Back Pain Among Persons Working on Small or Family Farms -- Eight Colorado Counties, 1993-1996

In the United States, work-related back pain often results in lost wages, reduced productivity, and increased medical costs (1,2). However, national surveillance data about these injuries, such as occupationally acquired back pain among workers on small or family farms, are limited (3). To characterize back pain in a farming population, researchers at Colorado State University interviewed adult farmers residing in eight northeastern Colorado counties (Larimer, Logan, Morgan, Phillips, Sedgewick, Washington, Weld, and Yuma) during 1993-1996, using the Colorado Farm Family Health and Hazard Survey (CFFHHS). This report summarizes the findings of CFFHHS, which indicate that back pain is common among farmers and most frequently attributed to repeated activities (RAs) (e.g. lifting, pushing, pulling, bending, twisting, and reaching).

University researchers selected a sample of 500 small or family farms (i.e., less than or equal to 10 workers) in proportion to the number of Colorado farms in the National Agricultural Statistical Reporting Districts for Crop and Livestock. During the 3-year period using the CFFHHS questionnaire, 759 adults (aged greater than or equal to 18 years) were interviewed from 458 (92%) farms to determine whether the respondents had experienced daily back pain for greater than or equal to 1 week during the 12 months preceding the interviews. The p values for comparison of back pain prevalence by sex were calculated using the chi-square test. Most (458 {60%}) respondents were men. Average age of respondents was 50.5 years (range: 24-85 years).

Of the 458 men surveyed, 411 (90%) worked on farms greater than or equal to 5 days per week; 451 (99%) worked greater than or equal to 2 days per week. Of the 301 women surveyed, 136 (46%) reported working on farms greater than or equal to 5 days per week; 227 (66%) worked greater than or equal to 2 days per week. During the 12 months preceding the interviews, 196 (26%) respondents experienced back pain lasting greater than or equal to 1 week. The prevalence of back pain among men was slightly higher than among women; both sexes reported that the lower back was the area most often affected (Table_1). Approximately 45% of respondents attributed back pain to RAs; however, 13% of men and 8% of women attributed back pain to single incidents (SIs) such as slipping or falling (Table_1). Approximately one fifth of all respondents attributed back pain to both RAs and SIs. Depression, occupation, and long-term employment in agriculture also had statistically significant associations with back pain (4). In all age categories, the prevalence of back pain did not differ significantly among men and women, except among those aged 30-39 years (36% versus 21%, respectively; p=0.044).

For men, work-related RAs were more likely than nonwork-related RAs to cause back pain; for women, nonwork-related RAs were more likely to cause back pain. Compared with women, men experienced back pain more often at work than at other locations, but this difference was statistically significant only for RA-related back pain. The overall prevalence of RA-related back pain among women was slightly greater among those who performed farm work than those whose duties were restricted to work in the home, but this difference was not statistically significant. Because of back pain, 38% of men and 30% of women had made "major" changes (undefined in the survey) in work activities; 10% and 8%, respectively, either changed or stopped their work permanently (Table_1).

Dairy farmers were substantially more likely to report back pain (43%) than farmers who produced field crops (27%; p=0.058) or raised livestock (25%; p=0.054). The prevalence of back pain among farmers working on large farms (i.e., annual sales greater than or equal to $100,000) was slightly higher than that of those working on small farms (29% versus 24%, respectively; p=0.15).

Reported by: H Xiang, MD, L Stallones, PhD, S Hariri, MS, A Darragh, MS, Y Chiu, MS, J Gibbs-Long, Colorado Injury Control Research Center, Dept of Environmental Health, Colorado State Univ, Fort Collins. Surveillance Br, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note: Many risk factors for occupational and nonoccupational back pain have been proposed (5), with general agreement that overexertion and chronic whole-body vibration are important risk factors for work-related back pain (6). CFFHHS confirmed that back pain is a major health problem among farmers in eight Colorado counties working on small or family farms.

