Serum parathyroid hormone is associated with increased cortical porosity of the inner transitional zone at the proximal femur in postmenopausal women: the Tromsø Study.

Serum parathyroid hormone (PTH) was associated with increased bone turnover markers and cortical porosity of the inner transitional zone at the proximal femur. These results suggest that PTH through increased intracortical bone turnover leads to trabecularisation of inner cortical bone in postmenopausal women. INTRODUCTION: Vitamin D deficiency leads to secondary hyperparathyroidism and increased risk for fractures, whereas its association with cortical porosity is less clear. We tested (i) whether serum 25-hydroxyvitamin D (25(OH)D) and PTH were associated with cortical porosity and (ii) whether the associations of 25(OH)D) and PTH with fracture risk are dependent on cortical porosity. METHODS: This case-control study included 211 postmenopausal women, 54-94 years old, with prevalent fractures and 232 controls from the Tromsø Study. Serum 25(OH)D, PTH, and bone turnover markers (procollagen type I N-terminal propeptide [PINP] and C-terminal cross-linking telopeptide of type I collagen [CTX]) were measured. Femoral subtrochanteric cortical and trabecular parameters were quantified using computed tomography, and femoral neck areal bone mineral density (FN aBMD) was quantified using dual-energy X-ray absorptiometry. RESULTS: Compared with controls, fracture cases exhibited reduced serum 25(OH)D and increased PTH, PINP, and CTX, increased femoral subtrochanteric cortical porosity, and reduced cortical thickness and FN aBMD (all, p < 0.05). Serum 25(OH)D was not associated with cortical parameters (all, p > 0.10). PTH was associated with increased PINP, CTX, and cortical porosity of the inner transitional zone and reduced trabecular bone volume/tissue volume and FN aBMD (p ranging from 0.003 to 0.054). Decreasing 25(OH)D and increasing PTH were associated with increased odds for fractures, independent of age, height, weight, calcium supplementation, serum calcium, cortical porosity, and thickness. CONCLUSIONS: These data suggest that serum PTH, not 25(OH)D, is associated with increased intracortical bone turnover resulting in trabecularisation of the inner cortical bone; nevertheless, decreasing 25(OH)D) and increasing PTH are associated with fracture risk, independent of cortical porosity and thickness.

Large Individual Differences in Serum 25-Hydroxyvitamin D Response to Vitamin D Supplementation: Effects of Genetic Factors, Body Mass Index, and Baseline Concentration. Results from a Randomized Controlled Trial.

The main aim of the study was to determine the influence of genetic factors on the serum 25-hydroxyvitamin D response to vitamin D supplementation. The main outcome measure was an increase in serum 25-hydroxyvitamin D after vitamin D supplementation. The patients are part of a randomized controlled trial in individuals with prediabetes assigned to 20 000 IU of vitamin D3 per week or placebo for 12 months. A total of 484 subjects were included in the analyses and genotyped for single nucleotide polymorphisms in the DBP, DHCR7, CYP2R1, and CYP24A1 genes. Single nucleotide polymorphisms from all 4 selected genes were significantly related to baseline serum 25-hydroxyvitamin D concentrations with differences between major and minor homozygote genotypes ranging from 4.4 to 19.2 nmol/l. In the subjects given vitamin D, those with genotypes with the highest baseline 25-hydroxyvitamin D concentration also had the highest 25-hydroxyvitamin D concentration after 12 months, and the increase (delta) in 25-hydroxyvitamin D was significantly related to 3 of the single nucleotide polymorphisms. The increase in serum 25-hydroxyvitamin D was also higher in lean vs. obese subjects, and higher in those with low baseline 25-hydroxyvitamin D concentrations. When combining these 3 factors in a linear regression model, the predicted (and observed) difference in 25-hydroxyvitamin D increase between high and low responders to the supplementation was approximately 60 nmol/l. In conclusion, due to genetic, body mass, and baseline 25-hydroxyvitamin D differences, there are huge individual variations in the serum 25-hydroxyvitamin D response to vitamin D supplementation that could be of clinical importance.

