| BackgroundWith the aging of the population in our country, more attention is drawn to thehealth-care of older people. Thyroid diseases are common endocrine diseases, andthyroid dysfunction is particularly common in elderly population. Previous studieshave shown severity of cerebral atrophy and infarct-like vascular damage in elderlymen is associated with increasing thyroid stimulating hormone (TSH) level evenwithin the reference range. At present there are few research and reports on thyroiddiseases in elderly population. Therefore, prevention and treatment of thyroiddiseases among elderly people should be attached widely attention. Legislation hasbeen implemented to eliminate iodine deficiency diseases and universal saltiodization (USI) campaign was launched throughout the country in 1996. Whilst wehave reached the goal of eliminating iodine deficiency diseases, the thyroid diseasescope and prevalence has changed dramatically as a result of the increase of iodineintake, which drew much attention of thyroid science field nationally and intemationally. Apart from the effect of iodide ion on thyroid diseases, smoking, anda number of physical and chemical factors are gradually getting more attention. TheGuangzhou Biobank Cohort Study (GBCS), a collaboration of Guangzhou Number12 Hospital, Department of Community Medicine, the University of Hong Kong,Hong Kong, and Department of Public Health and Epidemiology, the University ofBirmingham, UK, provided an excellent platform to acquire the information oniodine nutrition, to estimate the prevalence of thyroid diseases and to investigaterelative risk factors in elderly people. In this report, the baseline data of GBCS(September 2003 to October 2006) was used, with additional information from testsof urinary iodine and thyroid function parameters as well as the family history ofthyroid diseases. The author is one of the main investigators of GBCS, responsiblefor coordination and inspection of the study field and data management.Objectives1. To investigate the situations of current iodine nutrition, abnormal thyroidfunction and goiter among elderly population after USI, and to explore therelevant impacting factors;2. To investigate the past and the current prevalence of thyroid diseases in elderlypopulation, specifically on the effects of sex, family history, reproductive historyand occupational exposure to certain physical and chemical factors on thyroiddiseases;3. To investigate the prevalence of cardiovascular diseases, gastrointestinal diseasesand eye diseases among subjects with thyroid diseases history;4. To provide evidence and basis for setting up policies of iodine nutrition andthyroid disease prevention and treatment in Guangzhou.MethodsWe measured the urine iodine level, thyroid function, goiter and thyroid disease history among elderly Guangzhou residents aged＞50 years cross-sectionally, andadministered a face to face interview with a computerized questionnaire to obtaininformation on potential impacting factors. Ion chromatography was used tomeasure urinary iodine for 569 subjects. Thyroid function parameters weremeasured by equipment and corresponding materials by Abbott Company for 1139subjects. Thyroid palpation was used for 20044 subjects. Thyroid disease andcardiovascular disease histories were acquired for 20163 subjects. SPSS 10.0.1was used for all the analyses in this report.Results1. Situations of iodine nutrition[1] A standard equation on urinary iodine measurement using ion chromatographywas established. A=0.249C+3.303 (where A: peak area×10~5, C: concentrationof iodine,μg/L). Correlation coefficient, r=0.999903;[2] Urinary iodine has a positively skewed distribution among elderly population inGuangzhou(≥50 years), with a median of 223.2μg/L; 10.4% of the subjects hadiodine deficiency (＜100μg/L) and 28.8% had excessive iodine intake(＞300μg/L);[3] Urinary iodine level was different to some extent in subjects with differenteducational level, occupation and living areas.2. Thyroid function[1] The prevalence of thyroid dysfunction was 9.0%(103/1139), clinical prevalenceand sub-clinical prevalence were 0.4% (5/1139) and 8,6% (98/1139)respectively. Among subjects with thyroid dysfunction, 72 subjects wereidentified as sub-clinical hyperthyroidism (69.9%), 26 subjects were identifiedas sub-clinical hypothyroidism (25.2%), 1 subject was identified overt clinicalhyperthyroidism (1.0%) and 4 subjects were identified overt clinical hypothyroidisms (3.9%);[2] The prevalence Of thyroid dysfunction increased significantly with age, P=0.007,the odds ratio (OR) for subjects aged≥70 was 2.28 compared to those aged50-59 (95%CI 1.27-4.09);[3] The risk of thyroid dysfunction increased significantly among subjects withthyroid diseases history compared with those without thyroid disease history(OR 2.93, 95%CI 1.64-5.26);[4] Excessive iodine intake was associated with an increase in prevalence of thyroiddysfunction. The OR for those with excessive iodine intake was 2.27 (95%CI1.12-4.60) compared with subjects with normal or deficient iodine intake;[5] Smokers had a higher prevalence of thyroid dysfunction. The risk of thyroiddysfunction increased in men from never smokers, former smokers to currentsmokers (P=0.035), and increased with smoking years and amount of dailysmoking (P=0.007 and P=0.009 respectively), but decreased with increasingquitting years (P=0.006). The risk of thyroid dysfunction for current smokerswere 2.79 times (95%CI 1.11-7.02) of never smokers;[6] The prevalence of goiter among subjects with abnormal thyroid function was10.7%, much higher than those with normal thyroid function (3.4%), P=0.002.3. Goiter[1] The prevalence of goiter was 3.1% (623/20044), with women (3.8%, n=543)higher than men (1.4%,n=80), P＜0.001;[2] The risk of having goiter was 6.84 times higher among subjects with thyroiddisease histories than those without such histories (95%CI 5.75-8.15);[3] The prevalence of thyroid dysfunction among subjects with goiter was 23.9%,much higher than those without goiter (8.4%), P=0.002.4. The prevalence history of thyroid diseases [1] Overall, 10.1% (2042/20163)of the subjects reported thyroid diseases histories,the prevalence was 3.2 times significantly higher in women (12.6%,n=1808)than men (4.0%,n=234), P＜0.001; The prevalence of thyroid diseases was 3.5%(713/20163), with women 4.3% (n=612) significantly higher than men 1.7%(n=101), P＜0.001;[2] The mean age of disease onset was 43±14 years, with women significantlyearlier (42±14 years) than men (48±14 years), P＜0.001; The onset ofhyperthyroidism, goiter and thyroid tumor were similarly earlier, buthypothyroidism had a late onset with mean age of 51±12 years. It was 9 yearslater than that of hyperthyroidism, P＜0.001.[3] The overall prevalence of thyroid diseases increased from no thyroid diseasehistory, history in one generation to history in two generations, P＜0.001 in bothmale and female. The prevalence of thyroid diseases among those with diseasehistory in both generations was 40.0% in men and 50.0% in women,significantly higher than those with history in one generation (7.1% in men and27.7% in women) and those without any thyroid disease history (3.0% in menand 10.3% in women);[4] The prevalence of thyroid diseases increased significantly in subjects withoccupational exposure to chemical (manganese, lead and its compounds, someorganic solvents) and physical factors (noise); The prevalence was higher insubjects with severe exposure than mild to moderate exposure(self-report);[5] The prevalence of thyroid diseases among women who breastfed was 4.3%,significantly higher than those without breastfeeding(2.3%), P=0.036; But theprevalence decreased with the duration of breastfeeding, breastfeeding firstchild P=0.024, second child P=0.048;[6] The prevalence of cardiovascular diseases, gastrointestinal diseases, eye diseases and abnormal ECG were significantly higher in subjects with thyroiddiseases history(47.3%,31.4%,36.0% and 69.2% respectively) compared withsubjects reporting no thyroid disease history (41.3%,26.1%,29.4% and 53.8%respectively), P＜0.001 for all.Conclusions1. The ion chromatography method used to test urinary iodine in this study wasefficient, stable and had high sensitivity, and is suitable to be used in generalpopulation;2. The iodine nutrition is more than adequate among elderly population inGuangzhou. However, it should be noted that nearly 30% of the subjects hadexcessive iodine intake;3. Sub-clinical abnormality, especially the sub-clinical hyperthyroidism is the mostcommon type of thyroid dysfunction among Guangzhou elderly population.Hypothyroidism is mainly manifested as overt clinical abnormality;4. The proportion of thyroid function abnormality increased significantly with age;5. Excessive intake of iodine and smoking were associated with thyroid functionabnormality, with a dose-response relationship between smoking and thyroidfunction abnormality;6. The prevalence of thyroid function abnormality and goiter increasedsignificantly in subjects with thyroid disease history;7. Goiter is significantly associated with thyroid function abnormality;8. The prevalence of thyroid diseases in women is significantly higher than that inmen.;9. Hypothyroidism has a late disease onset;10. There is a clear family aggregation in thyroid diseases;11. Breast feeding and occupational exposure to some hazardous physical and chemical agents were associated with thyroid diseases;12. The proportion of cardiovascular diseases, gastrointestinal diseases, eye diseasesand ECG abnormalities were higher in subjects with thyroid disease history thanthose without.In a word, though iodine nutrition in those Guangzhou residents aged 50 or abovewas more or less adequate, those who had excessive iodine intake accounted fornearly 30%, almost 3 times of those who had iodine deficiency. The prevalence ofthyroid dysfunction was 9.0%, increasing with age. Excessive iodine intake andtobacco smoking were also associated with thyroid dysfunction. The prevalence ofthyroid diseases was higher in female than in male. Pregnancy, family history ofthyroid diseases and occupational hazard exposure were associated with sufferingfrom thyroid diseases. Those who had thyroid diseases history appeared to have ahigher chance of having cardiovascular diseases, chronic gastrointestinal diseasesand eye diseases. Results indicate that it should be thought much of the thyroidfunction and diseases for the elderly people, and further assessment is needed toestablish the optimal iodine intake for the elderly population.
|
PDF Full Text Request