Association between cardiovascular disease- and inflammation-related serum biomarkers and poor lung function in elderly.

BACKGROUND: Cardiovascular disease (CVD) is a common comorbidity in chronic obstructive pulmonary disease (COPD) and reduced lung function is an important risk factor for CVD and CVD-related death. However, the mechanisms behind the increased risk for CVD in COPD patients are not fully understood. METHODS: We examined the association between CVD- and inflammation-related serum biomarkers, and pulmonary function in a geriatric population. 266 biomarkers related to CVD and inflammation were analyzed in blood samples from 611 subjects aged 66-86 years who participated in the Good Aging in Skåne study. Serum levels were assessed by a proximity extension assay. Pulmonary function was measured using the lower limit of normality (LLN) spirometry criteria, i.e., forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) < LLN. Logistic regression models were implemented and multiple comparisons were accounted for. RESULTS: 10.3% of the study participants fulfilled pulmonary function decline criteria according to LLN. Out of the 266 biomarkers, only plasminogen activator, urokinase receptor (PLAUR) was statistically significantly associated with decreased pulmonary function. We could not find a statistically significant association between pulmonary function decline and other biomarkers previously linked to COPD, such as interleukin 6, tumor necrosis factor and surfactant protein D. CONCLUSION: We found that serum levels of PLAUR are associated with pulmonary function decline in older adults. PLAUR is activated following inflammation and promotes matrix metallopeptidase (MMP) activation and extracellular matrix (ECM) degradation. This implies that PLAUR could play a role in the early phase of COPD pathogenesis.

Targeted proteomic analysis of habitual coffee consumption.

BACKGROUND: Coffee drinking has been implicated in mortality and a variety of diseases but potential mechanisms underlying these associations are unclear. Large-scale systems epidemiological approaches may offer novel insights to mechanisms underlying associations of coffee with health. OBJECTIVE: We performed an analysis of known and novel protein markers linked to cardiovascular disease and their association with habitual coffee intake in the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS, n = 816) and followed up top proteins in the Uppsala Longitudinal Study of Adult Men (ULSAM, n = 635) and EpiHealth (n = 2418). METHODS: In PIVUS and ULSAM, coffee intake was measured by 7-day dietary records whilst a computer-based food frequency questionnaire was used in EpiHealth. Levels of up to 80 proteins were assessed in plasma by a proximity extension assay. RESULTS: Four protein-coffee associations adjusted for age, sex, smoking and BMI, met statistical significance in PIVUS (FDR < 5%, P < 2.31 × 10-3 ): leptin (LEP), chitinase-3-like protein 1 (CHI3L), tumour necrosis factor (TNF) receptor 6 and TNF-related apoptosis-inducing ligand. The inverse association between coffee intake and LEP replicated in ULSAM (ß, -0.042 SD per cup of coffee, P = 0.028) and EpiHealth (ß, -0.025 SD per time of coffee, P = 0.004). The negative coffee-CHI3L association replicated in EpiHealth (ß, -0.07, P = 1.15 × 10-7 ), but not in ULSAM (ß, -0.034, P = 0.16). CONCLUSIONS: The current study supports an inverse association between coffee intake and plasma LEP and CHI3L1 levels. The coffee-CHI3L1 association is novel and warrants further investigation given links between CHI3L1 and health conditions that are also potentially influenced by coffee.

Cognitive function in stroke survivors: A 10-year follow-up study.

