Unilateral Oophorectomy Before Menopause
Between 1950 and 2007, 1,838 women younger than 50 years and living in Olmsted County, MN, underwent UO. About 60% of the UOs occurred at the time of hysterectomy. Table 1 presents age-specific incidence rates for all women who underwent UO and for the subgroup of women who underwent UO concurrently with hysterectomy across six periods (five decades and eight additional years). Pooling all oophorectomies for the 58-year study period, we found that UO was more common than bilateral oophorectomy through the age of 39 years, at which time the incidence of bilateral oophorectomy surpassed that of UO (Figure 1A). The left ovary was removed more frequently than the right ovary for all ages (overall 55.3% left vs 44.7% right, P < 0.0001; Figure 1A), but particularly for women aged between 35 and 49 years.
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Figure 1.
Incidence rates for unilateral oophorectomy and bilateral oophorectomy in Olmsted County, MN, from 1950 to 2007. Incidence rates are shown across age groups (A; average age-specific incidence rates for a 58-y period) and across calendar year groups (B; calendar year-specific incidence rates). Incidence rates for unilateral oophorectomy are also shown separately for the left and right ovaries. Incidence rates across calendar year groups are agestandardized to the total population from the 2000 US Census. Data on the incidence of bilateral oophorectomy were derived from a previous study in Olmsted County, MN. Note that the y axis scale differs between (A) and (B).
Temporal trends of age-standardized incidence rates showed that a decrease in UO rates coincided with an increase in bilateral oophorectomy rates (Figure 1B). The incidence rates for UO increased from 1950 to 1974, but decreased after 1974. By contrast, bilateral oophorectomy was performed less frequently than UO from 1950 through 1969, was performed as frequently as UO from 1970 through 1984, and surpassed UO starting in 1985 (Figure 1B). Temporal trends also demonstrated a difference in the laterality of UO. Age-standardized incidence rates for left UO were higher than those for right UO from 1950 through 1984 (79.9 left vs 54.9 right per 100,000 person-years), but were similar in the most recent 23 years (34.5 left vs 34.6 right per 100,000 person-years; 1985-2007).
We divided the cohort into two age groups to approximate the premenopausal (0-39 y) and perimenopausal (40-49 y) periods. Left UO was performed more commonly than right UO in women aged 0 to 39 years until 1979 (45.4 left vs 34.4 right per 100,000 person-years; Figure 2A) and in women aged 40 to 49 years until 1989 (170.2 left vs 102.3 right per 100,000 person-years; Figure 2D).
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Figure 2.
Time trends in the incidence of unilateral oophorectomy by age group and laterality in Olmsted County, MN, from 1950 to 2007. A, D: Trends for all unilateral oophorectomies combined. B, E: Incidence of unilateral oophorectomy with an ovarian medical indication. C, F: Incidence of unilateral oophorectomy without a specified ovarian medical indication. Incidence is shown for women younger than 40 years (top; A-C) and women aged 40 to 49 years (bottom; D-F).
We investigated the time trends for women who underwent UO with or without concurrent hysterectomy. There was no clear trend among women younger than 40 years (Figure 3A). By contrast, among women aged 40 to 49 years, UO was more commonly performed concurrently with hysterectomy through 1989 (Figure 3B).
(Enlarge Image)
Figure 3.
Time trends in the incidence of unilateral oophorectomy by age group and hysterectomy status in Olmsted County, MN, from 1950 to 2007. Incidence is shown for women younger than 40 years (A) and women aged 40 to 49 years (B).
Figure 2B, E also shows the trends in laterality across time for women who had UO with a medical indication, divided into two age groups. In both age groups, the left ovary was removed more commonly than the right ovary through 1979. The most common indication for UO was a benign condition of the ovary for all women and for women with concurrent hysterectomy ( Table 2 ). Among women with concurrent hysterectomy, the right ovary was removed for a benign condition more frequently than the left ovary (69.6% right vs 63.3% left, P = 0.03; Table 2 ). All medical indications were similar in the right and left ovaries, except for "other" medical indications that were more common in the right ovary (3.0% right vs 1.5% left, P = 0.02).
