Osteoporosis is a systemic skeletal disorder, characterized by reduction of bone mass, deterioration of bone structure, increasing bone fragility, and increasing fracture risk 1234. It is more frequent among women than among men 56. The development of low bone mass is typically asymptomatic, with many women reporting clinical manifestations including acute back pain, limited back mobility, fragility fractures (hip, vertebrae, proximal femur, distal radius, humerus, tibia), compression of midthoracic vertebrae and upper lumbar vertebrae, progressive deformation of the spinal column (cyphosis), reduced height, and radiculopathies 245689.

Several risk factors for osteoporosis have been identified, these include female sex; Caucasian or Asiatic race; advancing age; family history of osteoporosis or fragility fractures; a low body mass index; menopause before age 45 years; prolonged amenorrhea unrelated to menopause; nulliparity; prolonged lactation; diet low in calcium and vitamin D; poor intestinal absorption of calcium; lactose intolerance; excessive caffeine or alcohol consumption; smoking; sedentary lifestyle; and prolonged treatment with thyroid hormones, glucocorticoids (e.g. cortisone), anticonvulsants, aluminum antiacids, and use of anticoagulants 134568.

Approximately 20% of bone mass is genetically determined; however, the risk of osteoporosis can be reduced by optimizing bone mass increasing during youth, conserving bone mass during adulthood, and minimizing bone mass loss during advancing age 567. Among most important preventive habits are a) weight-bearing exercise (e.g. going up and down stairs, jogging, aerobics, swimming, and isometrics; at least 30 minutes daily), b) diet or supplements containing adequate levels of calcium and vitamin D, and c) absence or cessation of smoking and no greater than moderate alcohol and/or caffeine consumption 5678910.

A study on US women aged over 25 years found that knowledge about osteoporosis was limited, irrespective of age 11. Calcium intake was sufficient in most cases, but the amount and type of physical activity was inadequate to achieve enhanced bone mass; most women in this study performed some physical activity in the course of paid work or housework, but did not admit to systematic daily exercise. Other study on Caucasian and African-American women found that most of them had heard about osteoporosis, but few women got both adequate exercise and the recommended intake of calcium per day 12. Asian women in Australia also had lower calcium intake (< 800 mg/day) and their knowledge about osteoporosis was limited 13.

There have been three related studies reported in Hispanic women: a study performed in Mexico 14, and two studies on women of Hispanic origin in the US 1516. The Mexican study considered women aged 50 – 59 years, and focused on knowledge about menopause and risk associated with premature menopause. About 90% of subjects were aware of the relationship between menopause and osteoporosis, but most subjects had little knowledge of other risk factors, and incorporated life habits that clearly increased osteoporosis risk. The studies on women of Hispanic origin in the US have yielded somewhat contradictory results. The first of these found that more than 37% of women had adequate preventive habits including the taking of calcium supplements and the performance of regular exercise; much of this was attributed to prior health education, knowledge about osteoporosis, bone-mass evaluation offered by healthcare services, and medical advice 15. The second study considered both Hispanic and African-American women, and found that most women in both groups had a poor knowledge of behaviors that promote and maintain bone mass 16. Notably, less than 50% of women performed regular physical exercise, and less than 10% had adequate calcium intake.

At present, the Salvadorean Public Health and Social Assistance Ministry does not maintain a specific record of this disease in adults, and most cases are likely classified as dorsalgy, that includes several musculoskeletal diseases such as radiculopathies, cervicalgy, lumbalgy, sciatica, spinal derived pain, and unspecified back pain 17. This reflects the fact that osteoporosis may be reported as dorsalgy. According to this report from El Salvador, in 2001 dorsalgy was the seventh most frequent cause of morbidity in women aged 50 – 59 years attending outpatient clinics, with an incidence of 3,983 new cases per 100,000 inhabitants and a total of 8,989 consultations (first-time or subsequent); in women aged 60 years or more, there were 9,754 consultations for dorsalgy in 2001.

Bearing in mind the lack of reliable epidemiological data, the present study wished to investigate osteoporosis-related life habits (including exercise and calcium intake) and knowledge about osteoporosis among Salvadorean women aged ≥ 25 years. We investigated possible relationships of these variables with age, educational level, household income, family history of osteoporosis, menopause before age 45 years, fecundity (children per woman), lactose intolerance, caffeine consumption, low in calcium diet, and use of aluminum antiacids.

