Department of Anesthesiology, University of California, San Diego, USA.
Global Health Policy Institute, San Diego, USA.
BMC Public Health. 2021 Jul 5;21(1):1238. doi: 10.1186/s12889-021-11089-w.
Vitamin D has been identified as a potential protective factor in the development of colorectal cancer (CRC). We expect to see a stronger association of ultraviolet B (UVB) exposure and CRC crude rates with increasing age since chronic vitamin D deficiency leads to sustained molecular changes that increase cancer risk. The DINOMIT (disjunction, initiation, natural selection, overgrowth, metastasis, involution, and transition) model postulates various stages of cancer development due to vitamin D deficiency and the associated latency period. The purpose of this study is to examine this age-dependent inverse relationship globally.
In this ecological study, a series of linear and polynomial regression tests were performed between country-specific UVB estimates adjusted for cloud cover and crude incidence rates of CRC for different age groups. Multiple linear regression was used to investigate the association between crude incidence rates of colorectal cancer and UVB estimate adjusting for urbanization, skin pigmentation, smoking, animal consumption, per capita GDP, and life expectancy. Statistical analysis was followed by geospatial visualization by producing choropleth maps.
The inverse relationship between UVB exposure and CRC crude rates was stronger in older age groups at the country level. Quadratic curve fitting was preferred, and these models were statistically significant for all age groups. The inverse association between crude incidence rates of CRC and UVB exposure was statistically significant for age groups above 45 years, after controlling for covariates.
The age-dependent inverse association between UVB exposure and incidence of colorectal cancer exhibits a greater effect size among older age groups in global analyses. Studying the effect of chronic vitamin D deficiency on colorectal cancer etiology will help in understanding the necessity for population-wide screening programs for vitamin D deficiency, especially in regions with inadequate UVB exposure. Further studies are required to assess the need for adequate public health programs such as selective supplementation and food fortification.
维生素 D 已被确定为结直肠癌（CRC）发展的潜在保护因素。我们预计，随着慢性维生素 D 缺乏导致持续的分子变化从而增加癌症风险，紫外线 B（UVB）暴露与 CRC 粗发病率之间的关联将随着年龄的增长而增强。DINOMIT（分离、启动、自然选择、过度生长、转移、退化和转变）模型假设由于维生素 D 缺乏和相关的潜伏期，癌症发展有多个阶段。本研究的目的是在全球范围内检验这种年龄相关的反比关系。
在这项生态学研究中，我们对经过云层修正的国家特定 UVB 估计值与不同年龄组 CRC 粗发病率之间进行了一系列线性和多项式回归检验。多元线性回归用于调查调整城市化、皮肤色素沉着、吸烟、动物消费、人均 GDP 和预期寿命后，CRC 粗发病率与 UVB 估计值之间的关联。统计分析后，通过制作专题地图进行地理空间可视化。
在国家层面，UVB 暴露与 CRC 粗发病率之间的反比关系在年龄较大的年龄组中更强。二次曲线拟合是首选，并且所有年龄组的模型均具有统计学意义。在控制了协变量后，CRC 粗发病率与 UVB 暴露之间的负相关在 45 岁以上年龄组中具有统计学意义。
在全球分析中，UVB 暴露与结直肠癌发病率之间的年龄依赖性反比关系在年龄较大的年龄组中表现出更大的效应大小。研究慢性维生素 D 缺乏对结直肠癌病因学的影响将有助于理解进行人群范围的维生素 D 缺乏筛查计划的必要性，尤其是在紫外线 B 暴露不足的地区。需要进一步研究来评估是否需要适当的公共卫生计划，如选择性补充和食物强化。
