The Swedish Mammography Cohort And The Cohort Of Swedish Men - Study Design And Characteristics
The Swedish Mammography Cohort and the Cohort of Swedish Men are two ongoing population-based longitudinal cohorts designed to study dietary exposures in relation to chronic disease outcomes.
Author:Suleman ShahReviewer:Han JuAug 21, 20248.1K Shares314K Views
This study discusses two cohorts: the Swedish Mammography Cohort and the Cohort of Swedish Men, established in 1987 and 1997, respectively.
The Swedish Mammography Cohort (SMC) and the Cohort of Swedish Men (COSM) are two large population-based longitudinal cohorts established in Sweden.
The SMC was established in 1987-1990 (together with a mammography screening program) with the aim to explore dietary exposures in relation to breast cancer risk and has since been expanded to assess risk of various healthoutcomes.
The COSM was established 10 years later, in 1997, with the aim to explore diet and lifestyle in relation to chronic diseases.
Since then, additional questionnaire data have been collected and sub-cohorts with biological specimens have been established making these cohorts a valuable resource for the scientific community.
The aim of this study was to discuss the study design and characteristics of these two population-based longitudinal cohorts.
SMC Recruitment
From March 1987 to December 1990, all women living in Uppsala County of central Sweden and who were born in 1914 through 1948 (n = 48,517) and all women living in the adjacent Västmanland County (n = 41,786) who were born in 1917 through 1948 received an invitation by mail to participate in a population-based mammography screening program.
The invitation included a six-page questionnaire that sought information on:
- diet and alcohol intake (a 67-item Food Frequency Questionnaire or FFQ)
- parity
- age at first birth
- family historyof breast cancer
- weight
- height
- education level
- marital status
Women were asked to return the completed questionnaire in-person at their mammogram appointment.
Seventy-four percent of women returned a completed questionnaire.
The final baseline cohort consisted of 61,433 women after excluding the following women from the list:
- those with an incorrect or missing national registration number
- cancer diagnosis (except non-melanoma skin cancer) before baseline
- implausible total energy intake (three standard deviations or SD from the mean value for loge-transformed energy intake)
- those outside the age-range of 38 to 76 years
- those with other missing data
1997 SMC Questionnaire
In the fall of 1997, a second extended questionnaire was sent to all SMC members (n = 56,030) who were still alive and residing in the study area.
The 1997 questionnaire collected information on:
- diet and alcohol intake (a 96-item FFQ)
- dietary supplements
- family history of cancer and myocardial infarction
- age at menarche
- history of oral contraceptive use
- age at menopause
- postmenopausal hormone use
- disease diagnoses
- body weight across the lifecourse (birth weight through weight at age 80 years)
- current waist and hip circumferences
- medication use
The said questionnaire also asked information regarding the person’s lifestyle factors, including:
- history of cigarette smoking
- physical activity (at ages 15, 30, 50, and current)
- sleep habits
The response rate for the 1997 questionnaire was 70%.
After excluding those with an incorrect or missing national registration number, the final 1997 cohort consisted of 38,984 participants.
The SMC population is comparable to the general Swedish population with regards to:
- age distribution
- education level
- body mass index (BMI)
2008 And 2009 SMC Questionnaires
In 2008, a third questionnaire was sent to all cohort members (n = 48,263) that had completed the 1987 FFQ (response rate 63%).
The 2008 questionnaire collected information including:
- general health status
- disease diagnoses
- current body weight
- height
- waist and hip circumferences
- dental health
- medication use
- sleep habits
- urine and bowel habits
- family history of selected diseases
- stress
- social support
In 2009, a fourth questionnaire was sent to women who completed the 2008 questionnaire (84% response rate). The following information were collected:
- diet and alcohol intake (a 132-item FFQ)
- dietary supplements
- smoking
- physical activity
- sun habits
The complete questionnaires can be accessed at: http://ki.se/imm/nutrition-en.