The total scores regarding nine knowledge osteoporosis dimensions were similar in all age groups of interviewed women (range of median 14 – 17, average 12.1 – 14.8) out of a possible 42 points. A similar study found Taiwanese women got a mean score of 15 out of 44 points related to six osteoporosis knowledge dimensions 21, whereas surveyed American women of three age groups got averaged knowledge scores from 32 to 44 points out of 183 11. In all cited cases, the obtained scores indicate that knowledge about osteoporosis is poor or limited among surveyed subjects so health educational programs and health services regarding osteoporosis are necessary for Salvadorean women, as it is also suggested for Taiwanese 21 and American women 11 of all ages.

The present results also indicate that Salvadorean women with secondary or higher education have significantly better knowledge of osteoporosis than women with a low educational level, regardless of age. Similarly, other study found that better educated Chinese women in Singapore seem to know more about osteoporosis than those ones worst educated 22. A previous study has likewise found that osteoporosis-related knowledge is independent of age 11. Our multivariate analyses indicated that the most effective predictors of osteoporosis-related knowledge were educational level, household income, and early menopause. This latter factor perhaps affects osteoporosis-related knowledge through to give brochures and magazines to women at shopping centers, supermarkets, physician's clinics, schools, and colleges by non governmental organizations such as Salvadorean Demographical Association, dairy good producers such as New Zealand Dairy Board and Australian Milk Products, and some pharmaceutical laboratories, especially those produce calcium supplements. As well as information presented on television and in the press.

Besides, short counselling sessions about preventive aspects of osteoporosis are given by some physician's private clinics, because there is not a settled public health education program about osteoporosis in El Salvador. This country is not only case in Latin America, since Mexican women got more osteoporosis information from mass communication media than health education activities of public institutions 14. However, total knowledge about osteoporosis may not lead to an improvement in health lifestyle; it is necessary to know more about some specific aspects as osteoporosis risk factors and to acquire healthy habits to reduce the risk for low bone mass. In multivariate analyses, knowledge about osteoporosis was not a significant predictor of either amount of physical activity or total calcium intake. Previous studies likewise found that knowledge of osteoporosis does not correlate with risk-reducing life habits 1112. These authors suggested that osteoporosis-related knowledge among women of their sample was limited, the information was not fully understood or poorly internalized. They also suggested that it is unlikely that this type of knowledge will provide a basis for decisions about life style or unhealthy habits 11. These comments are perhaps similarly applicable to the subjects in our study. Other previous studies have obtained results consistent with this view that osteoporosis-related knowledge is often poorly integrated and internalized, and does not lead to improved health behaviours 12162324.

Our data on physical activity in the three age groups indicate that the amount of physical activity engaged in paid work currently declines with increasing age, whereas the amount of physical activity during housework appears to increase with increasing age. This trend was confirmed by multivariate analysis, which indicates that the most effective predictors of amount of physical activity at worksite or at home were age and educational level. Educational level attained likely increases the likelihood of obtaining paid work. However, recreational activities and other health-preventive behaviours such as to do isometric exercises may also determine total physical activity.

Considering all subjects together, most reported physical activity (96%) was performed in the course of daily housework, walking to work or shops, or standing at work or at home; only 4% was directly applicable to weight-bearing exercise. About 50% of women in the youngest age group did more than 2 hours of physical activity per week, but the amount of physical activity in the older women was markedly lower, and even in the youngest age group very few women performed the recommended daily minimum of 30 minutes of exercise per day 56. Similar results were obtained in a previous study, which found that fewer than 50% of African-American and Hispanic women interviewed in the US do 60 minutes of physical exercise per week 16.

Very few of the women interviewed for the present study employ any of the weight-bearing physical activities that are known to be especially effective for increasing bone mass and thus perhaps reducing the risk of osteoporosis, such as isometrics 25. Similar findings have been obtained in studies of Caucasian women in the US 1112 and of African-American and Hispanic women residing in the US 1216.

Independent of age and income, most women interviewed (50 – 75%) have a daily calcium intake of less than 60% of the recommended level, thus increasing the risk of osteoporosis. Similarly, in another studies of Caucasian and African-American and Hispanic women in the US 1216, and Asian and Caucasian women in Australia 13, most of these women did not fulfil the suggested calcium intake. By contrast, in other recent study of Caucasian women in the US 11, only about 20% of women ingested less than 60% of the recommended daily calcium.

The difference between our results in El Salvador and those obtained in the study of Caucasian women in the US 11 may, at least in part, reflect differences in standard of living between these two countries. Specifically, the generally higher incomes in the US may be associated with healthier diet, higher educational level, better access to healthcare, and better public education about general health and the prevention of diseases like osteoporosis. Additionally, calcium fortified foods are more readily available in the US.