Surveillance information about injuries among small and family farmers might be inadequately represented in national data. Two national data sources are available to estimate the prevalence and characteristics of work-related back pain in the United States: the Bureau of Labor Statistics (BLS) Annual Survey and the 1988 Occupational Health Supplement (OHS) in the National Health Interview Survey (NHIS). The BLS Annual Survey is based on sampled employers' reporting on occupational injuries and illnesses. In 1996 (the most recent year for which data are available), incidence of nonfatal injury or illness affecting the back and involving lost work days was 75.1 (0.8%) per 10,000 full-time agricultural workers (7): 1.1% among dairy farmers, 1.0% among workers in livestock production, and 0.7% among workers in crop production. BLS data excluded self-employed farmers and farms with less than 11 employees.

The OHS samples U.S. civilian noninstitutionalized adults aged greater than or equal to 18 years (8). Although farm size was not considered in NHIS sampling, OHS data excluded people who "only worked around the house"; in comparison, CFFHHS did not exclude small farms or homemakers. In 1988, OHS/NHIS (9) included questions about back pain during the 12 months preceding the interviews among adult respondents who had worked during that time (8). During 1988, the national prevalence of back pain (defined as lasting greater than or equal to 1 week, excluding menstrual back pain) was 17.6% (22.4 million cases; 149 million lost work days) (9). Among major * occupation categories for men, "farmers except horticultural" ranked fifth in the prevalence of back pain attributed to work-related activities, with 213,000 cases. Women farmers ranked 20th among major occupations, with 21,000 cases.

Data from CFFHHS revealed aspects of back pain that are not readily available in national data. CFFHHS indicated that back pain among men was associated closely with work. Among women farmers, daily domestic activities (e.g., cleaning house and caring for children) may be risk factors for back pain.

CFFHHS results have at least four limitations. First, on small farms, it may be difficult to distinguish between work-related and domestic activities. Second, the survey covered only a section of Colorado, which may have unique regional and farming characteristics; therefore, the findings may not be generalizable to other regions, states, or the rest of the country. Third, responses to the survey were self-reported and may be subject to recall biases. Finally, 27% (108) of the eligible women within a responding family unit did not participate in the survey.

The Colorado survey results verify that back pain is a major work-related health issue. The survey also suggests that regional and state-based surveillance for work-related disorders could supplement the national surveillance system for a population underestimated or excluded. Findings from the Colorado survey pointed to an area that warrants further investigations. Other states, such as California, Iowa, Kentucky, and New York, have conducted similar surveys under the FFHHS program, and their findings may provide insight about back pain among small and family farmers.

References

1. Deyo RA, Cherkin D, Conrad D, et al. Cost controversy, crisis: low back pain and the health of the public. Ann Rev Public Health 1991;12:141-56.

2. Sherelud R. Epidemiology of occupational low back pain. In: Malanga GA, ed. State of the art reviews -- occupational medicine: low back pain. Philadelphia, Pennsylvania: Hanley & Belfus, Inc, 1998:1-22.

3. Bobick TG, Myers JR. Back injuries in agriculture: occupations affected. In: McDuffie H, ed. Agricultural health and safety: workplace, environment, sustainability. New York, New York: CRC Press Inc, 1995:325-32.

4. Xiang H, Stallones L, Keefe TJ. Back pain and agricultural work among farmers: an analysis of the Colorado Farm Family Health and Hazard Surveillance survey. Am J Ind Med 1999;35: 213-22.

5. Dempsey PG, Burdorf A, Webster BS. The influence of personal variables on work-related low back disorders and implications for future research. J Occup Environ Med 1997;39:748-59.

6. Bernard BP. Low-back musculoskeletal disorders: evidence for work-relatedness. In: Bernard BP, ed. Musculoskeletal disorders and workplace factors: a critical review of epidemiological evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. Cincinnati, Ohio: US Department of Health and Human Services, Public Health Service, CDC, 1997 DHHS publication no. (NIOSH)97-141.

7. Bureau of Labor Statistics, US Department of Labor. Incidence rates for nonfatal occupational injuries and illnesses. Available at . Accessed April 19, 1999.