COSM Recruitment
In the fall of 1997, all men born in 1918 through 1952 living in Västmanland and Örebro counties in central Sweden (n = 100,303) received an invitation to participate in the study, along with a self-administered questionnaire.
The questionnaire, the same as used for the SMC in 1997, with the exception of some sex-specific questions, collected information on:
- diet and alcohol intake (a 96-item FFQ)
- dietary supplements
- family history of selected diseases
- disease diagnoses
- body weight across the life course
- current waist and hip circumferences
- medication use
- lower urinary tract symptoms (International Prostate Symptom Score or I-PSS)
The questions regarding lifestyle factors include:
- history of cigarette smoking
- physical activity (at ages 15, 30, 50, and current)
A total of 48,850 (49%) men returned a completed questionnaire via mail.
After excluding some men, the final baseline cohort consisted of 45,906 men.
Those who were excluded were the ones with:
- an incorrect or missing national registration number
- cancer diagnosis (except non-melanoma skin cancer) before baseline
- death before baseline
- other missing data
The COSM population is comparable to the general Swedish population with regards to:
- age distribution
- education level
- BMI (body mass index)
2008 And 2009 COSM Questionnaires
In 2008, a second questionnaire was sent to all COSM members (n = 37,861) who were still alive.
The 2008 questionnaire (78% response rate) collected information, including:
- general health status
- disease diagnoses
- current weight
- height
- waist and hip circumferences
- dental health
- medication use
- sleep habits
- urine (I-PSS)
- bowel habits
- family history of selected diseases
- stress
- social support
In 2009, a third questionnaire was sent to men who completed the 2008 questionnaire (90% response rate). It collected information on:
- diet and alcohol intake (a 132-item FFQ)
- dietary supplements
- smoking
- physical activity
- sun habits
The complete questionnaires can be accessed at: http://ki.se/imm/nutrition-en.
Questionnaire Validation And Reproducibility
Intake of nutrients and total energy were calculated from the food frequency questionnaires using food composition values obtained from the Swedish National Administration Database.
The reproducibility and validity of the FFQs used by the SMC and COSM have been assessed (by comparison with multiple 24-hour recall interviews and/or diet records) for:
- foods
- nutrients
- dietary supplements
- glycemic index
- glycemic load
In addition, FFQ-based estimates of total antioxidant capacity (TAC) have been validated with plasma TAC, and fatty acid dietary intake has been validated with subcutaneous adipose tissue.
Exposure to environmental pollutants via foods has also been validated, including:
- dietary polychlorinated biphenyls (PCB) exposure in relation to PCB concentrations in serum
- dietary cadmium exposure in relation to cadmium urine concentrations
The physical activity questionnaire data have also been validated using 7-day activity records and accelerometers.
Follow-Up Of The Cohorts Through Registry Linkages
Using each participant’s Swedish personal identity number, the SMC and the COSM are linked annually to multiple registries to ensure up to date information on the health status of all participants.
There are two main types of registries in Sweden:
- Health Data Registries
- Quality Registries (national and regional)
Health Data Registries
The Health Data Registries are the responsibility of the Department of Statistics, Monitoring and Evaluation (previously called the Epidemiological Center) at the National Board of Health and Welfare (NBHW) and cover the entire Swedish population.
They include the:
- National Patient Registry, which encompasses the National Inpatient Registry (IPR; also called the Hospital Discharge Registry)
- National Outpatient Registry (OPR)
- Cancer Registry
- Prescribed Drug Registry
The National IPR and OPR contain information about:
- dates of admission and discharge
- hospitals or clinics providing care
- procedures
- main and secondary diagnoses (coded with international classification of disease codes).
National coverage of the IPR has been 100% since 1987, while coverage of the OPR was ~80% in 2007.
As of 2011, 99% of all somatic and psychiatric hospital discharges were registered in the IPR and a primary diagnosis was listed for 99% of all discharges.
A study published in 2011 by the journal BMC Public Health, with Jonas F. Ludvigsson as lead author, made a review of the validity of the IPR.
