CME Slides Forum - L. Cuppari

A joint Congress by ERA-EDTA and ISN

EVALUATION OF PHYSICAL ACTIVITY IN CKD: APPLICABILITY OF SIMPLE TOO

Liliana Cuppari, Sao Paulo, Brazil

Chair: Naomi Clyne, Lund, Sweden

Rolfdieter Krause, Berlin, Germany

cuppari

Dr L. Cuppari
Division of Nephrology
Federal University of Sao Paulo
Sao Paulo, Brazil

Thank you. It’s a pleasure to be here and I would like to thank the organizers for the invitation for this presentation.

In this talk I will briefly present the definition of physical activity and I will also describe the main methods and tools for measuring physical activity. I’ll also show the available data on the level of physical activity in CKD patients and I will also present some results that we have performed some studies on active energy expenditure in hemodialysis patients.

Physical activity is defined as any bodily movement produced by the contraction of skeletal muscle resulting in energy expenditure. This includes not only planned, structured and repeated bodily movements which is actually exercise but also bodily movements performed for daily life activities such as household work, transportation and leisure time activities. Clearly to perform any of these types of physical activities one has to consider having attributes associated with the physical functioning and physical fitness, as very well explained in the previous presentation.

It’s similar to what is observed in the general population. Sedentary behavior is associated with high risk of mortality. In this study with incident hemodialysis patients we can see that those patients classified as sedentary had 62% higher risk of mortality over one year even adjusting for all other factors associated with mortality. Thus to monitor the level of physical activity of these patients is important even when you do some kind of intervention or to improve or to increase physical activity but this is not so easy.

The accurate measurement of physical activity is somewhat difficult. By using different methods a number of parameters can be measured. They include physical activity scores, number of steps, the results of an accelerometer and the derived ones such as metabolic equivalents and active energy expenditure.

These methods can be objective, most of them measure body movements, or subjective by using physical activity questionnaires.

Among the objective measures pedometers are devices that measure the number of steps taken and these kind of devices have the advantages of being of low cost, easy to use and they can be a good tool of intervention and also for stimulating individuals, or patients to increase physical activity since the subject can see the readings at any time. But it has some important limitations because it’s not possible, with this device, to measure upper body activity or load and it’s not sensitive to the intensity of physical activity.

Accelerometers are more sophisticated devices that measure physical activity because it measures the physical movement in up 3 dimensions and because of this they measure more complex activities, upper body movements and it’s more sensitive which is good for patients who do light activities. But it also has some limitations. Because of this high sensitivity it can measure any type of vibration even those not related to body movements. It’s also shown that it can underestimate strength movements.

Subjective measures: physical activity questionnaires are most used in large studies and the main advantage is the low cost and it is very practical to administer. However, the main limitation of questionnaires is the low accuracy mainly related to reporting errors or to individual variations in weight, intensity of physical activity, metabolic factors and disease.

As far as I’m concerned, there is no specific questionnaire developed for CKD patients but in this study by Doctor Johansen and co-workers, they tested these 3 questionnaires designed for the general population in 39 patients on hemodialysis and they used as a reference a 3 axis accelerometer. The main findings of this study are that this human activity profile questionnaire was the best correlated with physical activity explaining 61% of the variation of physical activity.
Although lower results of the other questionnaires, they are considered good since this is the number found in other studies in validation studies in other populations. Thus these authors concluded that these questionnaires are valid to be used in the hemodialysis patients.

There are a few studies that evaluated the level of physical activity of CKD patients. By using a pedometer this study showed that hemodialysis patients were 51% less active than healthy controls. In this other study by using an accelerometer a similar result was found. Hemodialysis patients were 35% less active even when compared with sedentary healthy subjects.

In this other work it was demonstrated that in the dialysis day patients were 24% less active compared with non-dialysis day. The authors attributed this finding to the fact that the patients stay seated for 4 hours during the dialysis session.

More recently a new device has been developed; devices that combine sensors of movement with those associated with physiological response of physical activity such as heat flux, skin temperature and near body temperature and galvanic skin response. By processing these parameters through algorithms and appropriate formulas it’s possible to estimate parameters of energy expenditure such as metabolic equivalent, total energy expenditure and active energy expenditure.

As you know, double labeled water is the gold standard method for measuring total energy expenditure in free living conditions. Thus, by using this it’s possible to estimate active energy expenditure from the subtraction of total energy expenditure from the sum of resting energy expenditure and thermic effect of food which is generally 10%.

By using this approach in these studies the authors tested this portable arm band device in comparison with double labeled water to estimate active energy expenditure in 45 free-living subjects. What they found was that the arm band underestimated active energy expenditure in 225 Kcal. They also found a moderate degree of correlation between these two methods.

However, we have to consider that even using double labeled water active energy expenditure was a derived value. Thus it’s possible that adding and subtracting components of the reference method may have some imprecision in these methods. Anyway this method can be useful for evaluating energy expended for physical activity in CKD patients. An issue that has to be evaluated, there are no studies evaluating --. In the last years we have had a series of studies evaluating resting energy expenditure which is the greatest determinant of total energy expenditure. However, physical activity is also an important component of total energy expenditure and it’s quite variable. It’s estimated that for an individual with light to moderate physical activity it’s between 15-30% of total energy expenditure.

Thus, we have ongoing studies on the evaluation of energy expended for physical activity in CKD patients.
In this study we used this portable armband device to estimate active energy expenditure in 22 hemodialysis patients compared with 22 pair-matched, age and gender matched sedentary healthy subjects. The subjects used this portable armband for 5 complete days and two dialysis days were included in the whole period of time.

Here I’m showing you the main characteristics of these patients and as you can see, these patients were relatively young, they were well-nourished, only two patients were diabetic and the haemoglobin level was within the recommended range for hemodialysis patients. Despite this good clinical condition what we found was that even in dialysis day and in non-dialysis day the active energy expenditure was significantly lower than that of healthy sedentary subjects.

The contribution of energy expenditure to total energy expenditure was 15% in patients compared with 24% in healthy subjects.

With this device it’s also possible to evaluate during a period of 24 hours many parameters of physical activity. Here just for example the metabolic equivalent it’s clear that during the dialysis session it’s lower but it’s important to see that even in the non-dialysis day the metabolic equivalent or the energy expended was lower than that of healthy subjects.

When we tested the variables associated with active energy expenditure in a larger sample of hemodialysis patients, we could find in both models a correlation coefficient of 0.30. The meaning is that 30% of the variation of active energy expenditure was associated inversely with age and directly with parameters of muscle mass, such as lean body mass measured by DEXA and body cell mass.

In an ongoing study it’s a multi-centre study we’re using this armband device in hemodialysis patients from Brazil, France, Sweden and Switzerland.

We found similar results comparing dialysis and non-dialysis day. If you look at the distribution of the contribution of active energy expenditure to total energy expenditure, there is a wide variation in these measurements with a median of 14%.

Finally, it’s clear that it’s difficult to evaluate physical activity and these difficulties are associated mainly with differences in the sensitivity of the tools and the greater inter and intra-individual variability. But these simple tools can be useful not only for determining the level of physical activity but also for monitoring physical activity interventions and to more adequately prescribe the energy intake.