Serum Thyroid Function, Mortality and Disability in Advanced Old Age: The Newcastle 85+ Study

Abstract

Context:Perturbations in thyroid function are common in older individuals but their significance in the very old is not fully understood.Objective:This study sought to determine whether thyroid hormone status and variation of thyroid hormones within the reference range correlated with mortality and disability in a cohort of 85-year-olds.Design:A cohort of 85-year-old individuals were assessed in their own homes (community or institutional care) for health status and thyroid function, and followed for mortality and disability for up to 9 years.Setting and Participants:Six hundred and forty-three 85-year-olds registered with participating general practices in Newcastle and North Tyneside, United Kingdom.Main Outcomes:All-cause mortality, cardiovascular mortality, and disability according to thyroid disease status and baseline thyroid hormone parameters (serum TSH, FT4, FT3, and rT3). Models were adjusted for age, sex, education, body mass index, smoking, and disease count.Results:After adjustment for age and sex, all-cause mortality was associated with baseline serum rT3 and FT3 (both P < .001), but not FT4 or TSH. After additional adjustment for potential confounders, only rT3 remained significantly associated with mortality (P = .001). Baseline serum TSH and rT3 predicted future disability trajectories in men and women, respectively.Conclusions:Our study is reassuring that individuals age 85 y with both subclinical hypothyroidism and subclinical hyperthyroidism do not have a significantly worse survival over 9 years than their euthyroid peers. However, thyroid function tests did predict disability, with higher serum TSH levels predicting better outcomes. These data strengthen the argument for routine use of age-specific thyroid function reference ranges.

Physical Performance in Elderly Outpatients with Subclinical Hypothyroidism Compared with Euthyroid Counterparts

“…Pearce et al [22] reported in their nonagenarians' a mean FT4 of 15.2 pmol/L which is similar to our control group (men and women pooled) of 15.72 ± 2.8 pmol/L (t=0.88, p>0.1); but our SH group was significantly lower (14.02 ± 1.2 pmol/L, t=-3.5, p<0.002). This finding of a lower FT4 in elderly with SH was in agreement with Cardenas et al [3] in the same region, which was formerly goitrous, although this has currently remitted with iodinated salt.…”

“…Studies in highly functional nonagenarians in developed countries suggest a favorable outcome in those with mild TSH elevations [21][22][23]; but in our region the nonagenarian population is small and requires support. Pearce et al [22] reported in their nonagenarians' a mean FT4 of 15.2 pmol/L which is similar to our control group (men and women pooled) of 15.72 ± 2.8 pmol/L (t=0.88, p>0.1); but our SH group was significantly lower (14.02 ± 1.2 pmol/L, t=-3.5, p<0.002).…”

The physiology of endocrine systems with ageing

“…15 However, a subsequent study showed that individuals aged 85 years with subclinical hyperthyroidism did not have a significantly worse 9-year survival than their euthyroid peers. 16 Further, subclinical hyperthyroidism is associated with an increased risk of atrial fibrillation, 17 hip and other fractures, 18 and dementia, 19 particularly among people with TSH concentrations that are lower than 0·10 mIU/L, and those with endogenous thyroid disease. In contrast, older individuals with subclinical hypothyroidism or higher TSH concentrations within the normal range have a lower mortality than do euthyroid individuals or people with lower TSH concentrations.…”

“…26,27 Among older populations, lower FT 4 concentrations were associated with higher physical function, 11,28 whereas lower TSH concentrations predict future disability. 16 This potential adaptive mechanism could also be a hereditary phenotype that contributes to longevity, since the nonagenarian offspring of centenarians were shown to have higher circulating TSH and lower thyroid hormone concentrations than did the offspring of parents who died at younger ages. 29 …”

Thyroid‐stimulating hormone and risk of sudden cardiac death, total mortality and cardiovascular morbidity

“…There has been a long‐simmering controversy about whether an excess cardiovascular risk related to even mild thyroid dysfunction exists, and whether that putative risk could be ameliorated with thyroid medication. Previous cohort studies and meta‐analyses on thyroid dysfunction and cardiovascular outcomes have provided conflicting results. Furthermore, there has been paucity of published data on the association of thyroid function and sudden cardiac death (SCD).…”