Measurement of cortical porosity of the proximal femur improves identification of women with nonvertebral fragility fractures.

UNLABELLED: We tested whether cortical porosity of the proximal femur measured using StrAx1.0 software provides additional information to areal bone mineral density (aBMD) or Fracture Risk Assessment Tool (FRAX) in differentiating women with and without fracture. Porosity was associated with fracture independent of aBMD and FRAX and identified additional women with fractures than by osteoporosis or FRAX thresholds. INTRODUCTION: Neither aBMD nor the FRAX captures cortical porosity, a major determinant of bone strength. We therefore tested whether combining porosity with aBMD or FRAX improves identification of women with fractures. METHODS: We quantified femoral neck (FN) aBMD using dual-energy X-ray absorptiometry, FRAX score, and femoral subtrochanteric cortical porosity using StrAx1.0 software in 211 postmenopausal women aged 54-94 years with nonvertebral fractures and 232 controls in Tromsø, Norway. Odds ratios (ORs) were calculated using logistic regression analysis. RESULTS: Women with fractures had lower FN aBMD, higher FRAX score, and higher cortical porosity than controls (all p < 0.001). Each standard deviation higher porosity was associated with fracture independent of FN aBMD (OR 1.39; 95% confidence interval 1.11-1.74) and FRAX score (OR 1.58; 1.27-1.97) in all women combined. Porosity was also associated with fracture independent of FRAX score in subgroups with normal FN aBMD (OR 1.88; 1.21-2.94), osteopenia (OR 1.40; 1.06-1.85), but not significantly in those with osteoporosis (OR 1.48; 0.68-3.23). Of the 211 fracture cases, only 18 women (9%) were identified using FN aBMD T-score < -2.5, 45 women (21%) using FRAX threshold >20%, whereas porosity >80th percentile identified 61 women (29%). Porosity identified 26% additional women with fractures than identified by the osteoporosis threshold and 21% additional women with fractures than by this FRAX threshold. CONCLUSIONS: Cortical porosity is a risk factor for fracture independent of aBMD and FRAX and improves identification of women with fracture.

Does recalled dieting increase the risk of non-vertebral osteoporotic fractures? The Tromsø Study.

UNLABELLED: The risk of non-vertebral osteoporotic fractures increased by increasing recalled amount of weight loss when dieting in women aged ≥ 46 years and in those with BMI < 25 kg/m(2) participating in the Tromsø Study (1994/1995-2009). The increased risk was present both in women with few and several episodes of recalled dieting. INTRODUCTION: The influence of repeated dieting on bone health is uncertain. This study aims to investigate whether recalled dieting is a risk factor for non-vertebral osteoporotic fractures. METHODS: In 1994/1995 weight and height were measured in all participants aged 25-69 years in the population-based Tromsø Study. Information about socioeconomic background, diseases and lifestyle factors was collected by questionnaires-including number of recalled dieting episodes and largest amount of weight loss when dieting. The participating 20,745 women and men were followed for 15 years, fractures were registered from X-ray archives and analysed by Cox's proportional hazards models. RESULTS: Among those who recalled dieting, 975 women and 364 men suffered a non-vertebral osteoporotic fracture during follow-up. Compared to women without recalled weight loss when dieting, women who reported their largest weight loss of 11 kg or more had a hazard ratio (HR) = 1.48 (95% CI 1.13-1.94) for osteoporotic fracture, adjusted for age, marital status, body mass index, height, education, physical activity, smoking, alcohol intake, history of cardiovascular disease and psychological distress. The increased risk was statistically significant only in women aged ≥ 46 years and in those with BMI < 25 kg/m(2). Women who recalled ≥ 11 dieting episodes had HR = 1.73 (CI 1.11-2.68) for osteoporotic fracture compared to those with no recalled episodes. Dieting was not associated with risk of fractures in men, but the number of fractures was low. CONCLUSIONS: The increased risk of non-vertebral osteoporotic fractures by recalled dieting in women indicates that maintenance of a stable weight may have beneficial effects on fracture risk.