Ludvigsson et al. found positive predictive values (PPVs) of IPR diagnoses of 85 to 95% for most diagnoses, with PPVs for specific diagnoses of:
- 98 to 100% for myocardial infarction
- 82 to 97% for heart failure
- 99% for stroke/transient ischemic attack
- 87 to 96% for rheumatoid arthritis
- 95 to 98% for hip fractures
- 99% for acute pancreatitis
The Cancer Registry (established in 1958) contains basic information on all individuals diagnosed with cancer in Sweden including:
- site of tumor
- histological type (from 1993)
- stage (from 2004)
The Swedish National Cancer Registry is estimated to be nearly 100% complete.
The Prescribed Drug Registry has been available for linkage since 2005. It contains information about drugs dispensed under prescription at pharmacies, including:
- dispensed amount
- dosage
- substance
- brand name
- formulation
The NBHW is also responsible for the Cause of Death Registry (established in 1961), which includes information about dates and causes of death.
It has been estimated that 93% of all deaths in Sweden are reported to the registry within 10 days and 100% are reported within 30 days.
These Health Data Registries are mandated by law and thus are an excellent source of medical information.
In addition to the Health Data Registries described above, the NBHW also has a Care for the Elderly Registry and Persons with Impairments Registry, both established in 2007.
Besides the registries available through the NBHW, the government agency Statistics Sweden has information available regarding socio-economic status and demographics, including:
- level of education
- income
- employment/unemployment
- early retirement due to disability
- marital status
- regional migration
- immigrations and emigrations
Statistics Sweden is also responsible for the Multi-Generation Registry, through which family linkage (parents, siblings, children, and cousins) and joint linkage with the NBHW may provide opportunities to study family history of diseases.
The Multi-Generation Registry contains information on individuals born from 1932 and onwards.
Quality Registries
The National Quality Registries (approximately n = 73 receiving governmental funding as of June 2013) and regional quality registries contain more detailed clinical information then the Health Data Registries described above.
These registries contain individualized data concerning patient problems, medical interventions and outcomes with the vision of the quality registries to provide data needed for health care quality improvement.
Quality registries that can be linked to the SMC and the COSM include those for:
- Swedeheart
- Heart Failure Registry (RiksSvikt)
- Vascular Registry in Sweden (Swedvasc)
- National Qualify Registry for Stroke (Riks-Stroke)
b. cancer-specific quality registries
- National Prostate Cancer Registry
- National Breast Cancer Registry
- Swedish GynOncology Registry
- Swedish Colon Cancer Registry
Other registries are the:
- National DiabetesRegistry (NDR)
- Swedish National Cataract Registry
- Swedish Renal Registry
- Swedish Rheumatoid Arthritis Registry
Linkage to these quality registries provides detailed clinical data on a variety of conditions.
For example, the NDR (established in 1996) contains a wealth of information on diabetes care, including:
- diabetes type
- diabetes treatment
- body weight
- height
- a hemoglobin A1C (HbA1C) test
- blood pressure
- micro-albuminuria and macro-albuminuria
- blood lipids (from 2002)
- s-creatinine (from 2002)
- abdominal circumference (from 2007)
- physical activity (from 2007)
The National Prostate Cancer Registry (established in 1996) includes information on:
- tumor, node, metastasis (TNM) stage
- Gleason grade
- prostate-specific antigen values and treatment
Additional data have been collected since 2007, including:
- prostate volume
- type of prostatectomy
- type of radiotherapy
The National Breast Cancer Registry (established in 2007) includes information on:
- tumor characteristics (i.e., hormone receptor status)
- TNM stage
- grade
- treatment
- type of surgery
- long-term and short-term complications
- waiting-times for diagnosis and treatment
Prior to 2007, regional breast cancer quality registries allowed for coverage and have provided the SMC with data on tumor and treatment characteristics since 1994 in Uppsala County and since 1997 in Västmanland County.
