A prospective study of the associations between 25‐hydroxyvitamin D, sarcopenia progression and physical activity in older adults

roidism as the cause. Particularly, individuals with ischaemic heart disease are more likely to develop atrial fibrillation. Similarly, any severe intercurrent illness that may lower TSH, for instance pneumonia, may also be complicated by atrial fibrillation. Thus, the major cause of grade I SCH is nonthyroidal illness, and this becomes more prevalent with ageing. The association between atrial fibrillation and grade I SCH, therefore, persists despite multivariate analyses in these epidemiological studies, because although chronological age is controlled for by the analysis, biological age is not taken into account. And, as detailed in our original article, alterations in the thyroid axis with age mean that low TSH is likely to be a surrogate for advanced biological age or even ‘frailty’. We agree with the authors that grade I SCH should not be regarded as a benign condition, as these individuals are clearly at excess vascular risk. However, currently there is no evidence that demonstrates an improvement in outcome by treating such people for thyrotoxicosis. Until such information becomes available, we would recommend physicians to consider treating individuals with grade I SCH with conventional medications for those with vascular risk, such as a statin, aspirin or perhaps a beta-blocker. We would reserve treatment of hyperthyroidism with radioiodine or antithyroid drugs for certain patients with persistent grade II SCH.