Live Long & Prosper 🖖

* I have written this blog piece with everybody in mind. I want people from the general public and also other physiotherapists/health care professionals to be able to get something out of this blog.

** These studies all demonstrate correlations between factors, not causation. This means there is an association; it does not mean that one factor causes another.

Every year people will have blood tests, their blood pressure taken and potentially asked a couple of questions about their diet and lifestyle. But are these the best tests to demonstrate someone’s health? Should we be using other tests that help predict mortality and how functional we are going to be in the future?

Here are some factors that are strong predictors of mortality and functional capability. There are others, such as walking speed/distance, foot speed and sleep which I may go on to talk about at a later date.

1. Cardiorespiratory Fitness/VO2 Max.

Cardiorespiratory Fitness (CRF) is a good risk predictor of all-cause mortality as it involves the integration of multiple systems, if one is not working particular well it will directly affect overall CRF. CRF is measured as VO2 Max – this is the maximum amount of oxygen an individual can use during intense exercise (1). Both measured and predicted CRF strongly predict health outcomes (2).

CRF is determined by genetic and non-genetic factors. Now obviously we aren’t able to change the genetic factors, but training and changes in lifestyle can affect your CRF.

VO2 max decreases by 10% and 7% in men and women respectively per decade from the age of 25 (3). This drop off is inevitable, and men actually see a higher rate of drop off than women as they age. However, if you take an endurance trained 70-year-old, they can exhibit the same biological age as an untrained 50-year-old based on VO2 max (3).

That same endurance trained 70-year-old will also demonstrate a 3.5-fold higher VO2 max compared to their untrained peers (4). This higher VO2 max is associated with a larger functional reserve above the frailty threshold and is also associated with a lower risk of disability/mortality.

VO2 max is measured in ml/kg/min. An average VO2 max is 42 and 36ml/kg/min for a healthy untrained male and female respectively (3). It is considered that you need a VO2 max of 17.5ml/kg/min to enjoy an independent lifestyle.

A 2005 study concluded, after looking at data from 41 trials including 2102 participants, that a healthy but sedentary 67-year-old who exercised aerobically for 30-35 minutes, 3 times per week, after 16-20 weeks of training would expect 3.8ml/kg/min increase in their VO2 max (5). Just a 1ml/kg/min higher VO2 max was associated with a 9% reduction in all-cause mortality after an 11 year follow up (6).

So effectively if you did roughly ¼ of the exercise programme you would be reducing your risk of death by 9% within the next 11 years.

2. Muscle Strength

As we age, both our muscle mass and strength decreases, a process called sarcopenia (7). Skeletal muscle decreases by 3-10% per decade after the age of 25 (4). This decrease in muscle mass and strength contributes to the development of functional limitations and disability in old age (8).

Again, muscle strength has been shown to be another good predictor of all-cause mortality. In particular, hand grip strength and knee extensor strength, as both have shown to be important predictors of function in adults in a variety of settings (9) and all-cause mortality (10).

During a recent systematic review of 38 studies which included approximately 2 million participants. The authors found those with higher muscular strength measured by hand grip strength had a 31% reduced all-cause mortality rate and those with higher knee extension strength levels had a 14% reduced all-cause mortality rate when compared to adults with lower hand grip and knee extension strength respectively (11).

So why is handgrip and knee extensor strength such a good predictor of all-cause mortality?

Handgrip strength has been proposed to reflect overall strength status of the elderly (12). Effectively it is presumed that if you have a strong grip at an older age you are more likely to be physically active and therefore be overall stronger than someone who has a weaker grip. It is a quick, easy and reliable test that someone can do to get a small insight into how someone functions overall. Grip strength has also been used to predict length of stay on admittance to hospital (13).

Knee Extensor strength again is a relatively good predictor of lower limb strength. Your knee extensors are used during a variety of functional tasks such as, walking, sit-to-stand, stair climbing and to prevent falls (9). Although most studies use isometric strength testing, I prefer to test this in a more functional way; how many sit-to-stands can you do in 30 secs for example. This also gives me an insight into how the person moves as well as their global lower limb strength.

Muscle strength is so important that the World Health Organisation and the American College of Sports Medicine, amongst other organisations, recommend a minimum of 2 strengthening sessions on non-consecutive days per week to not only improve fitness, but to reduce the risk of mortality (14).

It seems that habitual daily activity is insufficient to maintain muscle strength and mass. However, there has been 30%-170% strength gains in the elderly population (seen even in those over 90!) after a 6-8 weeks training programme consisting of 1-3 sessions per week (7).

