Incidence trends and environmental determinants of type 1 diabetes in Lithuania and Sweden

Abstract: Variation of diabetes incidence over time in countries with different incidence levels and socio-economic conditions, and in an age span beyond the childhood years, may give clues for diabetes causes.Materials: Data from prospective type 1 diabetes registers in Sweden and Lithuania in children (0-14 years) and young adults (15-34 and 15-39 years, respectively). Number of infections recorded in health care booklets (117 cases; 270 controls); interview about the dietary intake one-year before the diagnosis and routinely recorded growth data (99 cases; 180 controls).Results: The incidence of type 1 diabetes in Sweden and Lithuania differed most in the younger age groups, 28.9 and 7.5/100,000/year in 0-14-year group, respectively. During 1983-2000 incidence increased in 0-14-year old children in both countries, but the pattern of change differed. During 1983-1998 the incidence increased in Swedish children, but tended to decrease in young adults, with no increase in the age group below 35 years, indicating that the increase of childhood diabetes may be due to a shift towards a younger age at diagnosis. Within a low-incidence country Lithuania there was an urban-rural gradient of incidence, especially in the younger age groups, that seemed to follow poverty distribution: incidence in the 0-39-year group was 7.1, 9.0 and 8.8/100,000/year in rural areas, towns and cities, respectively, p<0.001.Exposure to one or more non-specific infection during the first half-year of life reduced diabetes risk: odds ratios (95%-CI) in 0-14 and 5-14-year groups were (0.60; 0.37-0.98) and (0.47; 0.26-0.87), respectively. Higher energy intake and weight-for-age were independent diabetes risk factors: odds ratios for medium and high levels of energy were 1.33 (0.52-3.42) and 5.23 (1.67-16.38), and for weight-for-age 3.20 (1.30-7.88) and 3.09 (1.16-8.22), respectively. High intake of carbohydrates, disaccharides and sucrose in particular, increased diabetes risk independently of the high intake of energy.Conclusion: Environmental factors associated with socio-economic conditions in childhood may be important for the occurrence of type 1 diabetes. Lack of exposure to microbial antigens early in life, higher intake of energy and more rapid growth may contribute to the increase of childhood-onset diabetes observed in many countries.