The average proportion of calcium intake as dairy products was 57% in women below the poverty line and 68% in women above the poverty line; both values are close to those reported for Caucasian women in the US 11. These authors did not detect any significant variation with income, but note that their sample was smaller (n = 75) and more homogeneous (in terms of educational level and household income) than the sample of our study. The relationships between household income and calcium intake observed in our multivariate analyses likewise indicate that calcium intake varies with income. The other important predictor of calcium intake in this analysis was lactose intolerance, reported by 19% of the women interviewed; dairy calcium intake was likely lower in these women. As lightly lower prevalence of lactose intolerance (16%) was reported in the study of Caucasian women in the US 11.

The consumption of caffeine-containing drinks, especially coffee, has been shown to influence calcium intake, since these beverages often replace milk and milk-based beverages due to dairy products are relatively expensive in El Salvador and many Salvadorean families (42.9%) have a low purchasing power, and live below the poverty line 26. Excessive caffeine ingestion is also reported to accelerate bone resorption 56, and prevents intestinal calcium absorption 9.

Calcium intake also varied with age, being significantly less among younger women. Similarly, most of interviewed Caucasian and African-American young adult women in the US did not get recommended calcium intake per day 12. This may be because younger women tend to perceive dairy products as having a high content in animal fats, and thus tend to reject them, as it has been suggested by previous authors 19. Auld et al. also suggested that Hispanic women (particularly adolescents and young women) in general tend to reject dairy products more than Anglosaxon and Asiatic women.

The key practical implications of this study relate to suggest set up of primary healthcare programs regarding osteoporosis for Salvadorean women as it has also suggested for Taiwanese women 21, and Hispanic and African-American women 16, as well as training of healthcare professionals, which in light of the present study need to pay special attention to the following aspects of osteoporosis prevention:

a) The type and frequency of physical exercise.

b) Diet-related risk factors, including inadequate intake of calcium, vitamin D, and phosphorus; also the adverse effects of drinking coffee or other low-calcium drinks instead of milk or milk-based drinks.

c) The importance of monitoring menstruation frequency, since normal circulating estrogen levels and normal menstrual cycles are important for maintaining normal bone metabolism.

In addition, it is clearly important to set up health education programs to focus on integration and internalization of knowledge about osteoporosis.

Although our results indicate that many women have modest knowledge about osteoporosis concerning risk factors and preventive behaviours, this knowledge often does not translate to appropriate changes in healthy life habits as it is shown through a weak association between total osteoporosis scores and exercise or calcium intake, so that osteoporosis knowledge is not well internalized among interviewed Salvadorean women. The lack of time to practice most adequate osteoporosis preventive exercise may accounts for the weak association between foregoing variables since majority of interviewed women perform WBPA (> 8 hours/day), but as labour activities or housework. The low calcium intake among subjects may be explained through they have a low purchasing power and do not have the habit to ingest enough dairy products, the main diet calcium source 9. Non-dairy calcium intake including supplements was also low (< 370 mg/day), so that they did not fulfil the recommended daily calcium intake from this source either.

Finally, we would suggest that osteoporosis education campaigns should be directed at families as well as individuals, with the aim of fomenting within-family education of children about the importance of calcium in the diet, whether as dairy products or in other calcium-rich products such soya milk and oat-based drinks and desserts.

It showed that Salvadorean women with secondary or higher education have significantly better knowledge about osteoporosis than women with lower educational level, regardless of age. However, this knowledge does not appear to lead to improved life style or preventive habits of osteoporosis.

The amount of weight bearing physical activity (mainly walking or standing) during paid work or housework was high in the three age groups of interviewed women (over 8 hours/day). However, very few of the women interviewed for this study did not perform any of the weight-bearing physical activities that are known to be especially effective for increasing bone mass and thus reducing the risk of osteoporosis, such as going up and down stairs, jogging, aerobics, swimming, and isometrics.

Most Salvadorean interviewed women have a daily calcium intake of 60% or less than the recommended level depending of lactose intolerance, household income, age, and coffee consumption. The former variables directly affect both calcium source diversity and intake frequency. Age would influence dairy calcium intake, since younger women tend to perceive dairy products as having a high animal fat content, and thus reject them. The coffee consumption would affect calcium intake, since this beverage often replace milk. Therefore, all these factors together may be increasing the risk to develop osteoporosis among Salvadorean women.

WBPA: Weight-bearing physical activity

ANOVA: Analysis of Variance

SEM: Standard error of mean

None declared.

RHR performed the design of the study, coordinated the study, performed data analysis, and drafted the paper. SMG participed in the design of the study and provided input into the paper.