3. Sit to Rise Test (SRT)

Some people may have heard of this test as it was on a BBC TV show “How to Stay Young”. This is a simple test that assesses the ability to sit and rise from the floor. It quantifies the number of supports needed to move from the floor to standing (hand, knee, elbow etc.) and whether there is a partial loss of balance/stability whilst completing the test.

The inability to complete this test is closely related to a risk of falling, but if someone has fallen it is of great importance people are able to return an upright position (15).

This test was proposed in the late 1990s (16); you start with a score of 5 for sitting and rising separately, so a maximum score of 10. One point is subtracted for each use of a support (hand, knee, elbow etc.) on completing the task. A further 0.5 point is subtracted if there is a partial loss of balance.

A 2012 study tested 2002 adults between the age of 51-80 who performed the SRT; there was a median follow up time of 6.3 years.

The men and women who scored in the lowest score range (0-3) were associated with a 6-fold higher all-cause mortality risk whereas those who scored in the highest score range (8-10) were associated with a particularly low risk of death during the tracking period.

It was found that just a 1 point improvement in the SRT was associated with a 21% reduction in mortality. There are some limitations to the study, however it is a good rough indicator of how well your body is functioning (17).

So, what does this all mean?

Well if you:

1. Have a higher cardiorespiratory fitness,

2. Have increased muscle strength, especially hand grip and knee extensor strength,

3. Have the ability to sit and rise from the floor without support or losing balance,

Your risk of mortality will be reduced and you will more likely continue to be independent in later life.

If you don’t, don’t worry as there are many changes to your lifestyle and a variety of different exercises/activities you can do to help.

References:

1.Fujiyoshi, A. 2018. Cardiorespiratory fitness, a promising modality for treatment and risk prediction. European Journal of Preventive Cardiology; 25(3) 306-308.

2. Ross, R. et al. 2016. Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign: a scientific statement from the American Heart Association. Circulation; 134 e653-699.

3. Strasser, B. and Burtscher, M. 2018. Survival of the fittest: VO2max, a key predictor of longevity? Frontiers in Bioscience; 23(23), 1505-1516.

4. Burtscher, M. et al. 2008. Superior endurance performance in aging mountain runners. Gerontology; 54(5), 268-271.

5. Huang, G. et al. 2005. Controlled Endurance Exercise Training and VO2 max Changes in Older Adults: A Meta-Analysis. Preventive Cardiology, 8: 217-225.

6. Laukkanen, J.A. et al. 2016. Long-term change in cardiorespiratory fitness and all-cause mortality: a population-based follow-up study. Mayo Clinic Proc; 91(9), 1183-1188.

7. Bautmans, I. et al. 2014. Sarcopenia and functional decline: Pathophysiology, Prevention and Therapy. Acta Clinica Belgica; 64:4, 303-316.

8. Volaklis, K. et al. 2015. Muscular strength as a strong predictor of mortality: A narrative review. European Journal of Internal Medicine; 26, 303-310.

9. Martien, S. et al. 2015. Is knee extension strength a better predictor of functional performance than handgrip strength among older adults in three different settings? Archives of Gerontology and Geriatrics; 60(2), 252-258.

10. Legrand, D. et al. 2014. Muscle Strength and physical performance as predictors of mortality, hospitalisation, and disability in the oldest old. Journal of the American Geriatrics Society; 62(6), 1030-1038.

11. García-Hermaso, A. et al. 2018. Muscular Strength as a predictor of all-cause mortality in apparently healthy population: a systematic review and meta-analysis of data from approximately 2 million men and women. Archives of Physical Medicine and Rehabilitation.

12. Visser, M. et al. 2000. Skeletal muscle mass and muscle strength in relation to lower-extremity performance in older men and women. Journal of American Geriatrics Society. 48, 381-386.

13. Kerr, A. et al. 2006. Does admission grip strength predict length of stay in hospitalised older patients? Age and Ageing; 35(1), 82-84.

14. World Health Organisation. 2011. Physical Activity in Adults. http://www.who.int/dietphysicalactivity/factsheet_adults/en/

15. Alexander, N.B. et al. 1997. Rising from the floor in older adults. Journal of American Geriatric Society. 45:353-359.

16. Araújo, C.G.S. 1999. Teste de sentar-levantar: apresentação de um procedimento para avaliação em Medicina do Exercício e do Esporte. Rev Bras Med Esporta; 5, 179-182.

17. Brito, L.B. et al. 2012. Ability to sit and rise from the floor as a predictor of all-cause mortality. European Journal of Preventive Cardiology.