Associations between the Toe-Brachial Index (TBI) and health-related quality of life in older people

The harmful effects of peripheral artery disease (PAD) differ in their severity due to the progress of the disease itself as well as any additional risk factors like diabetes mellitus and smoking. However, not everyone is equally affected or as susceptible to the disease. There is one group that is more affected than others—the elderly. Advanced age is a non-modifiable risk factor for PAD and there is sufficient evidence that older people have a harder time dealing with the symptoms as well as making the necessary lifestyle modifications as a part of the treatment. There is even evidence of direct association of TBI with health-related quality of life (HRQoL) in the elderly.

In this blog you will learn:

• What are the effects of low Ankle-Brachial Index (ABI) and Toe-Brachial Index (TBI)?
• What is health-related quality of life (HRQoL)?
• Is there an association between Toe-Brachial Index (TBI) and HRQoL?

What are the effects of low Ankle-Brachial Index (ABI) and Toe-Brachial Index (TBI)?

Of the many methods for diagnosing PAD, the Ankle-Brachial Index (ABI) assessment has become the go-to diagnostic method in clinical practice (1, 2, 3, 4, 5, 6). Cost-effective and convenient, its only comparable counterpart is the Toe-Brachial Index (TBI). Nevertheless, the TBI assessment is usually performed only in selected patients in whom the ABI is unusable for diagnosis of PAD, i.e. those with incompressible arteries (7).

Arteries affected by medial arterial calcification are most found in individuals with diabetes, rheumatoid arthritis, and renal insufficiency (8, 9, 10, 11). However, the toe arteries are rarely affected and are a suitable location for measuring blood pressure using miniature cuffs equipped with photoplethysmographic sensors (12). Differences from ABI, with the addition of the lower numerical value of both normal and diagnostic-for-PAD TBI, stop here as there is linear association between the numerical value and severity of PAD and a host of other medical issues.

Low and even borderline ABI is associated with higher rates of stroke and heart failure (HF) and is useful for improving the accuracy of cardiovascular risk prediction beyond the FRS (Framingham Risk Score) (13, 14). Unusually high ABI (generally ≥1.30 or 1.40) is likewise associated with cardiovascular issues, specifically with the risk for myocardial infarction (MI) in at-risk groups but has no other diagnostic value (15). Comparably, low TBI is an informal predictor of mortality in dialysis patients and those with chronic kidney disease (CKD), and is associated with increased risk of diabetic nephropathy and recurrent cardiovascular disease (CVD) (16, 17, 18, 19). Recently, there has also been evidence that low TBI may be associated with HRQoL in elderly individuals.

What is health-related quality of life (HRQoL)?

The term health-related quality of life (HRQoL) indicates a multi-dimensional concept used to examine the impact of health status on quality of life (20). More practically, patients are required to fill out a comprehensive questionnaire with questions pertaining to their physical as well as mental and emotional well-being. One such questionnaire was also used in a study that aimed to investigate the association between TBI and HRQoL in a group of older patients at risk of vascular issues (21).

Is there an association between Toe-Brachial Index (TBI) and HRQoL?

Advanced age is a risk factor for PAD, as are diabetes mellitus and tobacco smoking—all of them were also included in the criteria for inclusion in the above-mentioned study that took place between January 2013 and February 2015 in the Sydney and Newcastle regions in Australia (21, 22, 23, 24). Participants were recruited among the patients of six podiatry clinics and included those over the age of 50 years with a history of diabetes mellitus or smoking and anyone over the age of 65 years (21). In the end, 100 individuals with a mean age of 70 years participated in the study (21).

They received a TBI assessment, filled out the questionnaires and their HRQoL was again assessed four weeks later (21). The results were telling, but inconclusive in some respects. Patients with lower TBI scores had greater and more frequent interference with social activities (21). However, due to the small sample of participants and the even smaller number with painful PAD symptoms (i.e. intermittent claudication), researchers did not find significant correlation between PAD symptoms and social activities (21). They also noted that TBI is indicative of lower extremity vascular health in general and may be affected by other conditions like peripheral neuropathy (21).

Another important finding was that there is a significant relationship between low TBI score and physical activity, which reflects problems with work or other daily activities caused by physical health (21). In other words, individuals with low TBI are more likely to report limitations in the type and amount of work they perform (21). It should be noted that only 28 % of participants had a TBI less than 0.7, indicating possible PAD, but only 5 % of them (of all participants) reported typical symptoms. This led the researchers to hypothesise that the correlations they found may have underestimated the relationship between the TBI and HRQoL, calling for further investigation (21).

There is tentative evidence that low TBI is associated with correspondingly lower health-related quality of life (HRQoL) in older individuals, indicating that TBI may be a useful tool for identifying patients at risk of impaired HRQoL.

Why use the Toe-Brachial Index (TBI) for PAD diagnosis?