OBJECTIVES: Post-stroke cognitive impairment (PSCI) has considerable impact on patients and society. However, long-term studies on PSCI are scarce and may be influenced by assessment methods and selection bias. We aimed to (i) assess the prevalence of long-term PSCI; (ii) compare two common cognitive assessment instruments; and (iii) compare cognitive function of long-term stroke survivors with non-stroke persons. METHODS: Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were administered to 10-year survivors from a population-based cohort of first-ever stroke patients included in the Lund Stroke Register, Sweden, in 2001-2002. PSCI was defined as MMSE<27 and/or MoCA<25 and severe cognitive impairment as MMSE<23. Age- and sex-matched non-stroke control subjects who had performed MMSE (but not MoCA) were recruited from the longitudinal population study "Good Ageing in Skåne." The odds of having cognitive impairment for stroke survivors compared to controls were examined with logistic regression analyses adjusting for education. RESULTS: Of 145 stroke survivors after 10 years, 127 participated. MMSE showed PSCI in 46%, whereas MoCA displayed PSCI in 61%. Among the stroke survivors with MoCA<25, 35% had MMSE≥27 (P<.001). The odds of having severe cognitive impairment defined as MMSE<23 were higher among the stroke survivors compared to 354 controls (education-adjusted; OR=2.5; P=.004). CONCLUSIONS: Post-stroke cognitive impairment was prevalent among 10-year stroke survivors, and the odds of having severe cognitive impairment were higher among the stroke survivors compared to non-stroke persons. The burden of long-term PSCI might have been underestimated previously, and MoCA may be more suitable than MMSE to detect long-term PSCI.

No benefit of extended mesenteric resection with central vascular ligation in right-sided colon cancer.

AIM: The optimal extent of mesenteric resection in colon cancer surgery is not known. We have previously shown an increased mortality associated with wider mesenteric resection in right hemicolectomy. This study compares the short- and long-term outcome in three variations of right hemicolectomy based on the position of the vascular ligature in the mesentery. METHOD: In all, 2084 cases of cancer in the caecum or ascending colon were identified in the Swedish Colorectal Cancer Registry and categorized according to the position of the vascular ligature: central ligation of ileocolic vessels (ICVs) ± right colic vessels (n = 390), central ligation of ICVs + right branch of middle colic vessels (MCVs) (n = 1360) and central ligation of ICVs + central ligation of MCVs (n = 334). RESULTS: Neither 3-year overall survival, 3-year disease-free survival nor local recurrence rate differed between the groups (P = 0.604; P = 0.247; P = 0.237). There was still no difference after multivariate analysis adjusted for age, sex, American Society of Anesthesiologists classification, TNM stage and adjuvant therapy. An increased peri-operative mortality, however, was observed in extended mesenteric resections, increasing from 0.8% in non-extended to 3.6% in more extended resection, P = 0.025. CONCLUSION: The study showed no survival benefit by more extended mesenteric resection, indicating that there is no need to extend the mesenteric resection to involve the MCVs in cancer of the caecum or ascending colon. On the contrary, increased peri-operative mortality by more extensive mesenteric resection was noted suggesting that a more conservative approach may be favourable.

Slowing of alternating forearm movements is associated with cognitive impairment in community-dwelling older people.

BACKGROUND/AIMS: Motor impairment is an important aspect of cognitive decline in older adults. It has been suggested that complex motor control is affected earlier than gross motor control. The aims were to investigate if complex hand motor function was more affected than gross motor function in cognitively impaired older subjects, and to present reference values. METHODS: Alternating forearm movements and grip strength were studied in 301 cases, 419 intermediates and 1,207 controls, aged 60-93 years, controlling for demographic, health-related and functional factors and comorbidity. Global cognitive function was assessed by the Mini-Mental State Examination, and episodic memory by 3-word delayed recall. Grip strength was assessed by the Grippit(R). The frequency of alternating movements during 10 s was registered electronically. RESULTS: Alternating movements but not grip strength was associated with cognitive impairment (right: p = 0.006; left: p = 0.022). The mean alternating movements for the 70-year-old male cases compared to the controls were 2.3 versus 2.5 Hz for the right, and 2.2 versus 2.4 Hz for the left arm (p < 0.05), and for the 60-year-old women 2.0 versus 2.3 Hz for the right arm (p < 0.05). CONCLUSION: Complex but not gross hand motor function is associated with early cognitive impairment.

Impact of MDCT with intravenous contrast on the survival in patients with acute superior mesenteric artery occlusion.

