
• Decrease endothelial adhesion molecules 
• Increase nitric oxide 
• Modulate inflammatory cytokines at the vascular bed 
• Decrease platelet aggregation and oxidative stress.

It is also worth mentioning here that some studies have argued against any impact of vitamin D on orthostatic hypotension.^22,23 This emphasises the need for further studies to explore the role of vitamin D in the older population with regards to all risk factors of frailty, including orthostatic hypotension.

Conclusion 

As well as providing a known protective role in preventing bone demineralisation in the ageing population, vitamin D supplementation may also have a protective role in cardiovascular function. Routing vitamin D supplementation in older patients may therefore have a dual benefit of enhanced quality of life through improving or reducing symptomatic orthostatic hypotension, as well as reducing associated falls-fracture risk in the older population. 

References

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