Women who underwent UO without a medical indication were the second largest group by indication in the overall incident series (20.2%) and among women with concurrent hysterectomy (31.8%; Table 2 ). The left ovary was removed more frequently without a medical indication than the right ovary both in the overall group (22.8% left vs 17.0% right, P = 0.002; Table 2 ) and among women with concurrent hysterectomy (34.8% left vs 27.8% right, P = 0.01).In women aged 0 to 39 years without a medical indication, differences in laterality were small throughout the study period (Figure 2C). By contrast, in women aged 40 to 49 years, the left ovary was removed more commonly than the right ovary through 1989 (Figure 2F).
Table 3 shows the pathology found in the removed ovary across the entire study period, by laterality. In the overall group, cysts were the most common pathological finding and had similar frequencies on both sides (29.2% left vs 29.4% right, P = 0.92; Table 3 ). Apparently normal ovaries were the second most common pathological finding overall and occurred similarly in the right and left ovaries (19.4% left vs 19.5% right, P = 0.97). By contrast, endometriosis occurred more frequently in the left ovary than in the right ovary (19.0% left vs 13.4% right, P = 0.001). Although not statistically significant, primary ovarian cancer occurred more frequently in the right ovary than in the left ovary (1.5% right vs 0.7% left, P = 0.10). Other pathologies, such as ectopic pregnancy, were more common in the right ovary than in the left ovary (7.1% right vs 4.4% left, P = 0.01).
Table 3 also shows the pathology found in the ovary removed from women with or without a medical indication. The pathology differed by laterality among women with a medical indication for UO. Endometriosis was more common in the left ovary (23.9% left vs 15.8% right, P = 0.0001). "Other" pathologies were more common in the right ovary (7.8% right vs 4.7% left, P = 0.02). By contrast, most ovaries removed without a medical indication were apparently normal on pathological examination (52.2% left vs 55.7% right, P = 0.51),and pathology did not differ significantly by side ( Table 3 ).
Indication and resultant pathology were consistent. Of the 1,352 women with an indication of benign condition ( Table 2 ), 1,197 (88.5%) had pathology consistent with a benign process (eg, endometriosis or benign tumor). Among the remaining 155 women (11.5%), 137 had normal ovaries, 13 had ovarian cancer, and 5 had unknown pathology. Of the 12 women with an indication of primary or metastatic cancer, 8 women (66.7%) had primary or metastatic cancer confirmed by pathological examination.
Results
Age Patterns and Time Trends
Between 1950 and 2007, 1,838 women younger than 50 years and living in Olmsted County, MN, underwent UO. About 60% of the UOs occurred at the time of hysterectomy. Table 1 presents age-specific incidence rates for all women who underwent UO and for the subgroup of women who underwent UO concurrently with hysterectomy across six periods (five decades and eight additional years). Pooling all oophorectomies for the 58-year study period, we found that UO was more common than bilateral oophorectomy through the age of 39 years, at which time the incidence of bilateral oophorectomy surpassed that of UO (Figure 1A). The left ovary was removed more frequently than the right ovary for all ages (overall 55.3% left vs 44.7% right, P < 0.0001; Figure 1A), but particularly for women aged between 35 and 49 years.
(Enlarge Image)
Figure 1.
Incidence rates for unilateral oophorectomy and bilateral oophorectomy in Olmsted County, MN, from 1950 to 2007. Incidence rates are shown across age groups (A; average age-specific incidence rates for a 58-y period) and across calendar year groups (B; calendar year-specific incidence rates). Incidence rates for unilateral oophorectomy are also shown separately for the left and right ovaries. Incidence rates across calendar year groups are agestandardized to the total population from the 2000 US Census. Data on the incidence of bilateral oophorectomy were derived from a previous study in Olmsted County, MN. Note that the y axis scale differs between (A) and (B).
Temporal trends of age-standardized incidence rates showed that a decrease in UO rates coincided with an increase in bilateral oophorectomy rates (Figure 1B). The incidence rates for UO increased from 1950 to 1974, but decreased after 1974. By contrast, bilateral oophorectomy was performed less frequently than UO from 1950 through 1969, was performed as frequently as UO from 1970 through 1984, and surpassed UO starting in 1985 (Figure 1B). Temporal trends also demonstrated a difference in the laterality of UO. Age-standardized incidence rates for left UO were higher than those for right UO from 1950 through 1984 (79.9 left vs 54.9 right per 100,000 person-years), but were similar in the most recent 23 years (34.5 left vs 34.6 right per 100,000 person-years; 1985-2007).
