Impact of a national screening programme on obesity and cardiovascular risk factors

In this national cohort of 5 819 041 men and women in Japan, we provide robust evidence that nationwide assignment to the health guidance resulted in only a small reduction in obesity parameters in men and women which was lost within only a few years. Exposure to the health guidance also failed to lead to long-term changes in cardiovascular risk factors and lifestyle behaviours. Japan is the only country with large populace across the globe that provides the annual prevention programme, and thus this study renders unique results of international importance. Aims The benefits of nationwide screening and tailored health guidance on improving obesity and cardiovascular risk factors is uncertain. The aim of the present study was to investigate the association of the national health screening and tailored health guidance with population health outcomes. Methods and results A fuzzy regression discontinuity design analysed data of men and women aged 40-74 years who participated in a nationwide health screening programme in Japan from 1 April 2008 to 31 March 2019 and were recorded in the Japanese National Database. Exposure was assignment to the national health guidance of counselling on healthy lifestyle and clinical follow-up for individuals found to have waist circumference >= 85 cm for men >= 90 cm for women with one or more cardiovascular risk factors during annual national health screening. The primary outcomes were changes in obesity status and cardiovascular risk factors 1 year after screening. Of 3 490 112 men and 2 328 929 women, the assignment to the health guidance resulted in small reductions in obesity parameters: waist circumference; men, -0.27 cm [95% confidence interval (CI) -0.29 to -0.26]; women -0.34 (-0.41 to -0.27); body mass index, -0.07 kg/m(2) (-0.075 to -0.066); -0.11 kg/m(2) (-0.13 to -0.10); weight, -0.21 kg (-0.22 to -0.19); -0.28 kg (-0.32 to -0.24) that attenuated over time. Short-term improvements were also observed in blood pressure, haemoglobin A1c, fasting glucose and triglycerides across both sexes. Conclusion A nationwide health screening programme was associated with only small, and transient improvements in obesity and cardiovascular risk factors.