Glycated hemoglobin in diagnosis of diabetes mellitus and pre-diabetes; validation by oral glucose tolerance test. The Tromsø OGTT Study.

BACKGROUND: Glycated hemoglobin (HbA(1c)) 6.5% has recently been recommended by the World Health Organization (WHO) and the American Diabetes Association (ADA) as an alternative diagnostic criterion for diabetes mellitus (DM). AIM: To evaluate HbA(1c) as an alternative to oral glucose tolerance test (OGTT) for diagnosis of DM and pre-diabetes and to find the optimal HbA(1c) cut-off points for DM and pre-diabetes in our population. SUBJECTS AND METHODS: The subjects were recruited from the Tromsø Study, performed for the 6th time in 2007-2008 with 12,984 participants. All subjects with HbA(1c) in the range 5.8-6.9% and a random sample of subjects with levels 5.3-5.7% were invited to an OGTT. RESULTS: Among 3476 subjects who completed the OGTT, 199 were diagnosed with DM. The best sensitivity (69.8%) and specificity (81.8%) were found at HbA(1c) 6.2%. For HbA(1c) 6.5% we found a sensitivity of 34.7% and specificity 97.1%. The best cut-off points for impaired fasting glucose (no.=314) and impaired glucose tolerance (no.=404) were found at HbA(1c) 5.9% and 6.0%, respectively. Pre-diabetes detected only by OGTT was associated with worse metabolic characteristics than pre-diabetes detected only by HbA(1c). CONCLUSIONS: The optimum HbA(1c) cutoff point for DM in our population was lower than that proposed by WHO and ADA. To establish more precisely the HbA(1c) levels predictive of micro- and macro-vascular complications, long-term prospective studies are needed. Population- specific optimum cut-off points may be necessary.

BMI change is associated with fracture incidence, but only in non-smokers. The Tromsø Study.

UNLABELLED: Few studies have examined the association between body mass index (BMI) change and fracture in a general population. We observed that BMI loss was associated with increased fracture risk in non-smoking men and women, but not in smokers. BMI gain was associated with decreased fracture risk in women. INTRODUCTION: Weight loss has been associated with increased fracture risk, but few studies have included men. The aim of this study was to examine the association between BMI change and fracture risk in both genders. METHODS: A population-based cohort study in Tromsø, Norway, of adults, aged 20 to 54 years in 1979, who participated in two or three health surveys in 1979-1980, 1986-1987, and 1994-1995. Weight and height were measured at each survey. Information about lifestyle was obtained by questionnaires. Poisson regression was used to estimate incidence rates and Cox proportional hazards regression model to assess the association between fracture risk and BMI change. Fractional polynomials were used to accommodate non-linear associations. RESULTS: A total of 5,549 men and 5,428 women participated. There were 1,135 fractures during 10 years of follow-up. Reduction in BMI was associated with increased non-vertebral fracture risk in non-smokers, but not in smokers. The hazard ratio in male and female non-smokers per 10-year BMI decrease of 2 kg/m(2) versus a BMI increase of 1 kg/m(2) was 1.79 (95% confidence interval (CI), 1.17-2.75) and 1.60 (95% CI, 1.28-1.99), respectively. The association was not significantly modified by initial BMI or age or by exclusion of subjects with cardiovascular diseases, diabetes, or cancer. In female non-smokers, weight gain was inversely associated with fracture risk. CONCLUSIONS: In a general Norwegian population, reduction in BMI was significantly associated with increased fracture risk in male and female non-smokers, but not in smokers. These findings could not be explained by preexisting disease.

Baseline serum 25-hydroxyvitamin D concentrations in the Tromsø Study 1994-95 and risk of developing type 2 diabetes mellitus during 11 years of follow-up.

