To assess trends in prevalence of total and diagnosed diabetes, and in the probability of detecting undiagnosed diabetes in the Swiss population.
The Bus Santé study is an annual cross-sectional study of adults residing in Geneva state, Switzerland. We included 8532 participants (51% women) from the years 2005 to 2017, when fasting plasma glucose data became available. Total diabetes was defined as the sum of diagnosed and undiagnosed diabetes, while diagnosed diabetes was defined as having a previous diagnosis, and undiagnosed diabetes as having fasting plasma glucose level of ≥7 mmol/l and no previous diagnosis. We calculated the probability of finding undiagnosed diabetes among participants without a diagnosis. We examined for linear and quadratic trends, grouping survey years into five survey periods.
In total, 711 diabetes cases were identified over 13 years. The age- and gender-standardized prevalence of total diabetes decreased between the periods 2005-2009 and 2012-2013 from 9.6% (95% CI 8.3, 10.9) to 7.1% (95% CI 5.8, 8.4), but increased to 8.6% (95% CI 7.3%, 9.9%) by 2016-2017 (P-quadratic <0.01). For diagnosed diabetes, the prevalence decreased between 2005-2009 and 2014-2015 from 8.3% (95% CI 7.0%, 9.5%) to 6.1% (95% CI 5.0%, 7.2%), but increased slightly again to 7.0% (95% CI 5.8%, 8.2%) by 2016-2017 (P-quadratic = 0.01). Men generally had a higher prevalence of total and diagnosed diabetes than women, except in 2016-2017, when the prevalence of total diabetes was 9.5% (95% CI 7.6, 11.5) among men and 7.7% (95% CI 6.0, 9.5) among women (P >0.05). The probability of finding undetected diabetes among participants without a diabetes diagnosis decreased slightly between 2005-2009 and 2012-2013 from 1.5% (95% CI 0.9, 2.0) to 1.0% (95% CI 0.5, 1.5), but increased afterwards to 1.7% (95% CI 1.0, 2.3) by 2016-2017 (P-quadratic = 0.06); in 2016-2017, it was 2.6% (95% CI 1.5, 3.7) among men and 0.7% (95% CI 0.1, 1.3) among women (P <0.01).
The prevalence of diabetes has remained relatively constant over time. However, the probability of finding undetected cases of diabetes in the population without diabetes may be increasing among men.