Objective
To determine, in a case-control study, whether pelvic organ prolapse (POP) is associated with overall lifetime physical activity (combined leisure, outdoor, household, occupational), and lifetime leisure, lifetime strenuous, and teen years strenuous activity.
Study Design
One hundred ninety-one POP cases (defined as maximal vaginal descent ≥1 cm below the hymen) and 191 age and recruitment-site matched controls (defined as maximal vaginal descent ≤1 cm above the hymen) between 39-65 years with no or mild urinary incontinence, were recruited chiefly from primary care clinics. Participants completed Lifetime Physical Activity and Occupation Questionnaires, recalling activities during 4 age epochs. We performed separate logistic regression models for physical activity measures.
Results
Compared with controls, POP cases had greater body mass index and parity. Median overall lifetime activity, expressed in metabolic equivalents-hours/week, did not differ significantly between cases and controls. In adjusted analyses, we observed no associations between odds of POP and overall lifetime physical activity, lifetime leisure activity, or lifetime strenuous activity. There was a marginally significant nonlinear relationship between teen strenuous activity and POP with an increase in the log-odds of POP for women reporting ≥21 hours/week of strenuous activity ( P = .046).
Conclusion
Lifetime physical activity does not increase the odds of anatomic POP in middle-aged women not seeking care for POP. Strenuous activity during teenage years may confer higher odds of POP. This relationship and the potential role of physical activity and POP incidence should be evaluated prospectively.
Physical activity is crucial in maintaining health, but high intensity activity increases risk for injury. Understanding how physical activity impacts pelvic organ prolapse (POP) is important: in their lifetimes, up to 1 in 5 women have surgery for POP. Childbirth, in particular vaginal delivery, increases the risk of POP, but our understanding of other potentially modifiable risk factors is limited. Prevailing expert opinion holds that chronic repetitive straining, heavy lifting and high-impact activity can eventually produce changes in muscles, ligaments and connective tissue, leading to POP. To prevent POP, the American Urogynecologic Society recommends avoiding heavy lifting and repetitive strenuous activities.
Women with POP appear more likely to report strenuous jobs than women without. However, limitations of published studies include not considering confounders, poorly defining occupational and activity histories, using nonstandardized POP outcomes, and excluding household activities, which represent a large portion of daily activity for many women. No study systematically assesses lifetime activity. Exploring the association between lifetime physical activity and POP cannot ethically be done in a randomized trial; a life-long cohort study, although possible, would be infeasible. Therefore, we conducted this case-control study to determine whether POP, defined by structured pelvic examination, is associated with (1) overall lifetime activity (leisure, outdoor, household, and occupational), (2) lifetime leisure activity, (3) lifetime strenuous activity, and (4) strenuous activity during the teen years. We analyzed strenuous activity during teen years as it is plausible that such activity, during this period of rapid changes in musculoskeletal structure, hormones, and weight, could influence pelvic floor integrity.
Materials and Methods
Institutional review boards of the University of Utah and Intermountain Healthcare approved this study. All participants completed an informed consent process. Detailed study methods have been published.
Research nurses recruited women attending 1 of 17 primary care level gynecologic and family medicine clinics located across the Salt Lake Valley. Initially, we also recruited women from community advertising (flyers, brochures) but as relatively few women responded, relied primarily on in-person recruitment.
Women were initially excluded if they were pregnant or within 6 months postpartum, <39 or >65 years, had prior surgical treatment for POP or incontinence, were not able to walk independently, had medical conditions associated with pelvic floor disorders or low physical activity (uncontrolled diabetes, neurologic disorders such as multiple sclerosis, spinal cord injury, or stroke, rheumatoid arthritis, radical hysterectomy or pelvic irradiation), had urgency-predominant incontinence, were currently undergoing treatment for cancer, or were unable to complete questionnaires. Underweight women (body mass index [BMI] <18.5 kg/m 2 ) and women in obesity class III (BMI ≥40 kg/m 2 ) were excluded as they are more likely to have functional and activity limitations. We chose the age range 39–65 years to reflect the population, included in the original validation of the physical activity instrument chosen for this study, which is likely to have developed POP and is still of an age likely to engage in a variety of physical activities. Trained research nurses performed the Pelvic Organ Prolapse Quantification (POP-Q), a reproducible method for assessing vaginal support. We defined POP as present when any segment of the vagina descended at least 1 cm below the hymen (≥+1 cm) and absent when all vaginal segments were at least 1 cm above the hymen (≤−1 cm). We did not standardize the time of POP-Q examinations, as others found no differences in POP-Q values between examinations done in the morning or afternoon. All participants voided immediately before the examination.
