Peripheral Arterial Disease (PAD) might not hit the headlines like the measles epidemic or cancer, or be mentioned in the same breath as other more prominent Cardio-vascular Diseases (CVDs) such as Coronary Artery Disease (CAD) and strokes, but is nevertheless a significant predictor of overall cardiovascular health. Unfortunately, many patients with PAD go undiagnosed.
It is estimated that there were at least 202 million individuals with PAD worldwide in 2010 – today that number is likely to be higher due to a variety of reasons . Many remain undiagnosed, even if they are in a risk group for PAD, like smokers, who are also at significant risk of other CVDs, and diabetics (PAD is 3.5 times more common in male and 8.6 times more common in female diabetic patients than in non-diabetics) [2, 3].
Ankle-brachial (Pressure) Index (ABI) measurements can improve the accuracy of cardiovascular risk prediction beyond the FRS (Framingham Risk Score).
The latter are especially at risk since symptoms of PAD can be mistaken for those of (Diabetic) Peripheral Neuropathy (DPN) and, if additional diagnostic tests are not performed, this can lead to misdiagnosis and a delay of proper treatment. It should be noted that there is a strong correlation between PAD and DPN: those diabetics with DPN are two times more likely to also have PAD .
Likewise there is a strong association between PAD and a host of other medical conditions, particularly CVD – Ankle-brachial (Pressure) Index (ABI) measurements can improve the accuracy of cardiovascular risk prediction beyond the FRS (Framingham Risk Score) . Despite this fact and well-researched pathophysiology and risk factors, overall awareness of importance/negative effects of PAD is (from a global perspective) still low, notably amongst the general population which should be the main target of awareness campaigns.
The Growing Number of People with Peripheral Arterial Disease (PAD)
The asymptomatic nature of a significant number of PAD cases (about 40 % patients have no symptoms) makes diagnosis the disease in a timely manner a tall order without appropriate diagnostic tools [6, 7]. These diagnostic tools range from patient-invasive, such as angiography, to patient-friendly, such as ABI and TBI (Toe-brachial Index) measurements – their cost-effectiveness is on the same spectrum – making ABI (TBI) measurement the best tool for large-scale screening of potential patients. Oscillometric ABI measuring devices are particularly well suited for this purpose . But, given the large number of (as yet undiagnosed) patients, they are in short supply, most often there where they would be most needed.
It is estimated that there were about 8.5 million individuals with PAD in the United States in 2000 alone – today that number is likely far higher given the growing global prevalence of PAD . The overall prevalence number (using newer data sets for the period between 2003 and 2012) is estimated at 11.8 % . Research has also shown significant discrepancies between the largest racial groups, indicating that black people are at greater risk of PAD than white people . More broadly speaking, it was estimated that nearly 48.0 % of individuals over 20 years of age had some type of CVD in 2016 .
This situation is not much better on the South American continent, or more specifically Brazil. Though there were few comprehensive studies about the prevalence of PAD, the number frequently cited is 10.5 % . Overall, CVDs are a significant socio-economic burden that accounted for about 31 % of all deaths in 2011 .
The Western-style (unhealthy) diet can also be found across the Atlantic, in Europe, along with a host of other PAD risk factors. It should therefore come as no surprise that in the UK, (asymptomatic PAD) prevalence is at least 8.0 %, but it should be highlighted that this number is from a study conducted in 1991 . In general, about 7.4 million individuals (as of 2019) have some type of CVD .
Germany is nearly equally affected and it is estimated that 3 to 10 % of population has PAD . Germany also has very high rates of CVD-related mortality (where it is the leading cause of overall mortality): 43.9 % of deaths in females and 36.1 % in males in the year 2012 .
France has comparable prevalence of PAD, estimated at 11 %, but it should be noted, as with the UK case, this data is outdated since the study was conducted back in 2000 . A more recent study conducted in 2006 on high-risk patients published far higher numbers – prevalence in excess of 27 % (with the disease diagnosed using an ABI measurement) . In contrast with many other countries, CVDs are not the leading cause of mortality in France: in 2013 CVDs accounted for 25.1 % of all deaths and were second to cancer with 27.6 % .