Through these Health Data Registry and Quality Registry linkages, diagnosis data (with data through 2011) for participants in the SMC and COSM have been obtained, including:
a. cardiovascular disease(n = 31,509)
- 8,004 MI (myocardial infarctions), aka heart attacks
- 9,321 strokes
- 6,719 heart failures
b. type II diabetes(n = 15,200)
c. cancer(n = 20,319)
- 3,608 breast cancers
- 3,969 prostate cancers
d. fractures
- n = 20,027
- 5,917 hip fractures
e. cataract extracts(n = 19,855)
f. deaths(n = 28,726)
- 8,441 cancers
- 12,203 CVDs (cardiovascular diseases)
SMC-Clinical
Recruitment 1
From 2003 through 2009, 8,311 women under age 85 and living in the town of Uppsala received a diet, lifestyle, and physical activity questionnaire, with an invitation to participate in a health examination.
Sixty-five per cent of invited participants completed the questionnaire and 61% participated in the health examination, which included:
- weight, height, waist, hip measurements
- blood pressure
- a dual-energy X-ray absorptiometry scan (n = 5,022)
Also collected at the health exam were:
- blood
- urine
- adipose tissue
Venous blood samples were collected after a 12-hour overnight fast. Samples were immediately centrifuged and separated in a dark room and stored at negative 80 degrees Celsius.
A subset of these women completed an additional FFQ and physical activity questionnaire between 2004 and 2006 (n = 303) and wore a physical activity monitor and completed a 7-day activity record (n = 151).
A second subset of women (n = 116), completed a questionnaire on sun exposure in conjunction with a blood sample collected during the winter months (January-March), and during the summer months (August and September):
- 100 of these women completed the same sun questionnaire
- donated a blood sample
Planned for this clinical sub-cohort in November 2013 were the following:
- a second health examination
- biological sample collection
- diet and lifestyle questionnaire
Recruitment 2
From March 2012 to March 2013, 1,030 women in the SMC who were over age 85 and living in Uppsala County received an invitation to:
- participate in a validated cognitive test phone interview
- complete a FFQ
- receive a home health examination (n = 627, 404 and 309 participants, respectively)
The home health examination included:
- weight, height, waist, hip measurements
- blood pressure
- blood, urine, adipose tissue, and fecal sample collection
- a physical function test
- the Mini Mental State Examination
COSM-Clinical
From May 2010 through June 2013, over 3,000 men in the COSM who were over age 75 and living in Västerås have received an invitation to:
- participate in a validated cognitive phone interview
- complete an FFQ and a one-day food diary
- participate in a health examination
The health examination includes the same data collection as in the SMC-Clinical Recruitment 2 described above.
In addition, the wives of these men who are enrolled in the SMC have also been invited to participate.
Data collection for this clinical sub-cohort is ongoing and, to date, participation in the cognitive phone interview portion is over 83%.
Results
The mean (±SD) age and BMI at cohort enrolment were:
- 52.9 (9.8) years and 24.7 (3.9) kg/m2 for the SMC
- 0.3 (9.7) years and 25.8 (3.4) kg/m2 for the COSM
At baseline, 76% of SMC participants and 82% of COSM participants were married.
In 1997, 13% of SMC participants and 25% of COSM participants were current smokers, and 23 and 15% were regular users of dietary supplements, respectively.
Discussion
Research from the SMC and the COSM has resulted in over 200 scientific peer-reviewed publications.
Important findings in the area of nutrition and cancer include protective associations observed:
- between dietary folate intake and risk of ovarian cancer and pancreatic cancer
- between magnesium intake and colorectal cancer risk
- between vitamin B6 intake and risk of colorectal cancer
- between consumption of fatty fish and kidney cancer risk
The SMC was the first to report a statistically significant interaction between alcohol consumption and hormone replacement therapyfor the risk of estrogen/progesterone-positive breast cancer, indicating that alcohol consumption is more harmful during hormone substitution.