AIMS: We wanted to test the hypothesis that low serum 25-hydroxyvitamin D (25(OH)D) concentrations are associated with increased risk of developing Type 2 diabetes mellitus (DM) in a population-based cohort during 11 years of follow-up. METHODS: The analyses included 4157 non-smokers and 1962 smokers from the Tromsø Study 1994-95 without diabetes at baseline. Subsequent Type 2 DM was defined using a hospital journal-based end-point registry, completed through the year 2005. Participants were allocated into quartiles of serum 25(OH)D within each month to account for seasonal variation, and serum 25(OH)D values both as a continuous variable and in quartiles were used in Cox regression models. The analyses were stratified by smoking. Adjustments were made for age, sex, body mass index (BMI), physical activity and, in non-smokers, former smoking. RESULTS: Type 2 DM was registered in 183 non-smoking and 64 smoking participants. Using the fourth (highest) quartile of serum 25(OH)D as the reference, non-smoking participants in the third, second and first quartiles had age- and sex-adjusted hazard ratios (95% confidence intervals) of incident Type 2 DM of 1.00 (0.62-1.61), 1.50 (0.97-2.31) and 1.89 (1.25-2.88), respectively, whereas the corresponding values for smokers were 1.79 (0.77-4.19), 2.33 (1.02-5.35) and 2.68 (1.18-6.08). Adjustment for BMI attenuated the hazard ratios, and they were no longer significant. CONCLUSIONS: Baseline serum 25(OH)D was inversely associated with subsequent Type 2 DM in a population-based 11 year follow-up study, but not after adjustment for BMI. Randomized trials are needed to define the possible role of serum 25(OH)D status, and thereby the role of supplementation, in the prevention of Type 2 DM.

Bone loss and the risk of non-vertebral fractures in women and men: the Tromsø study.

SUMMARY: We assessed the association between the rate of forearm bone loss and non-vertebral fracture. Bone loss at the distal forearm predicted fractures, independently of baseline BMD, but not independently of follow-up BMD in women. The BMD level where an individual ends up is the significant predictor of fracture risk. INTRODUCTION: Bone loss may predict fracture risk independently of baseline BMD. The influence of follow-up BMD on this prediction is unknown. The aim of this study was to assess the association between bone loss and fracture risk in both sexes in a prospective population-based study. METHODS: We included 1,208 postmenopausal women (50 to 74 years), and 1,336 men (55 to 74 years) from the Tromsø Study, who had repeated distal and ultra-distal forearm BMD measurements. Non-vertebral fractures were registered from 2001 to 2005. RESULTS: A total of 100 women and 46 men sustained fractures during the follow-up time. Independent of baseline BMD, the RR associated with distal site bone loss of 1 SD %/year was 1.23 (1.01-1.50) for low-trauma fractures (excluding hand, foot, skull & high-trauma) and 1.32 (1.07-1.62) for osteoporotic fractures (hip, wrist and shoulder). However, bone loss did not predict fracture after adjusting for follow-up BMD. The BMD level where an individual ends up became the significant predictor of fracture risk and not the rate of bone loss. Follow-up BMD at ultra-distal site was associated with low-trauma fractures in both sexes. While ultra-distal site BMD changes were not associated with fracture risk in both sexes. CONCLUSION: Bone loss at the distal forearm predicted non-vertebral fractures, independently of baseline BMD, but not independently of follow-up BMD, in women. The BMD level where an individual ends up is the significant predictor of fracture risk and not the rate of bone loss.

Features of the metabolic syndrome and the risk of non-vertebral fractures: the Tromsø study.

