Association between metabolic syndrome and participation in colorectal cancer screening in Japan: A retrospective cohort analysis using LIFE study data

1Introduction

The worldwide prevalence of colorectal cancer (CRC) is increasing, with an estimated 1.9 million new cases in 2020 and a projected 3.2 million new cases in 2040 [1] . In Japan, the number of CRC patients decreased slightly from 158,117 in 2016–155,625 in 2019 [23] . Nevertheless, CRC remains one of Japan’s most prevalent cancers. In 2019, CRC accounted for 27,416 deaths in men and 24,404 deaths in women, and was the leading cause of cancer deaths among women [23] .

Many cases of CRC present without symptoms in the early stages, and routine screening is recommended for at-risk persons. However, CRC screening participation rates in Japan remain low at 47.8 % for men and 40.9 % for women aged 40–69 years in 2019 [4] . The Japanese Ministry of Health, Labour and Welfare recommends CRC screening for individuals aged ≥ 40 years [5] . The risk factors of CRC include excess consumption of animal protein and fat due to the westernization of dietary habits [67] , lack of exercise [8] , obesity [9] , tobacco use [10] , and alcohol consumption [11] . These factors are related to lifestyle, which highlights the importance of CRC screening for persons with poor health habits. The continuation of such habits over time can culminate in the development of metabolic syndrome, which presents as a set of cardiovascular risk factors.

The Japanese government has implemented a nationwide screening program to identify individuals with metabolic syndrome in order to prevent lifestyle-related diseases. Under this program, all healthcare insurers are required to offer “Specific Health Checkups” to adults aged 40–74 years every year. Eligible adults may choose to participate in these annual checkups for free or at low cost. People who are identified as having metabolic syndrome during Specific Health Checkups are offered “Specific Health Guidance”, which is an advice-based intervention aimed at improving lifestyle habits that is administered by physicians, public health nurses, and dietitians 121314 . There is considerable overlap between the risk factors of metabolic syndrome and those of CRC, including diet, lack of exercise, tobacco use, alcohol consumption, and obesity 151617 . Consequently, people with metabolic syndrome constitute a high-risk group for CRC.

Interventions for lifestyle-related diseases in Japan mainly focus on their prevention, and people with metabolic syndrome are encouraged to routinely undergo cancer screening. Despite nationwide accessibility to the Specific Health Checkup and Specific Health Guidance system, it is unclear as to whether people with metabolic syndrome have higher CRC screening participation than those without metabolic syndrome. To our knowledge, no studies to date have evaluated the association between metabolic syndrome and CRC screening participation. We hypothesized that being diagnosed with metabolic syndrome would modify a person’s health behavior into participating in CRC screening. To test this hypothesis, we investigated if metabolic syndrome is associated with CRC screening participation in Japan.