Acute thromboembolic occlusion in the superior mesenteric artery (SMA) is a condition with high mortality and morbidity. Multi-detector computerised tomography with intravenous contrast enhancement (MDCTiv) may improve diagnostic accuracy and survival. Patients with acute SMA occlusion were identified between 2004 and 2008 at Malmö University Hospital, Sweden. Medical records were analysed. Each MDCTiv was re-evaluated. A total of 67 patients were identified with SMA occlusion, of which 36 were examined with MDCTiv and ten with plain MDCT without intravenous contrast. In all, 24 (67%) of the 36 patients were correctly diagnosed by MDCTiv at first evaluation. Clinical suspicion of intestinal ischemia followed by a distinct inquiry for intestinal ischemia was associated with trend for a higher rate of correct radiological diagnosis, 18 of 23 (78%), at first evaluation (0.06) but without affecting in-hospital survival (p = 0.27). At re-evaluation, SMA occlusion was found in all cases with MDCTiv, whereas intestinal findings were present in half. In-hospital mortality rate was 42% for patients who underwent MDCTiv, which was significantly lower compared to 90% for the ten patients examined with plain MDCT (p = 0.007) and 71% for patients not examined with MDCTiv or plain MDCT (p = 0.031). Patients that underwent plain MDCT had higher levels of creatinine compared to those examined with MDCTiv (p = 0.005). Patients who underwent intestinal revascularisation, endovascular or open, had higher survival rate (p = 0.001). Examination with MDCTiv in patients with acute SMA occlusion was associated with survival benefit. Hence, MDCTiv seems to be the method of choice in the workup phase. Radiologists should routinely describe the mesenteric vessels in patients with acute abdomen even when the diagnosis is not asked for. Patients with high creatinine levels are at risk to be examined without intravenous contrast, and survival in these patients is poor.

Exposure to cadmium and persistent organochlorine pollutants and its association with bone mineral density and markers of bone metabolism on postmenopausal women.

Environmental contaminants such as cadmium and persistent organochlorine pollutants have been proposed as risk factors of osteoporosis, and women may be at an increased risk. To assess associations between exposure to cadmium and two different POPs (2,2',4,4',5,5'-hexachlorobiphenyl CB-153, 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene p,p'-DDE), on one hand, and bone effects, on the other, in a population-based study among postmenopausal (60-70 years) Swedish women with biobanked blood samples. The study included 908 women and was designed to have a large contrast of bone mineral densities, measured with a single photon absorptiometry technique in the non-dominant forearm. Biochemical markers related to bone metabolism were analyzed in serum. Exposure assessment was based on cadmium concentrations in erythrocytes and serum concentrations of CB-153 and p,p'-DDE. Cadmium was negatively associated with bone mineral density and parathyroid hormone, positively with the marker of bone resorption. However, this association disappeared after adjustment for smoking. The major DDT metabolite (p,p'-DDE) was positively associated with bone mineral density, an association which remained after adjustment for confounders, but the effect was weak. There was no evidence that the estrogenic congener (CB-153) was associated with any of the bone markers. In conclusion, no convincing associations were observed between cadmium and POPs, on one hand, and bone metabolism markers and BMD, on the other.

High Tie or not in Resection for Cancer in the Sigmoid Colon?

BACKGROUND AND AIMS: The optimal extent of mesenteric resection in colon cancer surgery remains elusive. The aim was to assess the impact on perioperative morbidity and oncological outcome depending on the height of central vessel ligation in sigmoid resection for adenocarcinomas. MATERIAL AND METHODS: All cases of stage I-III sigmoid cancers, operated on with locally radical resections (2007-2009), were identified in the Swedish Colorectal Cancer Registry and categorized according to the position of the vascular ligature, that is, ligation of the inferior mesenteric artery, ligation of the superior rectal artery, or ligation of the sigmoid branches. RESULTS: In total, 999 cases were identified and possible to categorize. Although higher ligation level yielded a higher number of lymph nodes, 3- or 5-year overall survival, 5-year disease-free survival, or recurrence rate did not differ between the groups (p = 0.79, p = 0.41, p = 0.67, p = 0.51). No differences in survival were detected after multivariate analysis adjusted for age, sex, T-stage, N-stage, American Society of Anesthesiologists classification, and adjuvant therapy. CONCLUSION: This large population-based study showed increased lymph node yield but no survival benefit or any decreased recurrence rate by high tie in resection of sigmoid cancer.