We divided the cohort into two age groups to approximate the premenopausal (0-39 y) and perimenopausal (40-49 y) periods. Left UO was performed more commonly than right UO in women aged 0 to 39 years until 1979 (45.4 left vs 34.4 right per 100,000 person-years; Figure 2A) and in women aged 40 to 49 years until 1989 (170.2 left vs 102.3 right per 100,000 person-years; Figure 2D).
(Enlarge Image)
Figure 2.
Time trends in the incidence of unilateral oophorectomy by age group and laterality in Olmsted County, MN, from 1950 to 2007. A, D: Trends for all unilateral oophorectomies combined. B, E: Incidence of unilateral oophorectomy with an ovarian medical indication. C, F: Incidence of unilateral oophorectomy without a specified ovarian medical indication. Incidence is shown for women younger than 40 years (top; A-C) and women aged 40 to 49 years (bottom; D-F).
UO With or Without Hysterectomy
We investigated the time trends for women who underwent UO with or without concurrent hysterectomy. There was no clear trend among women younger than 40 years (Figure 3A). By contrast, among women aged 40 to 49 years, UO was more commonly performed concurrently with hysterectomy through 1989 (Figure 3B).
(Enlarge Image)
Figure 3.
Time trends in the incidence of unilateral oophorectomy by age group and hysterectomy status in Olmsted County, MN, from 1950 to 2007. Incidence is shown for women younger than 40 years (A) and women aged 40 to 49 years (B).
UO With Medical Indication
Figure 2B, E also shows the trends in laterality across time for women who had UO with a medical indication, divided into two age groups. In both age groups, the left ovary was removed more commonly than the right ovary through 1979. The most common indication for UO was a benign condition of the ovary for all women and for women with concurrent hysterectomy ( Table 2 ). Among women with concurrent hysterectomy, the right ovary was removed for a benign condition more frequently than the left ovary (69.6% right vs 63.3% left, P = 0.03; Table 2 ). All medical indications were similar in the right and left ovaries, except for "other" medical indications that were more common in the right ovary (3.0% right vs 1.5% left, P = 0.02).
UO Without Medical Indication
Women who underwent UO without a medical indication were the second largest group by indication in the overall incident series (20.2%) and among women with concurrent hysterectomy (31.8%; Table 2 ). The left ovary was removed more frequently without a medical indication than the right ovary both in the overall group (22.8% left vs 17.0% right, P = 0.002; Table 2 ) and among women with concurrent hysterectomy (34.8% left vs 27.8% right, P = 0.01).In women aged 0 to 39 years without a medical indication, differences in laterality were small throughout the study period (Figure 2C). By contrast, in women aged 40 to 49 years, the left ovary was removed more commonly than the right ovary through 1989 (Figure 2F).
Pathology of UO
Table 3 shows the pathology found in the removed ovary across the entire study period, by laterality. In the overall group, cysts were the most common pathological finding and had similar frequencies on both sides (29.2% left vs 29.4% right, P = 0.92; Table 3 ). Apparently normal ovaries were the second most common pathological finding overall and occurred similarly in the right and left ovaries (19.4% left vs 19.5% right, P = 0.97). By contrast, endometriosis occurred more frequently in the left ovary than in the right ovary (19.0% left vs 13.4% right, P = 0.001). Although not statistically significant, primary ovarian cancer occurred more frequently in the right ovary than in the left ovary (1.5% right vs 0.7% left, P = 0.10). Other pathologies, such as ectopic pregnancy, were more common in the right ovary than in the left ovary (7.1% right vs 4.4% left, P = 0.01).
Table 3 also shows the pathology found in the ovary removed from women with or without a medical indication. The pathology differed by laterality among women with a medical indication for UO. Endometriosis was more common in the left ovary (23.9% left vs 15.8% right, P = 0.0001). "Other" pathologies were more common in the right ovary (7.8% right vs 4.7% left, P = 0.02). By contrast, most ovaries removed without a medical indication were apparently normal on pathological examination (52.2% left vs 55.7% right, P = 0.51),and pathology did not differ significantly by side ( Table 3 ).
Indication and resultant pathology were consistent. Of the 1,352 women with an indication of benign condition ( Table 2 ), 1,197 (88.5%) had pathology consistent with a benign process (eg, endometriosis or benign tumor). Among the remaining 155 women (11.5%), 137 had normal ovaries, 13 had ovarian cancer, and 5 had unknown pathology. Of the 12 women with an indication of primary or metastatic cancer, 8 women (66.7%) had primary or metastatic cancer confirmed by pathological examination.
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