David L. Nordstrom

Risk factors for carpal tunnel syndrome in a general population.

OBJECTIVE: To determine the individual, physical, and psychosocial risk factors for carpal tunnel syndrome in a general population. METHODS: Population based case-control study in Marshfield epidemiological study area in Wisconsin, USA. Cases were men and women aged 18-69 with newly diagnosed carpal tunnel syndrome (n = 206 (83.1%) of 248 eligible). Controls were a random sample of residents of the study area who had no history of diagnosed carpal tunnel syndrome (n = 211 (81.5%) of 259 eligible). Cases and controls were matched by age. Telephone interviews and reviews of medical records obtained height and weight, medical history, average daily hours of exposure to selected physical and organisational work factors, and self ratings on psychosocial work scales. RESULTS: In the final logistic regression model, five work and three non-work variables were associated with risk of carpal tunnel syndrome, after adjusting for age. For each one unit of increase in body mass index (kg/m2), risk increased 8% (odds ratio (OR) 1.08; 95% confidence interval (95% CI) 1.03 to 1.14). Having a previous musculoskeletal condition was positively associated with carpal tunnel syndrome (OR 2.54; 95% CI 1.03 to 6.23). People reporting the least influence at work had 2.86 times the risk (95% CI, 1.10 to 7.14) than those with the most influence at work. CONCLUSIONS: Carpal tunnel syndrome is a work related disease, although some important measures of occupational exposure, including keyboard use, were not risk factors in this general population study. The mechanism whereby a weight gain of about six pounds increases the risk of disease 8% requires explanation.

Incidence of diagnosed carpal tunnel syndrome in a general population

We sought to determine the incidence rate of carpal tunnel syndrome in the general population. Using three different case definitions, we conducted a prospective study to ascertain by medical record review all cases of incident disease in a defined population during a 2-year period. Newly diagnosed probable or definite carpal tunnel syndrome (N = 309) occurred at a rate of 3.46 cases per 1,000 person-years (95% confidence interval = 3.07-3.84). The incidence rate in our study was 3.5 times higher than the rate 20 years ago in a Minnesota city. The rate difference probably results from a combination of reasons, including a true rise in incidence.

Long-term symptom outcomes of carpal tunnel syndrome and its treatment

A retrospective follow-up study of a population-based case series was conducted to determine the clinical course and outcomes of carpal tunnel syndrome (CTS). A total of 425 cases first diagnosed between 1979 and 1988 were followed through 1993. Among patients who did not have surgery, median duration of symptoms was between 6 and 9 months, but 22% had symptoms for 8 years or longer. Patients who had surgery were about 6 times more likely to have resolution of their symptoms than were patients who did not have surgery. Patients who had surgery 3 or more years after their initial diagnosis of CTS were less than half as likely to have symptom resolution than were patients who had surgery within 3 years of diagnosis. The results indicate that surgery is a highly effective treatment, but duration of CTS prior to surgery is a key determinant of surgical outcome.

Epidemiologic research in an integrated regional medical care system: The Marshfield Epidemiologic Study Area

To capitalize on Marshfield Clinics advantages for population-based health research, we developed the Marshfield Epidemiologic Study Area (MESA). Marshfield Clinic is an integrated system consisting of a large multispecialty clinic and 23 affiliated clinics. Clinic physicians provide virtually all of the medical care, both inpatient and outpatient, for residents of the area. MESA consists of 14 ZIP codes in which over 95% of the 50,000 residents and most significant health events are captured in Marshfield Clinic databases, including all deaths, 94% of hospital discharges, and 92% of medical outpatient visits. MESA exemplifies the research potential of integrated medical care systems and the efforts required to realize that potential. Because it is representative of a defined population and provides an unselected sample of patients, MESA is well suited for epidemiologic research and research elucidating the clinical spectrum and natural history of diseases and the effectiveness of treatment.

Machine-related occupational injuries in farm residents

Farm machinery is an important contributor to the high rates of occupational injury in agriculture. As part of a population-based case-control study, we studied risk factors for machine-related farm injuries. Case patients were farm residents residing in a geographically defined area of central Wisconsin who experienced a farm injury associated with a tractor, farm implement, or other machine which required medical or chiropractic care from May 1990 through April 1992. Controls were selected from an ad hoc census of farm residents in the same area. Telephone interviews regarding demographic characteristics, safety behaviors, and farming practices were completed for 97.8% of 90 case patients and for 82.8% of 221 control subjects. Personal characteristics significantly associated with an increased risk of machine-related injury included the number of hours worked per week and working primarily as a farmer. Dairy farms, farms with nonresident workers, and large farms were associated with an increased risk of injury while farms with registered cows and farms where cows were fed in the barn even in summer experienced fewer injuries. Based on a logistic regression model, the independent risk factors for machine-related farm injury included hours worked per week (2% increased risk/nonresident workers on farm (odds ratio) (OR) = 2.32; 95% confidence interval (CI): 1.07 to 5.06), cows fed in barn in summer (OR = 0.28; 95% CI: 0.12 to 0.64), and registered cows on farm (OR = 0.36; 95% CI: 0.17 to 0.79). Farm safety practices did not appreciably influence the risk of machine-related farm injury.

A population based case-control study of agricultural injuries in children.