Cerebral perfusion in the elderly with nocturnal blood pressure fall.

Cerebrovascular disease may be linked with vascular autoregulation in aging. The aim of this study was to examine relation between nocturnal blood pressure (BP) fall and cerebral blood flow (CBF) changes in elderly men. The prospective 'Men born in 1914' cohort study has been in progress since 1968 and included 809 subjects. After 14 years from the last follow up, 97 subjects reached the age of 82 and underwent CBF measurement and 24 h ambulatory blood pressure monitoring. Diastolic BP at night decreased in 84 subjects with median 12.7% and increased in 13 subjects with median 3.7%. Relative diastolic BP fall at night was negatively associated to CBF in temporal and infero-parietal areas. Higher proportion of subjects with increasing systolic BP during the 14-year period was observed in the subgroup with extreme nocturnal diastolic BP dip, irrespectively of BP values or prevalence of hypertension. Extreme nocturnal diastolic BP fall in a cohort of elderly men is correlated with focal changes in CBF. Further studies could explain if increasing BP in the elderly is a cause or result of pathological autoregulation, and if antihypertensive treatment increases nocturnal BP dip.

Formal and Informal Care of Community-Living Older People: A Population-Based Study from the Swedish National Study on Aging and Care.

OBJECTIVES: Study formal and informal care of community-living older people in the Swedish National study of Aging and Care (SNAC). DESIGN: Cross-sectional, population based cohort. SETTING: Three areas in Sweden: Municipality of Nordanstig, Stockholm and Skåne County. PARTICIPANTS: 3,338 persons ≥72 years. MEASUREMENTS: Patterns and amounts of informal and formal care by cognition and area of residence. RESULTS: 73% received no care; 14% formal care; and 17% informal care (7% received both). In the whole study population, including those who used no care, individuals in small municipalities received 9.6 hours of informal care/month; in mid-size municipalities, 6.6; and in urban areas, 5.6. Users of informal care received 33.1 hours of informal care/month in small municipalities, 54.6 in mid-size municipalities and 36.1 in urban areas. Individuals with cognitive impairment received 14.1 hours of informal care/month, 2.7 times more than people with no/slight impairment. In the whole study population, individuals in small municipalities received an average of 3.2 hours of formal care/month; in mid-size municipalities 1.4; and in urban areas, 2.6. Corresponding figures for formal care users were 29.4 hours in small municipalities, 13.6 in mid-size municipalities and 16.7 in urban areas. Formal care users received 7.1 hours, and informal care users, 5.9 hours for each hour/month received by people in the study population as a whole. CONCLUSIONS: More informal than formal care was provided. Informal care is more frequent in small municipalities than urban areas and for those with than without cognitive impairment. The relationship between data on the whole population and the data on users or care indicates that population-based data are needed to avoid overestimates of care.

Associations of central and brachial blood pressure with cognitive function: a population-based study.

Previous observational studies on the association between brachial blood pressure (BP) and cognition have reported conflicting results. Central BP has been hypothesized to be more strongly related to cognition than brachial BP. The aim of this study was to assess the association between brachial as well as central BP and cognitive function, both cross-sectionally and with brachial BP measured 17 years before cognitive testing. The study population comprised 2548 individuals aged 61-85 years at follow-up (61.4% women). The cognitive tests administered were A Quick Test of cognitive speed and the Mini Mental State Examination. In fully adjusted linear regressions, small but significant cross-sectional associations were found between higher BP (systolic, diastolic and pulse pressure) and worse results on both of the cognitive tests (P-values <0.05). No significant prospective associations were found. Central BP did not show a stronger association than brachial BP did. After stratification, significant results were mainly found in the group taking BP-lowering drugs at follow-up. In summary, these findings add to existing evidence on the relationship between BP and cognition, but they do not support a superior role of central compared with brachial BP in the elderly.

