The best way is not to calculate it at all.

Lung age is used to help patients understand how low their lung function is and is bases on the FEV1 of the patient. If it is 100% of the reference value the lung age is exactly the same as the actual age. If the FEV1 is lower, the lung age will be higher as the real age of the patient. The new reference equations GLI (= Global Lung Initiative) from Prof Quanjer are valid world, wide, for all ages (3-95 year) and different for different etnicities. The difficulty is that the relation between age and FEV1 is not a simple formula anymore! The exact relations can be found on:

http://www.lungfunction.org/tools/85-equations-and-tools/equations/111-for-it-engineers-and-manufacturers.html

but, as stated above, this is much more difficult to implement than the old "simple" equations. Those old equations give large mistakes for especially older people (>65 year) and for the age catergory between 15 -25 years.

PS: there are no different eqations for smokers and non smokers: if you are a smoker, your FEV1 will decline earlier and faster and you will therefore automatically get a higher lung age but the calculation should be based on the same GLI equations

The original paper from Morris & Temple Preventive Medicine 1985 vol 14 pg 655- 662 compared different methods but the authors suggested that the formula based on FEV1 was superior.

Lung age = (2,87x height in inches) - (31,25 x observed FEV1) - 39,375

But Vito has a valid point….

The hrct study may predict the lung age in my research!

You run the predicted formula backwards to calculate at what age the measured value would be normal. It is supposed to make the result more understandable to the patient but it seems nonsense to me. You could do the same with gender and height but why? I think it is quite understandable to say that the lung function is 30% of what it should be. Patients understand that. It doesn't help to tell someone that they have the lungs of a 120 year-old.

yes ! we may take the PFT, imaging , gallium, even PET/CT into consideration !

Please, look this reference: Morris JF. Spirometry in the evaluation of pulmonary function. West. J. Med. 1976; 125: 110-118.

I think the best academic respone that exactly focus on question belongs to FRANS DE JONGH and imaging does not help any more.

Lun age is not a strong concept as it is based only on basic lung mechanics as we know that patients may have gas exchange alterations and other biological or clinical alterations. Physiological lung ageing has few points in common with COPD lung ageing but the increase in residual volume.

The only positive point would be to say to a smoker that smoke reduced is lung function as if he/she was, say 30 years older. If this is efficient to reduce the smoking habit OK. I am not sure that this is true.

The Morris and Temple lung age (LA) equations (from 1985) are based on data collected over 40 years ago, based on a biased Caucasian sample. These LA equations are generally the ones provided in spirometry instruments. It is meant to estimate the age at which the observed FEV1 would be considered normal, which in smokers is generally greater than their chronological age. This is hoped to be a prompt to encourage smokers to quit their habit, it is not meant to be diagnostic. Even though ATS/ERS recommend that spirometric predictive equations be regularly updated this has not happened with LA equations, and this could be part of the reason why research using LA for smoking cessation has been inconclusive.

Newer LA equations from Australia (Newbury W, Newbury J, Crockett A. Exploring the need to update lung age equations. Prim Care Respir J. 2010;19(3):242-47. DOI: 10.4104/pcrj.2010.00029.) were based on an Australian sample, with data collected in 2007. These provide an updated option; the Australian Lung Foundation provides a Primary Care Respiratory Toolkit, with a Lung Age Estimator, based on the Newbury et al equations, available at

http://doctorwidget.com/alf/ignition/index.php/alf_pcrt#

Further related research (Newbury W, Lorimer M, Crockett A. Newer equations better predict lung age in smokers: a retrospective analysis using a cohort of randomly selected participants. Prim Care Respir J. 2012;21(1):78-84. DOI: 10.4104/pcrj.2011.00094) gives further insight into why lung age equations should be updated.

Bear in mind too that predictive equations that match your population should be used.

We have calculated percentiles for lung function, see boelle et al using the kulich method

this allows a patient to know how they fare against their peers with the same disease

1. Are you a clinician, and thus you need an established formula, or do you look for some new good method?

2. Do you want use only results of spirometry or results of other examinations ?

If (1) you look for a good method (2) using only spirometry, try to examine position of a patient on the plane determined by FVC and FEV1 [see my article in Respir Res].

Please see my publications about the subject ....they are free on researchgate. 

https://www.pftforum.com/blog/estimated-lung-age-ela/

we can use spirometry ( PFT) FVC & FEV1

but is not a concept as it is based only on basic lung mechanics)