INTRODUCTION: We wanted to examine whether the features of the metabolic syndrome carried an increased risk of non-vertebral fracture. METHODS: This is a population-based, 6-year follow-up of 27,159 subjects from the municipality of Tromsø, followed from 1994 until 2001. Age range was 25-98 years. Non-fasting serum levels of high-density lipoprotein (HDL), triglycerides and glucose, blood pressure (BP), weight and height were measured at baseline. All non-vertebral fractures were registered by computerised search in radiographic archives. RESULTS: A total of 1,249 non-vertebral fractures were registered. Increasing number of metabolic syndrome features was associated with significantly reduced fracture risk in both men and women, p= 0.004 and p<0.0001, respectively. High BP was protective against fracture in men [relative risk (RR) 0.89; 95% confidence interval (CI) 0.8-0.99)] while increased body mass index (BMI) was protective in women (RR 0.91; 95% CI 0.84-0.98). Increasing non-fasting serum levels of HDL increased fracture risk in women (RR 1.12; 95% CI 1.05-1.21). BMI modified the effect of HDL in men. Accordingly, high HDL increased fracture risk in men with high BMI (RR 1.51; 95% CI 1.2-1.9). CONCLUSIONS: Increasing burden of metabolic syndrome features protects against non-vertebral fractures. Reduced non-vertebral fracture risk was associated with high BP in men and increased body mass in women. Lower non-fasting serum levels of HDL protect against fractures in women and obese men.

Longitudinal changes in forearm bone mineral density in women and men aged 25-44 years: the Tromsø study: a population-based study.

The aim of this study was to describe and compare bone mineral density (BMD) development in Norwegian women and men aged 25-44 years in a population-based, longitudinal study. BMD was measured twice at distal and ultradistal forearm sites by single x-ray absorptiometry in 258 women and 147 men (mean follow-up time, 6.4 (standard deviation, 0.6) years). At the distal site, a small annual gain of approximately 0.1% became a small loss beginning at age 34 years in men and age 36 years in women. At the ultradistal site, BMD change was predicted by age in women only, and bone loss started at age 38 years. A high degree of tracking of BMD measurements was observed for both sexes and both sites, r > 0.93. Depending on total BMD change, participants were grouped into "losers", "nonlosers", and "gainers", and more than 6% lost more than the smallest detectable amount of BMD: > or =3.46% at the distal site and > or =5.14% at the ultradistal site. In both sexes, bone mineral content (grams) decreased, whereas area (centimeters squared) increased significantly in "losers" compared with "gainers". This finding might represent physiologic compensation preserving bone strength. No cohort effects were observed when 1994 and 2001 measures from similar age groups were compared.

Long-term mental distress, bone mineral density and non-vertebral fractures. The Tromsø Study.

The purpose of this study was to examine, prospectively, the risk of non-vertebral fractures and low bone mineral density in a population-based cohort with respect to indicators of subjective mental distress. In 1979-1980 all males born 1925-1959 and all females born 1930-1959 living in Tromsø were invited (21,441; response rate, 78%). The same individuals were invited to the subsequent studies in 1986-1987 and 1994-1995 (74% attended the first two, and 71% attended all three surveys). Non-vertebral fractures were registered by linkage to the hospital X-ray register for the period 1988-1995, and forearm bone mineral density (BMD) was available in a subsample of 4,690 who had attended three times. Questions about mental distress (depression, insomnia and coping problems) were repeated three times and analyzed as cumulated exposure. Women who reported being depressed at two time points had an adjusted odds ratio (OR) =2.5 (95% confidence interval [CI] 1.3-4.9) for sustaining a non-vertebral fracture and OR=3.1 (95% CI 1.3-7.2) for sustaining an osteoporotic fracture, compared with those without depression on any occasion. The corresponding odds ratios for those with coping problems at two time points were slightly higher, whereas sleeping problems seem only to be weakly associated with non-vertebral fractures. The pattern of associations and the magnitude of OR estimates were mainly the same in women younger than 50 years and those 50 years and older. Women using nerve medicine and reporting depression twice had an odds ratio of 4.4 (95% CI 1.1-17.7) for sustaining a non-vertebral fracture, and those using nerve medicine and reporting coping problems twice had a corresponding OR 4.7 (95% CI 1.2-18.4). Among men no significant associations were found for either fracture type. No association was found between mean BMD and number of times reporting depression, insomnia or coping problems, in women or men. Long-term mental distress is associated with risk of all non-vertebral fractures and osteoporotic fractures in middle-aged women, but not in men. Mental distress itself seems to be more important than the use of nerve medicine.

The Tromsø Study: a population-based study on the variation in bone formation markers with age, gender, anthropometry and season in both men and women.