Plasma leptin levels correlate to islet function independently of body fat in postmenopausal women.

It has previously been demonstrated that plasma leptin correlates to body fat content. Increased body fat content is accompanied by low insulin sensitivity, which is compensated with increased insulin secretion. We therefore studied whether plasma levels of leptin also correlate to insulin secretion and sensitivity in humans. Therefore, we examined insulin sensitivity by the euglycemic-hyperinsulinemic clamp technique and measured the insulin response to intravenous arginine (5 g) at fasting and 14 mmol/l glucose in postmenopausal women. Percent body fat content was determined with impedance measurements. Log plasma leptin significantly correlated to percent body fat (r = 0.84, P < 0.001). In women with normal glucose tolerance (n = 36), partial correlation studies controlling for body fat content revealed significant correlations between log plasma leptin and fasting insulin levels (r = 0.39, P = 0.029), the insulin response to arginine at both glucose levels (r = 0.38 and r = 0.37, P < 0.036 for both), and the glucose potentiation of arginine-stimulated insulin secretion (r = 0.40, P = 0.025). In contrast, in women with impaired glucose tolerance (n = 17), these correlations were not significant. Plasma leptin did not correlate with insulin sensitivity independently of body fat content. To study whether the correlation between leptin and insulin would be explained by insulin stimulating leptin secretion, we examined plasma leptin during hyperinsulinemic conditions (689 +/- 41 pmol/l), under both euglycemia (5.0 mmol/l, n = 10) and hypoglycemia (2.5 mmol/l, n = 7). However, under both these conditions, plasma leptin was unaltered. In conclusion, plasma leptin 1) reflects body fat content and 2) correlates to insulin secretion independently of percent body fat in postmenopausal women with normal glucose tolerance.

Anthropometric reference data for elderly Swedes and its disease-related pattern.

BACKGROUND/OBJECTIVES: Anthropometric measurement is a noninvasive and cost-efficient method for nutritional assessment. The study aims to present age- and gender-specific anthropometric reference data for Swedish elderly in relation to common medical conditions, and also formulate prediction equations for such anthropometric measurements. SUBJECTS/METHODS: A cross-sectional study among random heterogeneous sample of 3360 subjects, aged 60-99 years, from a population study 'Good Aging in Scania. Means (±s.d.) and percentiles for height, weight, waist-, hip-, arm-, calf circumferences, triceps- (TST) and subscapular skinfold thickness (SST), body mass index (BMI), waist-hip ratio (WHR) and arm muscle circumference (AMC) were presented. The values were estimated based on the prevalence of myocardial infarction (MI), cardiac failure (CHF), stroke, cognitive impairment, dementia and dependence in daily living activities (ADL). Linear regression analysis was used to formulate the prediction equations. RESULTS: Mean BMI was 27.5±5.8 kg/m(2) (men) and 27.2±8.1 kg/m(2) (women). WHR was higher among men (Men: 0.98±0.3, women: 0.87±0.2), except at age 85+ (women: 0.91±0.6). TST was 6.7±0.4 mm higher among women. Men with MI had BMI: 28.6±4.8 kg/m(2) and SST: 21±9.2 mm, whereas subjects with dementia had lower weight (by 9.5±2.9 kg) compared with the non-demented. ADL-dependent women had BMI= 29.0±3.9 kg/m(2), TST=19.2±1.3 mm. CONCLUSION: New normative data on gender- and age-specific anthropometrics on the general elderly population are presented. Cardiovascular diseases are associated with subcutaneous and central adiposity opposed to fat loss with dementia. ADL dependence indicates inadequate physical activity. The prediction models could be used as possible indicators monitoring physical activity and adiposity among the general elderly population hence potential health indicators in health promotion.

