Vercellini Paolo, Buggio Laura, Somigliana Edgardo, Dridi Dhouha, Marchese Maria Antonietta, Viganò Paola
Istituto Ostetrico e Ginecologico 'Luigi Mangiagalli', Department of Clinical Science and Community Health, Università degli Studi, Milano, Italy
Istituto Ostetrico e Ginecologico 'Luigi Mangiagalli', Department of Clinical Science and Community Health, Università degli Studi, Milano, Italy.
Hum Reprod. 2014 Oct 10;29(10):2171-5. doi: 10.1093/humrep/deu169. Epub 2014 Jul 8.
Is the prevalence of blue eye colour higher in women with deep endometriosis?
Blue eye colour is more common in women with deep endometriosis when compared with both women with ovarian endometriomas and women without a history of endometriosis.
Recent and intriguing evidence suggests that women with deep endometriosis may have particular phenotypic characteristics including a higher prevalence of a light-colour iris. Available epidemiological evidence is however weak.
STUDY DESIGN, SIZE, DURATION: Case-control study performed in a large academic department specializing in the study and treatment of endometriosis. Individual iris colour was evaluated in daylight and categorized in three grades, namely blue-grey (blue), hazel-green (green) and brown. One observer assessed iris colour. In addition, the women themselves were invited to indicate the colour of their eyes according to the same classification system. Cases with discordant eye colour determinations between the observer and the woman were excluded from the final analysis.
PARTICIPANTS MATERIALS, SETTINGS, METHODS: Two hundred and twenty-three women with deep endometriosis (cases), 247 with ovarian endometriomas and 301 without a history of endometriosis were enrolled.
After exclusion of 52 discordant cases, the proportions of brown, blue and green eye colours were, respectively, 61, 30 and 9% in the deep endometriosis group, 74, 16 and 10% in the endometrioma group and 75, 15 and 10% in the non-endometriosis group. Women in the deep endometriosis group had a statistically significant excess of blue eyes and a reduced proportion of brown eyes compared with the two control groups (P = 0.002 and P < 0.001, respectively). The proportion of blue eyes was almost identical in the ovarian endometrioma group and the non-endometriosis group, and that of green eyes was substantially similar in all study groups. The OR (95% CI) of having blue eyes in women with deep endometriosis compared with women with ovarian endometriosis and with those without endometriosis was, respectively, 2.2 (1.4-3.6) and 2.5 (1.6-3.9).
LIMITATIONS, REASON FOR CAUTION: We cannot exclude that some women without a previous diagnosis of endometriosis indeed had the disease. However, this would have led to a reduction of the observed difference in proportion of blue eyes, thus to a potential underestimation of the real strength of the association. Moreover, under-ascertainment is possible with regard to peritoneal disease, but unlikely with deep endometriotic lesions and ovarian endometriomas.
There are two possible explanations for our findings. Both may have intriguing implications for future research on endometriosis. Firstly, genes involved in the control of iris colour transmission may lie in a region with a strong pattern of linkage disequilibrium with genes involved in the invasiveness of endometriosis. Alternatively, blue eye colour could be considered an indicator of a photo-sensitive phenotype resulting in limited exposure to sunlight and UVB radiation. Limited sunlight exposure is associated with reduced circulating 25-hydroxyvitamin D3, an element that has recently been linked to endometriosis development.
深部子宫内膜异位症女性中蓝眼睛颜色的患病率是否更高？
与患有卵巢子宫内膜异位囊肿的女性和无子宫内膜异位症病史的女性相比，蓝眼睛颜色在深部子宫内膜异位症女性中更为常见。
近期有有趣的证据表明，深部子宫内膜异位症女性可能具有特定的表型特征，包括浅色虹膜的患病率较高。然而，现有的流行病学证据较为薄弱。
研究设计、规模、持续时间：在一个专门研究和治疗子宫内膜异位症的大型学术科室进行的病例对照研究。在自然光下评估个体虹膜颜色，并分为三个等级，即蓝灰色（蓝色）、淡褐色 - 绿色（绿色）和棕色。由一名观察者评估虹膜颜色。此外，邀请女性自身根据相同的分类系统指出她们眼睛的颜色。观察者与女性之间眼睛颜色判定不一致的病例被排除在最终分析之外。
参与者、材料、设置、方法：招募了223名深部子宫内膜异位症女性（病例组）、247名患有卵巢子宫内膜异位囊肿的女性和301名无子宫内膜异位症病史的女性。
排除52例不一致病例后，深部子宫内膜异位症组中棕色、蓝色和绿色眼睛的比例分别为61%、30%和9%，子宫内膜异位囊肿组为74%、16%和10%，非子宫内膜异位症组为75%、15%和10%。与两个对照组相比，深部子宫内膜异位症组女性蓝眼睛比例在统计学上显著更高，棕色眼睛比例更低（分别为P = 0.002和P < 0.001）。卵巢子宫内膜异位囊肿组和非子宫内膜异位症组中蓝眼睛比例几乎相同，所有研究组中绿色眼睛比例基本相似。深部子宫内膜异位症女性与患有卵巢子宫内膜异位症的女性以及无子宫内膜异位症的女性相比，拥有蓝眼睛的OR（95%CI）分别为2.2（1.4 - 3.6）和2.5（1.6 - 3.9）。
局限性、谨慎原因：我们不能排除一些之前未诊断出子宫内膜异位症的女性实际上患有该病的可能性。然而，这会导致观察到的蓝眼睛比例差异减小，从而可能低估关联的实际强度。此外，对于腹膜疾病可能存在漏诊情况，但对于深部子宫内膜异位病变和卵巢子宫内膜异位囊肿则不太可能。
对于我们的研究结果有两种可能的解释。两者可能都对未来子宫内膜异位症的研究具有有趣的启示。首先，参与虹膜颜色传递控制的基因可能位于与参与子宫内膜异位症侵袭性的基因具有强连锁不平衡模式的区域。或者，蓝眼睛颜色可被视为光敏表型的一个指标，导致阳光和紫外线B辐射暴露有限。阳光暴露有限与循环25 - 羟维生素D3减少有关，而这一元素最近已与子宫内膜异位症的发展相关联。