Background information on how biological factors influence the level of bone turnover markers is crucial in order to make proper use of these measurements. In the present study, which is part of the fourth survey of a general population in Tromsø, Norway, we evaluated the variation in the bone formation markers bone alkaline phosphatase (S-BAP) and osteocalcin (S-OC) in 528 men and 605 women, age 25-74 years. In the Tromsø Study in 1994/5, the whole population above 25 years was initially invited and 7948 individuals attended an extended examination (76.4% of the invited population). The present study population is a random sample of these attendees. The variation with age, gender, height, weight, body mass index and season, and with menopausal status in women, was examined. In men there was a decrease in S-OC up to the age of 56 years with little further change, while S-BAP showed no change with age. Among women, variation in bone markers was mainly observed to change with menopause, with a 41% and 21% increase in the mean level of S-BAP and S-OC, respectively. There was a negative trend in S-OC with body mass index in both men and women. A seasonal change of 20% in the level of both bone markers in men and of S-BAP in postmenopausal women was observed in this region at a far northern latitude. We conclude that, of the factors examined, season and menopausal status must be taken into account when measuring these bone formation markers.

[Vertebral fractures--a big health problem for elderly women?]. / Brudd i ryggen--et stort helseproblem for eldre kvinner?

BACKGROUND: The term osteoporosis often conjures up an image of deformed spines,--small stooping ladies burdened with back pain. Most modern medication against osteoporosis has documented effect first and foremost against vertebral fractures. However, are vertebral fractures a public health issue, and are they frequent and serious enough to warrant aggressive and expensive preventive measures? MATERIAL AND METHODS: Through search in Medline with the terms "osteoporosis", "vertebral fracture*" and "vertebral deformities", we identified and reviewed a total of 222 scientific articles on vertebral fractures. RESULTS: Incident vertebral deformities entail temporary complaints, and the consequences of prevalent deformities are minute unless there are several deformities. Less than 8% of back pain among the elderly can be attributed to vertebral deformities. A large double-blind, randomised clinical trial demonstrates that treatment that halves the risk of new vertebral deformities barely affects the occurrence of back pain or disability. INTERPRETATION: Even if some patients' suffering is attributable to vertebral deformities, we conclude that vertebral deformities represent a minor public health problem. As a consequence, studies exploring predictors of painful vertebral fractures are warranted; furthermore, more documentation on prevention of non-vertebral fractures is needed.

The Tromsø study: registration of fractures, how good are self-reports, a computerized radiographic register and a discharge register?

In order to compare different methods of fracture registration, we sought all nonvertebral fractures suffered during 8 years (1988-95) among 21,441 persons invited to a survey in 1979/80. We registered a total of 54 hip fracture cases through three separate sources (self-report, computer linkage to the local radiographic archives, discharge register), whereas forearm fractures (a total of 291 cases) were registered through two separate sources (self-report, computer linkage to the radiographic archives). The registration of fractures at other sites (a total of 1321 cases) were from one source (computer linkage to the local radiographic archives), and we have compared three ways of obtaining data from this single source (no ascertainment, ascertainment of records coded as fracture, ascertainment of all records). Ninety-three percent of all hip fractures and 97% of all wrist fractures in the entire study population were found by computer linkage to the radiographic archives, whereas the discharge register detected 87% of all the hip fractures. Computer linkage with ascertainment gave no overreporting of fractures. Among the 11,626 persons who answered a follow-up questionnaire in 1994/95, 97% (CI 84-100%) of all hip fractures and 72% (CI 66-78%) of all wrist fractures were self-reported. We conclude that a computerized search of radiographic archives is a viable method of fracture registration.

The Tromsø study: determinants of precision in bone densitometry.