High degree of BMI misclassification of malnutrition among Swedish elderly population: Age-adjusted height estimation using knee height and demispan.

BACKGROUND/OBJECTIVES: The degree of misclassification of obesity and undernutrition among elders owing to inaccurate height measurements is investigated using height predicted by knee height (KH) and demispan equations. SUBJECTS/METHODS: Cross-sectional investigation was done among a random heterogeneous sample from five municipalities in Southern Sweden from a general population study 'Good Aging in Skåne' (GÅS). The sample comprised two groups: group 1 (KH) including 2839 GÅS baseline participants aged 60-93 years with a valid KH measurement and group 2 (demispan) including 2871 GÅS follow-up examination participants (1573 baseline; 1298 new), aged 60-99 years, with a valid demispan measurement. Participation rate was 80%. Height, weight, KH and demispan were measured. KH and demispan equations were formulated using linear regression analysis among participants aged 60-64 years as reference. Body mass index (BMI) was calculated in kg/m(2). RESULTS: Undernutrition prevalences in men and women were 3.9 and 8.6% by KH, compared with 2.4 and 5.4% by standard BMI, and more pronounced for all women aged 85+ years (21% vs 11.3%). The corresponding value in women aged 85+ years by demispan was 16.5% vs 10% by standard BMI. Obesity prevalences in men and women were 17.5 and 14.6% by KH, compared with 19.0 and 20.03% by standard BMI. Values among women aged 85+ years were 3.7% vs 10.4% by KH and 6.5% vs 12.7% by demispan compared with the standard. CONCLUSIONS: There is an age-related misclassification of undernutrition and obesity attributed to inaccurate height estimation among the elderly. This could affect the management of patients at true risk. We therefore propose using KH- and demispan-based formulae to address this issue.

Evidence for leptin regulation of food intake in humans.

The adipocyte hormone leptin regulates body weight in mice by decreasing food intake and increasing energy expenditure. Whether leptin is of physiological importance for these processes in humans is, however, not clear. We therefore studied the relation between leptin and habitual food intake in 64 healthy postmenopausal women. Dietary habits were assessed with a modified diet history method. Body fat content was measured using bioelectrical impedance. In the 64 women, aged 58.6+/-0.4 yr (mean+/-SD), serum leptin was 19.3+/-12.7 ng/mL, body mass index was 25.0+/-3.5 kg/m2, body fat content was 31.6+/-4.3%, fasting glucose was 4.6+/-0.5 mmol/L, and fasting insulin was 56+/-21 pmol/L. Leptin levels were negatively correlated to total energy intake (r=-0.34; P=0.006), carbohydrate intake (r=-0.36; P=0.004), and total (r=-0.27; P=0.034) as well as saturated fat intake (r=-0.31; P=0.014). Leptin was correlated to the absolute, but not to the percent, intake of these nutrients. When normalized for body fat content, the correlations remained significant. Our results suggest that plasma leptin is involved in the physiological regulation of food intake in humans, and that leptin is related to the quantity rather than the quality of habitual food intake.

Quality control program for storage of biologically banked blood specimens in the Malmö Diet and Cancer Study.

A biological bank has been developed to extend the biochemical and molecular research base for a prospective study on diet and cancer in the city of Malmo, Sweden. The study entered individuals 45-69 years of age, of which 30,382 individuals (45%) participated. Each individual entering the bank has stored samples of viable mononuclear leukocytes (MNLs; -140 degrees C) and granulocytes (GRANs; -80 degrees C) or buffy coats (-140 degrees C), erythrocytes (-80 degrees C), and plasma/serum (-80 degrees C). The bioassays developed to monitor the quality of storage conditions were: (a) viability and growth response to phytohemagglutinin for MNLs; (b) DNA strand breakage for GRANs; (c) NAD content for erythrocytes; and (d) thiol status for plasma/serum. The yield, purity, and storage conditions were all quality controlled, and the samples were determined to be of high standard after 137-190 weeks of storage. No differences in yield and purity were found in samples banked by different laboratory technicians. Growth responses of MNLs were severely reduced (90%) after 40 weeks of storage, which justified switching from the storage of purified MNLs and GRANs to the more cost-effective banking of buffy coats. We conclude that the quality of the banked material, based on the biochemical analysis done, indicate that the storage conditions are optimal at least up to 3.5 years, except for the growth response of MNLs.

