Comparison Between Rural and Urban Populations in the Berne and the Ticino Regions

Short Communication Iodine supply in different geographical areas of Switzerland: comparison between rural and urban populations in the Berne and the Ticino regions

B SolcaÁ1, SE Jaeggi-Groisman1, V Saglini2 and H Gerber1*

1Department of Clinical Chemistry, University Hospital, Inselspital, CH-3010 Berne; and 2Bleniese Hospital, CH-6716-Acquarossa, Switzerland

Objective: We studied the question of possible regional differences of iodine intake in the population of rural and urban areas north and south of the Alps. Design: Transversal study. Setting: Six different regions from northern (Canton Berne) and southern Switzerland (Canton Ticino). Subjects: For each region 30 individuals were studied. Results: While signi®cant differences of urinary iodine between some regions were found (range from 79 mg iodine=g creatinine in Chiasso to 130 mg iodine=g creatinine in the Maggia Valley), no signi®cant differences between rural and urban populations of north and south of Switzerland were observed. Mild iodine de®ciency affected 35%, moderate iodine de®ciency 12% and severe iodine de®ciency 0.6% of the total population investigated. Conclusions: 49% of this population showed at least mild or moderate iodine de®ciency. The mean urinary iodine was just at the lower recommended limits. Signi®cant differences were found between individual regions (such as Chiasso and the Valley of Maggia), but not generally between rural and urban areas in the north and south of the Alps. Sponsorship: University Hospital, Inselspital, Berne. Descriptors: iodine; urinary iodine; iodine de®ciency; iodine supply; dietary intake

Introduction Switzerland (BuÈrgi et al, 1990). In addition to the correction of ID, the iodization of salt leads to decreased incidence of Iodine de®ciency (ID) continues to be a major public health thyrotoxicosis due to toxic nodular goitre (BuÈrgi et al, 1998). problem worldwide (Hetzel & Dunn, 1989; Gaitan & Dunn, The aim of this study is to detect differences in iodine supply 1992). It manifests in most affected areas as endemic goitre, and iodine consumption between the population from north- endemic cretinism, neonatal hypothyroidism, irreversible ern and southern Switzerland, and between the inhabitants of mental retardation and other developmental abnormalities urban and rural areas. (Hetzel & Dunn, 1989). The implementation of an iodization program has been shown to prevent endemic cretinism, and Material and methods reduce fetal and infant mortality in the community ( (Gaitan & Dunn, 1992). ID in Europe is still prevalent in countries with The study was carried out in six different regions: in insuf®cient iodine supplementation, such as Germany, Italy, northern Switzerland (Canton Berne) we chose the city of Spain, Portugal, Greece, Italy, Poland, Romania, Spain and Berne and the Emmental region; in southern Switzerland Turkey (Delange et al, 1993). Iodine prophylaxis started in (Canton Ticino) we compared cities such as Chiasso and Switzerland in 1922 by the addition of 5 mg Kl=kg to house- Mendrisio with the Blenio, Verzasca and the Maggia hold salt, but until 1962 the dose utilized was not suf®ciently valley. Subjects were recruited by personal contact. Each effective. Due to the progressive iodization of salt (5, 10, sample group consisted of 30 individuals residing within 20 mg KI=kg, representing 3.8, 7.6 and 15 mg iodide per kg in the six selected regions. Subjects were asked to ®ll in a the years 1922, 1965, 1980), ID has nearly disappeared in questionnaire. The answers documented age, sex, medication, drug intake and work place. *Correspondence: Professor H Gerber, Department of Clinical Chemistry, To assess the iodine supply we determined the urinary University Hospital, Inselspital, CH-3010 Berne, Switzerland. excretion, using a method based on the Sandell ± Kolthoff Email: [email protected] reaction modi®ed by Wawschinek and our own laboratory Contributors: Barbara SolcaÁ was the principal investigator, who (Haldimann et al, 1998). participated in the conception and design, managed the data collection and ®eld activities, and wrote the ®rst drafts. Silvia E. Jaeggi-Groisman Urinary sodium and creatinine were measured automati- contributed to statistical analysis, interpretation of the results and in the cally with a Hitachi 911 (Boehringer Mannheim, Germany). writing and editing of the manuscript. Valerio Saglini was involved in the ®eldwork. Hans Gerber is the guarantor who designed and coordinated the Results study, supervised ®eld activities and data management and had overall responsibility for interpretation and preparation of the paper. Table 1 shows the mean urinary iodine concentration as Received 13 January 1999; revised 6 May 1999; accepted 9 May 1999 well as the corresponding percentage of subjects with Iodine supply in different areas of Switzerland B SolcÁa et al 755 Table 1 Mean urinary iodine concentration and corresponding percentage of subjects with urinary iodine concentrations 0 ± 25, 26 ± 50, 51 ± 80, and 80 mg iodine=g creatinine