Spain similarly has a lower prevalence of CVDs; PAD prevalence estimates range between 3.7 and 7.6 % [22, 23, 24, 25]. The prevalence of all CVDs was 5.7 % for males and 4.5 % for females in 2015 .
In comparison with Spain, Italy has a fairly large prevalence of PAD, reported to be 12 % in males and 15 % in females . Mortality from CVDs is also significant: 35 % for males and 43 % for females .
Neighbouring Slovenia is also not (relatively) PAD-free as it is estimated that more than 16 % of individuals over the age of 55 years have the disease . The biggest killers are once again CVDs, accounting for 32 % of all deaths for males and 47 % for females .
The prevalence rates of PAD are even higher in Sweden as it is estimated that roughly 18 % of the population has PAD or any of its symptoms/complications (intermittent claudication/severe limb ischaemia) . Mortality due to CVDs is likewise high: 35 % of deaths in 2016 were attributed to CVDs with cancer coming second .
This situation, from perspectives of both morbidity and mortality, is even worse in Russia. Statistics for PAD are highly ambiguous as (so far) there have not been any large-scale epidemiological studies and there are only (too low) estimates in the 1.5-5 % range, despite the fact that these have been acknowledged as probably false even by the researchers that postulated them . There is no uncertainty when it comes to CVDs in general as Russia still has one of the highest rates of CVD-related mortality in Europe: 53 % of all deaths in 2012 were due to CVDs .
Even worse affected are underdeveloped and developing countries in Africa, especially sub-Saharan countries. Prevalence rates for PAD vary from 3.1 to 24 % for adults aged 50 years and older, who also receive very little treatment . Sub-Saharan Africa is also the only region in the world where the rates of CVD-related deaths increased in the period between 1990 and 2013: 11.3 % of all deaths in Africa in 2013 were due to CVDs .
A wide-range of estimates for PAD prevalence have similarly been postulated in India in absence of large-scale studies that would use more accurate diagnostic methods (ABI measurements instead of the presence of intermittent claudication or other symptoms), in spite of high prevalence of risk factors for PAD. Prevalence is of course particularly high in the elderly (advanced age is a risk factor), with one study (carried out in the State of Kerala) citing the number of 26.7 % for those in the 60-79 years of age group . Other studies estimate that there are at least 41 to 54 million individuals with PAD in India . CVDs in general are the leading cause of mortality in India, responsible for about a quarter of all deaths – 80 % of them due to CAD .
Australia, on the other hand, has PAD prevalence rates comparable with other Western countries, i.e. in the area of 15 % . However, it should be noted that not all inhabitants are affected equally. Indigenous Australians are at a 3-times greater risk of developing PAD than non-Indigenous Australians and at a 5-times greater risk for any cardiovascular event (due to the significantly higher prevalence of risk factors) . Speaking of which, CVD prevalence was 22 % amongst Australians between 2014 and 2015 and nearly one third of all deaths were CVD-related .
Overall, PAD prevalence rates of are projected to rise in most countries due to an increase in the number of patients with diabetes, smokers and a generally ageing population.
The prevalence of diabetes is rising in both developed, Western countries, such as the United States and UK, particularly among young adults and children, and developing, low and middle-income countries [43, 44, 45]. Developing countries also have it worst when it comes to smoking rates since they are home to the majority of all smokers worldwide and it is projected that their number will likely go up in the future . Still, even with sound prevention programmes in place, excellent healthcare systems and notable awareness about PAD, some developed countries are struggling with its rising prevalence. Germany, for example, is battling with the increasing socio-economic burden connected with Critical Limb Ischaemia (CLI), an advanced stage of PAD which often ends in amputation .
The growing prevalence of PAD, particularly in developing nations, will require greater investment in raising awareness about the disease, in both the general population and clinicians, and the propagation of diagnostic tools for large-scale screening on the basis of an ABI measurement.