Smoking Rates Decline, Yet Lung Cancer Cases Surge by Tens of Thousands? Report Reveals Cancer Risk Factors, Incidence in Southern Regions Over 10 Times Higher Than in the North?

Smoking is harmful to health. In recent years, Japan's smoking rate has steadily declined. According to surveys by the Ministry of Health, Labour and Welfare, the smoking rate among adult males has halved compared to two decades ago, while the rate among females has also gradually decreased. However, paradoxically, both the number of deaths and new cases of lung cancer continue to rise annually. In 2023, lung cancer remained the leading cause of cancer-related deaths, claiming approximately 80,000 lives per year. The number of new cases has surpassed 100,000 annually, continuing an upward trend contrary to the decline in smoking rates.

Several factors may explain this phenomenon. First, smoking has a long latency period. Many patients currently diagnosed with lung cancer belong to generations who smoked decades ago, meaning past smoking habits are now manifesting as current disease. Second, the impact of secondhand smoke cannot be ignored. Particularly among older women, exposure to spousal secondhand smoke remains a major risk factor. Third, non-smoking risk factors—such as air pollution, occupational exposure (e.g., asbestos), genetic predisposition, and the aging population—are becoming increasingly significant.

Another critical finding is the stark regional disparity. Analyses show that age-adjusted lung cancer incidence rates in southern prefectures, including Kyushu and Okinawa, are over ten times higher than in the Tohoku and Kanto regions. This difference is statistically significant and unlikely to be due to chance alone. Contributing factors may include regional differences in smoking rates (still higher in the south), industrial structure (concentration of heavy industry and manufacturing), variations in air quality, disparities in access to medical care, and differences in cancer screening participation rates.

Experts recommend that future strategies go beyond smoking prevention to include strict secondhand smoke control, air pollution monitoring and mitigation, workplace safety measures, targeted cancer screening programs in high-risk areas, and the introduction of personalized medicine based on genetic risk. There is a strong call for comprehensive health initiatives, especially in southern regions.