8. Guo HR, Tanaka S, Cameron LL, et al. Back pain among workers in the United States: national estimates and workers at high risk. Am J Ind Med 1995;28:591-602.

9. CDC. Vital and health statistics: health conditions among the currently employed: United States, 1988. Washington, DC: US Department of Health and Human Services, Public Health Service, CDC, National Center for Health Statistics, 1993 (series 10, no. 186).

For this analysis, a "major" occupation was defined as an occupation constituting greater than 0.5% of the total sex-specific working population (9).

TABLE 1. Sex-specific prevalence of back pain among farmers during the 12 months preceding interviews, by selected
characteristics -- eight Colorado counties,* 1993-1996+
======================================================================================================================
                                                  Men (n=458)                      Women (n=301)
                                         -----------------------------     ------------------------------
Characteristic                           No.      (%)      (95% CI&)        No.     (%)       (95% CI)      p value
--------------------------------------------------------------------------------------------------------------------
Part of the back affected
 Upper                                   16     (12.3)   ( 7.2%-18.5%)       9    (13.6)    ( 6.5%-22.8%)    0.375
 Middle                                  11     ( 8.5)   ( 4.3%-13.9%)       9    (13.6)    ( 6.5%-22.8%)
 Lower                                   98     (75.4)   (67.7%-82.4%)      43    (65.2)    (53.4%-76.1%)
 Not reported                             5     ( 3.8)   ( 1.2%- 7.8%)       5    ( 7.6)    ( 2.5%-15.2%)
Cause of back pain
 Single incident (SI)@                   17     (13.0)   ( 7.8%-19.3%)       5    ( 7.6)    ( 2.5%-15.2%)    0.529
 Repeated activities (RA)**              59     (45.4)   (37.0%-54.0%)      29    (43.9)    (32.2%-55.9%)
 Both SI and RA                          27     (20.8)   (14.3%-28.2%)      13    (19.7)    (11.1%-30.1%)
 Other                                   20     (15.4)   ( 9.7%-22.1%)      18    (27.3)    (17.3%-38.6%)
 Unknown                                  7     ( 5.4)   ( 2.2%- 9.9%)       1    ( 1.5)    ( 0.0%- 5.8%)
Back pain resulted from
 Work                                    13     (76.5)   (54.2%-93.0%)       2    (40.0)    ( 6.0%-81.3%)    0.133
 Home or recreation site                  4     (23.5)   ( 7.0%-45.8%)       3    (60.0)    (18.8%-94.1%)
Back pain occurred at
 Work                                    54     (91.5)   (83.1%-97.2%)      11    (37.9)    (21.4%-56.0%)    0.001
 Home or recreation site                  5     ( 8.5)   ( 2.8%-16.9%)      18    (62.1)    (44.0%-78.6%)
No. days per week worked on farm<B^++
   0                                                                         6    ( 8.6)    ( 1.3%-21.3%)    0.872
 1-4                                                                        10    (11.0)    ( 2.4%-24.7%)
 5-7                                                                        13    ( 9.6)    ( 1.8%-22.8%)
Major changes in work activities         49     (37.7)   (29.6%-46.2%)      20    (30.3)    (19.9%-41.9%)    0.306
 because of back pain
Previous job stopped or changed          13     (10.0)   ( 5.5%-15.7%)       5    ( 7.6)    ( 2.5%-15.2%)    0.579
 because of back pain

Total&&                                  130    (28.4)   (24.4%-32.6%)      66    (22.9)    (18.3%-27.8%)    0.052
--------------------------------------------------------------------------------------------------------------------
*  Larimer, Logan, Morgan, Phillips, Sedgewick, Washington, Weld, and Yuma.
+  n= 759.
&  Confidence  interval.
@  For example, slipping or falling.
** For example, lifting, pushing, pulling, bending, twisting, or reaching.
++ Women respondents only.
&& Total number reporting back pain.
======================================================================================================================

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