It has also observed an association between long-term dietary cadmium exposure (a proposed endocrine disruptor) and endometrial and breast cancer incidence.
Beyond individual foods and nutrients, we have also reported that metabolic syndrome was associated with an increased risk of age-related cataracts, and that a combination of healthy dietary and lifestyle behaviors could prevent 77% of myocardial infarctions (heart attacks) among women in our study population.
In addition to these etiological studies, our cohorts have been the first to assess the validity of dietary questionnaire for:
- estimates of glycemic load
- total anti-oxidative capacity of consumed foods
- PCB exposure
Moreover, these two were identified as valid biomarkers of long-term dairy fat intake:
- saturated fatty acids pentadecanoic acid (15:0)
- heptadecanoic acid (17:0)
Conclusion
The SMC and the COSM are unique epidemiologic resources with their:
a. population-based design
b. high response rates
c. multiple measures
- 20+ year period (1987 to 1997 to 2008/2009) for the SMC
- 10+ year period for the COSM (1997 to 2008/2009)
This allows for the examination of the associations between long-term diet and lifestyle factors and many different health outcomes.
At present, very few prospective cohorts in Europe or the United States have repeated measurements and very few are representative of the whole population.
In addition, the ability to link these cohorts to the extensive registry data available in Sweden is a strength that allows for near complete assessment of multiple health conditions.
The recent and ongoing data collection in the clinical sub-cohorts will allow for future in-depth analyses that examine health outcomes in an aging population.
Thanks to the Swedish Mammography Cohort and the Cohort Of Swedish Men, there is a bulk of information that can be used in the medical field.
Jump to
SMC Recruitment
1997 SMC Questionnaire
2008 And 2009 SMC Questionnaires
COSM Recruitment
2008 And 2009 COSM Questionnaires
Questionnaire Validation And Reproducibility
Follow-Up Of The Cohorts Through Registry Linkages
Health Data Registries
Quality Registries
SMC-Clinical
COSM-Clinical
Results
Discussion
Conclusion
Suleman Shah
Author
Suleman Shah is a researcher and freelance writer. As a researcher, he has worked with MNS University of Agriculture, Multan (Pakistan) and Texas A & M University (USA). He regularly writes science articles and blogs for science news website immersse.com and open access publishers OA Publishing London and Scientific Times. He loves to keep himself updated on scientific developments and convert these developments into everyday language to update the readers about the developments in the scientific era. His primary research focus is Plant sciences, and he contributed to this field by publishing his research in scientific journals and presenting his work at many Conferences.
Shah graduated from the University of Agriculture Faisalabad (Pakistan) and started his professional carrier with Jaffer Agro Services and later with the Agriculture Department of the Government of Pakistan. His research interest compelled and attracted him to proceed with his carrier in Plant sciences research. So, he started his Ph.D. in Soil Science at MNS University of Agriculture Multan (Pakistan). Later, he started working as a visiting scholar with Texas A&M University (USA).
Shah’s experience with big Open Excess publishers like Springers, Frontiers, MDPI, etc., testified to his belief in Open Access as a barrier-removing mechanism between researchers and the readers of their research. Shah believes that Open Access is revolutionizing the publication process and benefitting research in all fields.
Han Ju
Reviewer
Hello! I'm Han Ju, the heart behind World Wide Journals. My life is a unique tapestry woven from the threads of news, spirituality, and science, enriched by melodies from my guitar. Raised amidst tales of the ancient and the arcane, I developed a keen eye for the stories that truly matter. Through my work, I seek to bridge the seen with the unseen, marrying the rigor of science with the depth of spirituality.
Each article at World Wide Journals is a piece of this ongoing quest, blending analysis with personal reflection. Whether exploring quantum frontiers or strumming chords under the stars, my aim is to inspire and provoke thought, inviting you into a world where every discovery is a note in the grand symphony of existence.
Welcome aboard this journey of insight and exploration, where curiosity leads and music guides.
Latest Articles
Popular Articles