To assess lifetime physical activity, we used the self-administered, reliable, and valid Lifetime Physical Activity Questionnaire (LPAQ ) designed for use in women. The LPAQ assesses physical activity over 4 age periods, menarche to age 21, 22-34, 35-50, and 51-65 years, and includes leisure activity, outdoor work, and housework. The LPAQ is scored using metabolic equivalents (METs) obtained from the Compendium of Physical Activities to calculate MET hours per week. METs provide a way to standardize absolute activity intensity that reflects multiples of the resting metabolic rate ( Table 3 legend). Because the LPAQ does not query occupational activity, we added the Occupation Questionnaire (OQ), a component of the Lifetime Overall Physical Activity Questionnaire (LTPAQ).
We obtained overall lifetime physical activity by multiplying the MET score assigned to each activity by the reported number of hours per week, fraction of months in a year, and fraction of years lived in each age epoch, and added the average MET hours per week calculated on the Occupation Questionnaire. To calculate overall leisure physical activity, we restricted activities to those related to traditional exercise and recreation. Although there is much overlap between vigorous activities (defined as >6 METs ) and activities that result in higher force on the pelvic floor (which we term strenuous activity), some vigorous activities are not strenuous (like fast swimming) and some strenuous activities are not vigorous (like carrying a toddler for extended periods). We classified activities associated with relatively higher intraabdominal pressures or considered by pelvic floor experts to be potentially associated with the development or progression of POP as strenuous ( Table 1 ) and reported average weighted strenuous hours per week.
| Activity |
| Aerial dance trapeze |
| Backpacking |
| Bailing hay |
| Basketball |
| Carrying large pails of water or feed |
| Carrying loads over 30 lb |
| Cheerleading |
| Chopping wood |
| Cleaning large animal pens/farm work |
| Climbing >10 flights of stairs per day |
| European (team) handball |
| Field hockey |
| Football |
| Hangliding/windsurfing |
| Health club exercise, general |
| Heavy carpentry |
| Heavy garden work (shoveling, turning soil) |
| Heavy housecleaning |
| High jumping (track and field) |
| Jet ski |
| Jumping on trampoline |
| Jumping rope |
| Kickball |
| Kickboxing |
| Lacrosse |
| Lifting >30 lb from floor |
| Lifting >30 lb from counter height |
| Lifting heavy weights (recreational/fitness) |
| Lifting or carrying children or dependent elder |
| Martial arts (all varieties) |
| Motorcycle racing (motor cross) |
| Moving heavy furniture without assistance |
| Mowing lawn with push mower |
| Other racquet sports |
| Rock climbing |
| Rugby |
| Skiing, downhill; snowboarding |
| Snow shoveling by hand |
| Soccer |
| Softball/baseball |
| Springboard diving |
| Sprinting |
| Tennis |
| Ultimate Frisbee |
| Volleyball |
| Wallyball |
| Water skiing |
We collected self-reported information about risk factors for pelvic floor disorders ( Table 1 ). Because of the inaccuracy of recall of obstetric events, other than type of delivery, we did not ask more focused questions about childbirth history. We used the validated Epidemiology of Prolapse and Incontinence Questionnaire (EPIQ) to collect pelvic floor symptoms. Participants completed questionnaires either on a paper or an electronic survey.