Urinary iodine % of subjects % of subjects % of subjects % of subjects Region n mg=g creatinine 80 Normal 51 ± 80 Mild ID 26 ± 50 Moderate ID 0 ± 25 Severe ID

Ticino 100 104Æ 22 53 34 12 1 Chiasso 28 79Æ 37 39.3 35.7 25 0 Maggia 28 130Æ 73 78.6 17.8 0 3.6 Blenio 27 96Æ 32 51.9 44.4 3.7 0 Verzasca 17 110Æ 152 35.3 41.2 23.5 0 Berne 67 95Æ 5 49.3 13.4 0 Berne 34 92Æ 48 44.1 44.1 11.8 0 Emmental 33 99Æ 53 54.5 30.3 15.2 0 Ticino Berne 167 101Æ 17 51.5 35.3 12.6 0.6

urinary iodine concentrations of 0 ± 25, 26 ± 50, 51 ± 80, content in the household salt with a peak in the eighties due and > 80 mg iodine=g creatinine (cr). We have found that to the iodine supplement rise to 20 mg KI=kg salt, but since 35% of all the individuals show a mild ID (urinary iodine: the late eighties the mean iodine excretion has decreased for 50 ± 80 mg=g cr), 12% have values corresponding to a the ®rst time in this century (from 127 to 160 mg iodine=g cr to moderate ID (25 ± 50 mg=g cr). Signi®cant differences are 87 mg iodine=g cr in the mid-nineties (Als et al, 1994; Als et found between regions such as Chiasso and the Valley of al, 1995; Truong et al, 1997). The unchanged urinary sodium Maggia, but no difference is found between the north and excretion re¯ects the fact that the salt consumption has not the south of Switzerland, or rural and urban areas. changed signi®cantly in this decade. No differences were found between groups allocated Our data con®rm the presence of populations at risk of according to urinary iodine concentration related to age, ID disease in Switzerland on both sides of the Alps and in sex, and medication (data not shown). rural as well as urban areas. There is an urgent need to investigate the circumstances leading to this situation. Some factors leading to the actual situation in Switzerland Discussion could be the lack of adequate information to the general We started this study with the hypothesis that relevant population and especially in the border areas, changes in regional differences in iodine intake might exist and that distribution of food and eating habits. Based on this and the rural population may be at risk of developing ID since other studies (Als et al, 1995; Truong et al, 1997), the they are self-suf®cient communities where people grow iodine concentration in salt for human consumption has their own food or eat meat from their own animal stock. been raised to 20 ± 30 mg=iodide (26 ± 39 mg KI=kg) by the The data obtained show that this hypothesis was not Swiss government in January 1998. correct, since we realized immediately after the ®rst personal interviews that the inhabitants from rural communities Acknowledgements ÐThe authors wish to thank Mrs Murielle Groux for go to the nearby city to shop at the supermarket once or her excellent technical assistance. twice a week. 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