Studies of precision determinants in bone densitometry are scarce. A total of 111 subjects recruited from the population-based multipurpose Tromsø Study (Norway), 27-75 years of age, had repeated forearm bone single X-ray absorptiometry (SXA) measurements. Measurement conditions were systematically varied in series up to eight scans. Median coefficients of variation (CV) for two scans performed 1 week apart, by two different operators were 0.79% and 0.98% at distal and ultradistal sites, respectively. The CV distribution was skewed: 5% of the subjects had individual CVs above 2.2% (distal) and 3.4% (ultradistal). Age (P = 0.0097) and repositioning were important determinants of precision. The SXA bone mineral density (BMD)-measurement method is sufficiently precise to establish BMD level. The minimal individual percentage BMD change that can be detected with 95% certainty was 2% and 3% at distal and ultradistal sites, respectively. Detection of BMD changes less than this should rely on multiple repeat measurements at each point in time.

The Tromsø Study: body height, body mass index and fractures.

Tall persons suffer more hip fractures than shorter persons, and high body mass index is associated with fewer hip and forearm fractures. We have studied the association between body height, body mass index and all non-vertebral fractures in a large, prospective, population-based study. The middle-aged population of Tromsø, Norway, was invited to surveys in 1979/80, 1986/87 and 1994/95 (The Tromsø Study). Of 16,676 invited to the first two surveys, 12,270 attended both times (74%). Height and weight were measured without shoes at the surveys, and all non-vertebral fractures in the period 1988-1995 were registered (922 persons with fractures) and verified by radiography. The risk of a low-energy fracture was found to be positively associated with increasing body height and with decreasing body mass index. Furthermore, men who had gained weight had a lower risk of hip fractures, and women who had gained weight had a lower risk of fractures in the lower extremities. High body height is thus a risk factor for fractures, and 1 in 4 low-energy fractures among women today might be ascribed to the increase in average stature since the turn of the century. Low body mass index is associated with a higher risk of fractures, but the association is probably too weak to have any clinical relevance in this age category.

The Tromsø Study: physical activity and the incidence of fractures in a middle-aged population.

We have studied the relation of occupational and recreational physical activity to fractures at different locations. All men born between 1925 and 1959 and all women born between 1930 and 1959 in the city of Tromsø were invited to participate in surveys in 1979-1980 and 1986-1987 (The Tromsø Study). Of 16,676 invited persons, 12,270 (73.6%) attended both surveys. All nonvertebral fractures (n = 1435) sustained from 1988 to 1995 were registered in the only hospital in the area. Average age in the middle of the follow-up period (December 31, 1991) was 47.3 years among men and 4501 years among women, ranging from 32 to 66 years. Fracture incidence increased with age at all locations among women, but it decreased with or was independent of age among men. Low-energetic fractures constituted 74.4% of all fractures among women and 55.2% among men. When stratifying by fracture location, the most physically active persons among those 45 years or older suffered fewer fractures in the weight-bearing skeleton (relative risk [RR] 0.6, confidence interval [CI] 0.4-0.9, age-adjusted), but not in the non-weight-bearing skeleton (RR 1.0, CI 0.7-1.2, age-adjusted) compared with sedentary persons. The relative-risk of a low-energetic fracture in the weight-bearing skeleton among the most physically active middle-aged was 0.3 (CI 0.1-0.7) among men and 0.9 (CI 0.4-1.8) among women compared with the sedentary when adjusted for age, body mass index, body height, tobacco smoking, and alcohol and milk consumption. It seems that the beneficial effect on the skeleton of weight-bearing activity is reflected also in the incidence of fractures at different sites.

Physical activity and predisposition for hip fractures: a review.

Studies on the association between physical activity and hip fractures are reviewed. All the studies, which comprise four follow-up studies, one nested case-control study and 17 case-control studies, suggest a protective effect of physical activity with regard to hip fractures. The association is strong and consistent with physical activity in leisure, weaker with respect to physical activity at work. The association is present for physical activity from childhood to adult age, and it is consistent in study populations from the USA, Australia, Asia and Northern and Southern Europe, in spite of very different hip fractures incidences in these populations. The magnitude of the association is difficult to assess because of varying criteria for exposure, but to be among the physically active seems to reduce the risk of later hip fracture by up to 50%. It seems that even daily chores, such as climbing stairs and walking, protect against hip fracture.