Exercise science graduate students reviewed missing and improbable responses on each LPAQ and OQ with participants using an established protocol. The LPAQ+OQ was considered insufficient for analysis if: (1) no physical activity was recorded of any type for an entire age epoch, (2) no physical activity over the entire LPAQ was recorded for leisure time or household domains, (3) overall physical activity was reported for more than 168 hours per week in any age epoch, or (4) calculated physical activity exceeded 671 MET hours/week in any age epoch.
From the initial pool of participants, we then applied additional exclusion criteria. Because urinary incontinence and POP may coexist but have different risk factors, we excluded women with moderate/severe urinary incontinence defined as a score of ≥3 on the reliable, validated Incontinence Severity Index. Consistent with research by others, we excluded women with vaginal descent at the hymen to more clearly delineate POP vs no POP. Finally, we excluded those that did not return the activity questionnaires, or that returned them but their quality was insufficient for analysis.
Research nurses obtaining outcome measures were masked to LPAQ + OQ results and exercise science researchers were masked to group assignment.
The a priori calculated sample size, fully explained elsewhere, of at least 175 cases and 175 controls was calculated to provide over 80% power at the 2-sided 5% significance level to detect a protective odds ratio of 0.295 for a 1 SD increase in actual physical activity, accounting for measurement error.
Analysis
We planned a priori to frequency match controls and cases for age, BMI, and recruitment source (primary care clinics vs community advertising). However, before beginning data analysis, we elected not to frequency match or adjust for BMI, as 2 prospective cohort studies published after our study began showed that lifetime physical activity ‘causes’ BMI. Thus, BMI is on the direct pathway between lifetime activity and POP and is an effect of lifetime physical activity; adjusting could eliminate the association of activity with POP by overadjustment. We frequency matched controls to cases 1:1 by recruitment source and age (39-49, 50-60, 61-65 years), and selected controls using a computerized random number generator when >1 was eligible.
We grouped physical activity variables into quintiles based on their distribution in the selected control group. In light of recent literature highlighting the independent deleterious effect of sedentary activity, we assigned the 2nd quintile as the reference group. We performed logistic regression with variable selection guided by an updated directed acyclic graph (DAG), in which BMI was depicted as an intermediate variable, developed using DAGitty version 2.0. Required adjustment variables were education and the age match variable. Cough and constipation were also suggested, but the cell sizes for these were too small to include. We further adjusted for number of vaginal deliveries and hysterectomy status, based on past literature, which was permissible per the DAG. Regression diagnostics were checked for multicollinearity and influential observations. The primary physical activity measures were analyzed in separate models. Plots of initial regression coefficients were inspected, and the Stata multivariable fractional polynomials procedure was run to examine the functional relationship of physical activity variables with POP. Variables demonstrated a linear relationship on the logit scale, except for strenuous activity in the teen epoch, which had a cubic relationship.
Missing values were addressed in the final models using multiple imputations in SAS 9.3 (SAS Institute, Cary, NC) with fully conditional specification, predictive mean matching of continuous variables, and logistic regression prediction of categorical variables. As a sensitivity analysis, odds ratios were re-estimated using simulation-extrapolation (SIMEX), with bootstrapped standard errors to adjust for measurement error, using measurement error variances from our auxiliary reproducibility substudy, in which test-retest and intermethod (web vs paper administration) intraclass correlations were 0.64-0.88.
We used a 5% significance level for tests of effects, but considered P values for individual quintiles vs the reference category to be significant if < .01, to adjust for multiple comparisons. All statistical programming calculations were verified by a second independent research team member. Analysis was performed using SAS 9.3 (SAS Institute) and the multivariable fractional polynomial and simulation extrapolation procedures in Stata 11 and 12 (StataCorp, College Station, TX).