Feasibility and quality of biological banking of human normal and tumor tissue specimens as sources of DNA for the Malmö Diet and Cancer Study.

Human tumor and normal tissue specimens, which were collected from autopsy material 1-6 days postmortem, were compared with similar tissue specimens collected within 2 h after surgical resection and transport to the pathology department. The end point criteria used to evaluate the quality of the specimens for biological banking purposes were the extractability and yield of high molecular weight DNA and UV absorption ratios at 260:280 after collection and immediate storage of the specimens at -80 degrees C. The data demonstrated that autopsy material was a quality source of DNA, although of not such high quality as surgical biopsy specimens <2 h after resection. The advantages of using autopsy material to supplement surgical specimen collection sent to pathology, as opposed to using specimen collection at surgery wards or formalin-fixed material, as sources of DNA are: (a) large amounts of tumor and normal tissues from a variety of organ sites can be obtained without regard to the patient's health status; (b) a higher percentage of retrieval of incident cases of cancer in prospective designed trials is more likely to be achieved; and (c) the extractable DNA is of sufficiently high enough quality to permit direct analyses by molecular hybridization and sequence methodologies.

Bias in diet assessment methods--consequences of collinearity and measurement errors on power and observed relative risks.

BACKGROUND: If several risk factors for disease are considered in a regression model and these factors are affected by measurement errors, the observed relative risk will be attenuated. In nutritional epidemiology, several nutrient variables show strong correlation, described as collinearity. The observed relative risk will then depend not only on the validity of the chosen diet assessment method but also on collinearity between variables in the model. METHODS: The validity of different diet assessment methods are compared. The correlation coefficients between common nutrients and foods are given using data from the Malmö Food Study. Intake of nutrients and foods were assessed with a modified diet history method, combining a 2-week food record for beverages and lunch/dinner meals and a food frequency questionnaire for other foods. The study population comprised 165 men and women aged 50-65 years. A multivariate logistic regression model is used to illustrate the effect of collinearity on observed relative risk (RRo). RESULTS: A moderate to high correlation between risk factors will substantially influence RRo even when using diet assessment methods with high validity. Methods with low validity might even give inverse RRo. CONCLUSION: It is stressed that caution must be exercised and only a selected number of variables should be included in the model, especially when they are highly intercorrelated, since RRo might be severely biased.

The Malmö Food Study: validity of two dietary assessment methods for measuring nutrient intake.

BACKGROUND: Nutritional epidemiology relies largely on dietary assessment methods for the estimation of the "exposure' variables which may be related to disease risk. METHODS: This paper describes a methodological study conducted in Malmö, Sweden, to compare nutrient intake--estimated by two alternative dietary assessment methods--with a reference method consisting of 18 days of weighed food records. The two candidate methods were an extensive food frequency questionnaire with portion size to be estimated from a booklet of 120 sets of photos (method A) and a method involving the combination of a shorter questionnaire and a two-week food record (method B). RESULTS: In absolute values, both methods overestimated nutrient intake by 20-40%, with method B closer to the reference for most nutrients. Both crude and energy-adjusted correlations between A-reference and B-reference were of the order of 0.50-0.60 for energy, energy-providing nutrients and most vitamins and minerals. Correlations were in the same range for most of the 14 fatty acids considered in the analyses. Protein intake, estimated from the analyses of urinary nitrogen on 6-8 repeated 24-hour urine collections per subject, was almost identical to the reference method values. Correlation between nitrogen-derived values and dietary measurement was 0.75. CONCLUSIONS: Overall, the study indicated that both methods A and B had good ranking validity compared to the reference and that in most cases the combined method (B) performed slightly better than the extensive food frequency method (A).