The influence of age on the relationship between subclinical hypothyroidism and ischemic heart disease: a metaanalysis.
BACKGROUND
Subclinical hypothyroidism (SCH) is a common condition that has been associated with ischemic heart disease (IHD) in some, but not all, studies. This may be due to differences in study design and the characteristics of participants.


OBJECTIVE
Our objective was to investigate whether age and gender influence IHD prevalence, incidence, and mortality in people with SCH.


METHODS
Computerized (PubMed, EMBASE, and Cochrane Library) and manual searches of the literature to May 2007, published in English, were performed.


METHODS
Epidemiological studies that quantified thyroid status and IHD events in adults were performed.


METHODS
Two authors independently reviewed articles and abstracted data. Results were compared across two groups based on the minimum age of participants studied (younger than 65 yr and 65 yr or older).


RESULTS
There were 15 studies included for analysis with 2,531 SCH participants and 26,491 euthyroid individuals. IHD incidence and prevalence were higher in SCH subjects compared with euthyroid participants from studies including those younger than 65 yr, but not studies of subjects aged older than 65 yr [odds ratio (95% confidence interval)]: 1.57 (1.19-2.06) vs. 1.01 (0.87-1.18) and 1.68 (1.27-2.23) vs. 1.02 (0.85-1.22), respectively. Cardiovascular/all-cause mortality was also elevated in participants from the younger than 65-yr studies, but not from the studies of older people: odds ratio 1.37 (1.04-1.79) vs. 0.85 (0.56-1.29). Prevalent IHD was higher in SCH participants of both genders, although this was statistically significant only in women.


CONCLUSIONS
SCH is associated with increased IHD (both prevalence and incidence) and cardiovascular mortality only in subjects from younger populations. These data suggest that increased vascular risk may only be present in younger individuals with SCH.
Razvi
Salman
S
Department of Endocrinology, Queen Elizabeth Hospital, Gateshead, NE9 6SX, United Kingdom. salman.razvi@ghnt.nhs.uk
Shakoor
Abdul
A
Vanderpump
Mark
M
Weaver
Jolanta U
JU
Pearce
Simon H S
SH
D000367:Age Factors; D002318:Cardiovascular Diseases / Q000401:mortality; D003430:Cross-Sectional Studies; D006801:Humans; D007037:Hypothyroidism / Q000150:complications*; D015994:Incidence; D008137:Longitudinal Studies; D017202:Myocardial Ischemia / Q000453:epidemiology / Q000209:etiology*; D015995:Prevalence