Results
We enrolled 1610 women; 1538 (95.5%) from primary care clinics and 72 (4.5%) from community advertising. After applying exclusion criteria demonstrated in Figure 1 , there were 251 potential cases and 889 potential controls. Of these, 969/1140 (85%) returned the study questionnaires. There were no differences in age, BMI, race, ethnicity, or case/control status between those that did or did not return questionnaires. Of those that returned study questionnaires, LPAQ + OQ quality was sufficient for analysis in 864/969 (89.2%); there were no differences in these demographics between those with sufficient or insufficient questionnaire quality. All but 1 of the 192 potential cases could be matched 1:1 with a control. Participant characteristics are summarized in Table 2 . The mean age (SD) of the population was 50.1 (7.1) years. There was a trend toward higher BMI in cases compared with controls (26.2 vs 25.2 kg/m 2 , respectively, P = .051). POP cases had greater parity (2.83 [SD 1.59] vs 1.84 [1.57] in controls, P < .0001,) and more vaginal deliveries (2.66 [1.6] vs 1.53 [1.58], P < .0001). Compared with women with 0 vaginal deliveries, those with 1, 2 and ≥3 had 3.50 (95% confidence interval [CI], 1.62–7.57), 5.64 (95% CI, 2.95–10.79), and 7.37 (95% CI, 4.02–13.53) times the odds of being POP cases. Other than the symptom of vaginal bulge, more common in the POP group (19.95% vs 4.2% in controls, P < .001), there were no differences in other pelvic floor symptoms between cases and controls, respectively, in urinary frequency (29.1% vs 26.7%, P = .60), urinary urgency (38.4% vs 30.0%, P = .08), urge urinary incontinence (23.7% vs 22.3%, P = .76), pelvic pain (12.0% vs 11.0%, P = .75), or fecal incontinence (20.4% vs 18.3%, P = .60).
| Characteristic | Control | POP case | P value | Univariate OR (95% CI) |
|---|---|---|---|---|
| Age (continuous), n, mean (SD) | 191, 50.74 (7.09) | 191, 51.31 (7.07) | NA | NA |
| Age (categorical), n (%) | NA | NA | ||
| 39-50 | 81 (42.41) a | 81 (42.41) | ||
| 50-61 | 88 (46.07) | 88 (46.07) | ||
| 61-65 | 22 (11.52) | 22 (11.52) | ||
| BMI (continuous, units = 5 for OR estimate), n, mean (SD) | 191, 25.23 (4.60) | 191, 26.17 (4.74) | .051 | 1.243 (0.999–1.545) |
| BMI (categorical), n (%) | .1288 | |||
| 18.5-25 | 112 (58.64) | 95 (49.74) | Referent | |
| 25-30 | 49 (25.65) | 52 (27.23) | 1.251 (0.777–2.015) | |
| 30-40 | 30 (15.71) | 44 (23.04) | 1.729 (1.009–2.963) | |
| Parity (continuous), n | 190 | 189 | < .0001 | 1.495 (1.299–1.722) |
| Mean (SD) | 1.84 (1.57) | 2.83 (1.59) | ||
| Median (range) | 2.00 (0.00–7.00) | 3.00 (0.00–8.00) | ||
| Parity (categorical), n (%) | < .0001 | |||
| Missing | 1 (0.52) | 2 (1.05) | ||
| 0 | 54 (28.27) | 15 (7.85) | Referent | |
| 1 | 23 (12.04) | 13 (6.81) | 2.035 (0.837–4.948) | |
| 2 | 57 (29.84) | 58 (30.37) | 3.663 (1.858–7.222) | |
| 3+ | 56 (29.32) | 103 (53.93) | 6.621 (3.429–12.787) | |
| Number of vaginal deliveries, n | 190 | 189 | < .0001 | 1.547 (1.346–1.779) |