OBJECTIVES: To identify preventable risk factors related to agricultural injuries occurring to children on family farms. SETTING: A geographically defined central region of Wisconsin, USA with nearly 1800 family dairy farms. METHODS: A two year, population based incidence study of occupational injuries among farm residents was conducted. For cases, trained staff abstracted information on the nature, severity, and treatment of the injury from the patients medical record. Staff also administered a telephone questionnaire to cases and controls, usually answered by parents. RESULTS: There were 60 cases of farm residents younger than 18 years who sought care for acute agriculture related injuries. Farms on which uninjured children lived served as controls (n = 102). Multivariate analyses of 16 different variables revealed three significantly related to injuries to children: hours worked per week (odds ratio (OR) = 1.05; 95% confidence interval (CI) = 1.01 to 1.08); presence of disabled safety device (OR = 2.64; 95% CI = 1.10 to 6.35); and feeding cows by grazing (OR = 0.22; 95% CI = 0.06 to 8.83). CONCLUSIONS: Interventions designed to reduce the risk of agricultural injuries to farm children should acknowledge the participation of children as productive workers on the farm. Although education has been the standard method for encouraging safe practices in farm work, additional approaches, such as limiting the number of hours a child works, avoiding the disabling of safety devices, and using specific methods of managing cows, should also be adopted to minimize injury risks to farm children.

Fall‐related occupational injuries on farms

We assessed risk factors for fall-related farm injuries in a population-based, case-control study. Cases had to reside in a defined geographic region served by a single medical center. Multiple sources reported cases, and a special farm census enabled random selection of controls, The annual risk of farm fall injury was 7.5 (95% CI: 5.7, 10.0) per 1,000 person-years. The crude incidence rate was higher in men, while the rate based on hours of farmwork was higher in women. In a multivariate analysis of risk factors, three factors were significantly associated with the risk. The risk of fall injury increased 2% (95% CI: 1%, 4%) per hour worked. Residents of farms with some farm workers not living on the farm had a fall injury rate 2.5 (95% CI: 1.0, 6.2) times greater than residents of other farms. Residents of farms with registered cows had one-third (95% CI: 0.14, 0.93) the risk of residents of other farms. To identify environmental hazards for fall injuries, researchers from several disciplines may need to collaborate in the design and conduct of studies that include injury site investigations.

Animal-related Occupational Injuries in Farm Residents

Animal-related injuries are an unusual hazard of farming that have received little study.We studied risk factors for animal-related injury as part of a population-based, case-control study of agricultural injuries. Cases were farm residents living in a geographically defined area of central Wisconsin who had injuries associated with farm animals from May 1990 to April 1992 which required medical or chiropractic care. Controls were selected at random from a special census of farm residents in the area. Telephone interviews regarding demographic characteristics, farming practices, and safety behaviors were completed for 70 of 71 cases (98.6%) and 183 of 221 potential controls (82.8%). Based on a multivariable logistic regression model, the only statistically significant risk factor for animal-related farm injury was the number of hours worked per week (3% increased risk per hour). Several farm characteristics were linked with animal-related injury, but the associated 95% confidence limits included 1.0: non-resident workers on the farm (OR=2.20; 95% C.I.: 0.93-5.21), use of all-terrain vehicles for chores (OR=0.47; 95% C.I.: 0.22- 1.04), and feeding cows in the barn in summer (OR=0.39; 95% C.I.: 0.15-1.00). Future studies of animal-related farm injury should obtain more specific information on animal husbandry practices.

Rural population survey of behavioral and demographic risk factors for loaded firearms

Objectives—In the United States, firearm deaths are almost as frequent as motor vehicle deaths. Firearm unintentional and suicide death rates are raised in rural areas. This study examines firearm prevalence and storage practices in three different types of rural households. Methods—Adults from a stratified random sample of 983 households in a rural Iowa county were interviewed. The χ2 test of independence was used to assess association between loaded, unlocked firearms and seven behavioral and demographic risk factors. Results—Nearly 67% of respondents reported firearms in their households. Nearly 7% of households had a loaded, unlocked gun. Prevalence of firearms at home was higher while prevalence of loaded, unlocked guns was lower than reported in other surveys. Prevalence of loaded, unlocked guns in farm households, 10.5%, was about twice the level in town households, 5.5% (χ2 test, p=0.033). Having taken a gun safety course was associated with more than double the prevalence of a loaded, unlocked gun, 13.5% v 5.1% (χ2 test, p=0.001). The prevalence of loaded, unlocked guns in households with a handgun, 19.3%, was four and one half times higher than in households with a long gun only, 4.2% (χ2 test, p=0.001). Households with someone with a lifetime prevalence of alcohol abuse or dependence were about twice as likely as other households, 13.0% v 6.6% (χ2 test, p=0.004), to report having loaded, unlocked firearms. Conclusions—Anyone interested in promoting safe storage of firearms in rural homes should consider these observations.

Risk factors for injury in rural Iowa: Round one of the Keokuk County Rural Health Study

BACKGROUND Unintentional injuries represent a major cause of morbidity and mortality in rural communities. This study aimed to determine the distribution of injury risk factors in a rural Iowa community and to identify the rural subgroups at highest risk for injury. METHODS We reported on 1583 participants, aged > or =25 years, from Round One of the Keokuk County Rural Health Study, a longitudinal panel study of a rural community. The self-reported data were collected during face-to-face interviews. RESULTS Our data suggested that several risk factors for injury are not uniformly distributed among rural populations. Male farmers were significantly less likely to wear their seatbelts than townspeople or rural nonfarmers. However, farm women were as likely to wear seatbelts as other women. Both male and female farmers were more likely to use all-terrain vehicles than townspeople or rural nonfarmers. In contrast, townspeople were more likely to ride bicycles than either farmers or rural nonfarmers. Townspeople were less likely to have firearms in their homes than either farmers or rural nonfarmers. Farmers were most likely to have fired a gun in the last year. Male farmers aged <65 years were less than half as likely as other men the same age to report a history of alcohol abuse. Binge drinking was equally frequent among farmers, rural nonfarmers, and townspeople. CONCLUSIONS These differences in risk behavior in a rural county suggest the possibility of targeting specific rural injury prevention interventions at those with the highest risk for dangerous behavior.