Age- and gender-dependent urinary iodine concentrations in an area-covering population sample from the Bernese region in Switzerland

Objective: Before a scheduled increase of salt iodide content up to 20 p.p. m. in Switzerland, urinary iodine concentration (UIC, mug/l) of a randomly selected, area-covering, age-stratified population subgroup was sampled in spring 1997, In contrast to former published. studies on UIC, we minimized biases by age, Sender, rural/urban, socio-economic and cultural influences. Methods: We contacted 750 households in the Bernese region using random tel ephone numbers. Per household, one proband selected by play dice collected a spot urine sample. We defined ser;en age categories: infants, children, a dolescents, adults I-III and seniors, aged 0-5, 6-12, 13-20, 21-35, 36-50, 51-65 and >65 years respectively Randomized UIC data were compared with WHO criteria of iodine deficiency (ID) and previous non-randomized, age-depend ent Swiss UIC data. To recruit a perfect random group of volunteers proved difficult, as study participation of adolescent and male populations was so mewhat lower than that of elder and female (P < 0.005) populations respecti vely, Study participation of inhabitants of rural and suburban regions was comparable (P = 0.139). Out of 413 obtained urine spots, 412 (55%) were ana lyzed statistically (58% women, 42% men, P < 0.005). Results: Ninety per cent of all UIC values ranged between 25 and 200 mug/l. Median UIC showed mild ID (94 mug/l). UIC varied significantly between age categories (P = 0.0006). Women had lower UIC than men (P = 0.014). Infants had no ID. Women in child-bearing age (13-35 years), adults II, adults III and seniors had mild ID. Compared with recommended supplies of 150 and 200 mug I/day in children and male adolescents respectively, we consider their UIC (110 and 144 mug/l) as at least borderline deficient, Absolute UIC was lowest in seniors. Probands from rural/suburban households had similar UIC s. Our UIC data were comparable to published ones. Conclusions: Despite long-term national efforts with iodized salt (15 p.p.m . in 1997), mild ID still prevailed in Bern in spring 1997, with rare extre me UIC values. Mild ID with women in child-bearing age land probably also w ith children and male adolescents) was a serious concern, as goiter growth with puberty or pregnancy might be the consequence. Mild ID in adults and s eniors might be due to restricted NaCl intake. Results of our randomly sele cted subgroup from a 650 000 population show that age- and gender-dependenc y are important when comparing our collected data with published UIC data. This fact must be considered with non-randomly selected population subgroup s.