| Mean (SD) | 1.53 (1.58) | 2.66 (1.64) | ||
| Median (range) | 1 (0–7) | 2 (0–8) | ||
| Vaginal delivery (categorical), n (%) | < .0001 | |||
| Missing | 1 (0.52) | 2 (1.05) | ||
| 0 | 76 (39.79) | 19 (9.95) | Referent | |
| 1 | 24 (12.57) | 21 (10.99) | 3.500 (1.618–7.573) | |
| 2 | 39 (20.42) | 55 (28.80) | 5.641 (2.948–10.793) | |
| 3+ | 51 (26.70) | 94 (49.21) | 7.372 (4.016–13.533) | |
| Number of cesarean deliveries, n | 189 | 189 | .0459 | 0.703 (0.497–0.994) |
| Mean (SD) | 0.31 (0.77) | 0.17 (0.49) | ||
| Median (range) | 0 (0–6) | 0 (0–3) | ||
| Cesarean delivery (categorical), n (%) | .0628 | |||
| Missing | 2 (1.05) | 2 (1.05) | ||
| 0 | 154 (80.63) | 163 (85.34) | Referent | |
| 1 | 17 (8.90) | 21 (10.99) | 1.167 (0.593–2.295) | |
| 2 | 15 (7.85) | 3 (1.57) | 0.189 (0.054–0.666) | |
| 3+ | 3 (1.57) | 2 (1.05) | 0.630 (0.104–3.821) | |
| Hispanic, n (%) | .5873 | |||
| No | 183 (95.81) | 185 (96.86) | Referent | |
| Yes | 8 (4.19) | 6 (3.14) | 0.742 (0.252–2.180) | |
| Race (OR and P value are based on nonwhite vs white), n (%) | .9909 | 0.995 (0.386–2.563) | ||
| Missing | 1 (0.52) | 0 (0.00) | ||
| American Indian | 0 (0.00) | 2 (1.05) | ||
| Asian | 8 (4.19) | 6 (3.14) | ||
| Black | 1 (0.52) | 1 (0.52) | ||
| White | 181 (94.76) | 182 (95.29) | ||
| Highest grade or year of school completed, n (%) | .0805 | |||
| Less than high school | 0 (0.00) | 1 (0.52) | NA | |
| High school | 16 (8.38) | 20 (10.47) | 1.983 (0.935–4.205) | |
| Some college/associates | 48 (25.13) | 54 (28.27) | 1.700 (0.989–2.921) | |
| Bachelors | 59 (30.89) | 71 (37.17) | 1.818 (1.091–3.031) | |
| Graduate/professional degree | 68 (35.60) | 45 (23.56) | Referent | |
| Current smoker, n (%) | .7784 | |||
| No | 184 (96.34) | 185 (96.86) | Referent | |
| Yes | 7 (3.66) | 6 (3.14) | 0.853 (0.281–2.586) | |
| Hysterectomy, n (%) | .8841 | |||
| No | 163 (85.34) | 164 (85.86) | Referent | |
| Yes | 28 (14.66) | 27 (14.14) | 0.958 (0.541–1.697) | |
| Postmenopausal, n (%) | .2189 | |||
| Missing | 2 (1.05) | 0 (0.00) | ||
| No | 103 (53.93) | 87 (45.55) | Referent | |
| Yes | 80 (41.88) | 97 (50.79) | 1.435 (0.952–2.166) | |
| Do not know | 6 (3.14) | 7 (3.66) | 1.381 (0.447–4.264) | |
| Hypertension, n (%) | .7655 | |||
| No | 164 (85.86) | 166 (86.91) | ||
| Yes | 27 (14.14) | 25 (13.09) | 0.915 (0.510–1.642) | |
| Arthritis, n (%) | .7815 | |||
| No | 161 (84.29) | 159 (83.25) | Referent | |
| Yes | 30 (15.71) | 32 (16.75) | 1.080 (0.627–1.861) | |
| Diabetes, n (%) | .4198 | |||
| No | 187 (97.91) | 189 (98.95) | Referent | |
| Yes | 4 (2.09) | 2 (1.05) | 0.495 (0.090–2.734) | |
| Cancer, n (%) | .1097 | |||
| No | 182 (95.29) | 174 (91.10) | Referent | |
| Yes | 9 (4.71) | 17 (8.90) | 1.976 (0.858–4.550) | |
| Cough, n (%) | .1383 | |||
| No | 186 (97.38) | 190 (99.48) | Referent | |
| Yes | 5 (2.62) | 1 (0.52) | 0.196 (0.023–1.692) | |
| Heart attack or angina, n (%) | NA | NA | ||
| No | 190 (99.48) | 191 (100.00) | ||
| Yes | 1 (0.52) | 0 (0.00) | ||
| Major depression, n (%) | .4819 | |||
| No | 183 (95.81) | 180 (94.24) | Referent | |
| Yes | 8 (4.19) | 11 (5.76) | 1.398 (0.550–3.556) | |
| Allergies, n (%) | .2729 | |||
| No | 125 (65.45) | 135 (70.68) | Referent | |
| Yes | 66 (34.55) | 56 (29.32) | 0.786 (0.510–1.209) | |
| Sleep apnea, n (%) | .0418 | |||
| No | 188 (98.43) | 180 (92.24) | ||
| Yes | 3 (1.57) | 11 (5.76) | 3.830 (1.051–13.952) | |
| Chronic constipation, n (%) | .6624 | |||
| No | 162 (84.82) | 165 (86.39) | ||
| Yes | 29 (15.18) | 26 (13.61) | 0.880 (0.497–1.560) | |
| Number of prescription medications–other than vitamins and hormones (continuous), n | 189 | 190 | .7601 | 1.016 (0.915–1.129) |
| Mean (SD) | 1.5 (1.74) | 1.6 (2.10) | ||
| Median (range) | 1 (0–9) | 1 (0–12) | ||
| Self-reported health status, n (%) | .5401 | |||
| Excellent | 62 (32.46) | 56 (29.32) | Referent | |
| Very good | 91 (47.64) | 97 (50.79) | 1.180 (0.744–1.871) | |
| Good | 37 (19.37) | 34 (17.80) | 1.017 (0.564–1.834) | |
| Fair | 1 (0.52) | 4 (2.09) | 4.428 (0.481–40.810) | |
| Recruitment type, n (%) | NA | |||
| Primary | 175(92.15) | 176 (92.15) | NA | |
| Community | 15 (7.85) | 15 (7.85) | NA |
Summary measures for the primary physical activity variables by group are shown in Table 3 . We observed no evidence that either lifetime overall, leisure or strenuous physical activity were associated with increased odds of POP in multivariable models ( Table 4 ). However, strenuous physical activity in the teenage years exhibited a nonlinear (cubic polynomial) relationship with the log-odds of POP ( P = .046) and was a risk factor for women reporting ≥21 hours/week of teen strenuous physical activity. Because this is a nonlinear relationship, the odds ratio is not constant and is illustrated in Figure 2 .
| Variable | Control | POP case |
|---|---|---|
| Overall lifetime activity (average MET-hours/week), n a | 191 | 191 |
| Mean (SD) | 154.64 (85.64) | 154.67 (74.31) |
| Median (IQR) | 146.38 (92.24–196.33) | 142.88 (104.23–190.69) |
| Lifetime leisure activity (average MET-hours/week), n | 191 | 191 |
| Mean (SD) | 38.77 (37.34) | 32.83 (33.90) |
| Median (IQR) | 29.27 (13.35–49.70) | 22.34 (9.87–46.40) |
| Lifetime strenuous activity (average hours/week), n | 191 | 191 |
| Mean (SD) | 9.30 (6.19) | 10.56 (7.63) |
| Median (IQR) | 7.77 (4.54–13.02) | 8.98 (5.13–14.04) |
| Lifetime moderate activity (average hours/week), n b | 191 | 191 |
| Mean (SD) | 21.63 (16.06) | 23.01 (14.16) |
| Median (IQR) | 16.97 (10.73–29.40) | 19.82 (12.41–29.96) |
| Lifetime vigorous activity (average hours/week), n b | 191 | 191 |
| Mean (SD) | 2.30 (2.82) | 1.75 (2.07) |
| Median (IQR) | 1.42 (0.52–3.10) | 1.05 (0.39–2.33) |
| Strenuous activity (average hours/week) in 1st age epoch (12-21 years), n | 191 | 191 |
| Mean (SD) | 5.08 (4.88) | 5.36 (6.21) |
| Median (IQR) | 3.30 (1.29–7.54) | 3.18 (1.42–6.57) |
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