J7ournal of Epidemiology and Community Health 1993; 47: 103-108

Trends in body mass index and prevalence ofobesity in Swedish men 1980-89

Alicja Kuskowska-Wolk, Reinhold Bergstrom

AbstractStudy objective-To assess changes in thebody mass index (BMI, weight (kg)/height2(m2) and in the prevalence of obesity inSwedish men during the 1980s.Design-Data from two successive cross sec-tional surveys were used.Setting-The whole of Sweden.Participants-Subjects included in theanalyses were 7055 men from a 1980-81 sur-vey (response rate 83-4%) and 6081 men froma 1988-89 survey (response rate 79%). Menwere aged 16-84 years and were arepresentative sample of Swedish males.Measurements and main results-The resultswere based on self reported weight and heightobtained during interview. After adjustmentfor sociodemographic variables, a significantincrease in the mean BMI ofthe entire popula-tion of men was found between 1980-81 and1988-89 (0-23 kg/m2; p<0.001), with a particu-larly large increase in the 25-34 year age group(0-45 kg/m2; p<0-0001) which corresponds to 14kg for a man 180 cm tall). In manual workersthis value was 0-25 kg/m2 (p<0.0005). Thisincrease was also reflected by a significantrelative increase in the prevalence ofthe com-bination of overweight and obesity (BMI >25kg/m2) of about 190/o (odds ratio=119, 95%confidence intervals: 109, 1-29).Conclusions-During the 1980s the meanBMI and the prevalence of overweight andobesity among adult Swedish men increased.

J Epidemiol Commiiunity Health 1993; 47: 103-108

Cancer EpidemiologyUnit, UniversityHospital, S751 85Uppsala, SwedenA Kuskowska-WolkR BergstromHealth BehaviourResearch, KarolinskaInstitute, Stockholm,SwedenA Kuskowska-WolkDepartment ofStatistics, UppsalaUniversity, Uppsala,SwedenR Bergstrom

Correspondence to:Dr A Wolk

Accepted for publicationSeptember 1992

Information programmes and treatment of obesityare common in many countries. The effectivenessof these preventive methods in an entirepopulation-that is, in different sociodemo-graphic groups-is ofgreat interest since obesity isassociated with a number of medical and psycho-social complications.' 2 Higher rates of mortalityamong obese subjects have also been reported.3-It is therefore important to investigate trends overtime in the body mass index (BMI) and in theprevalence of obesity in different countries.Changes in the BMI and the prevalence of obesityover time in men have recently been investigatedin the USA,6-'0 Italy," Finland,'2 Denmark,'3 '4The Netherlands, 15 and Czechoslovakia.'6 InSweden, there is no information on these trends.Earlier studies have reported an inverse relationbetween sociodemographic status and obesity inwomen. 17-30 The associations found betweensociodemographic factors and obesity in men,

however, have been weaker, more variable, and6 18-22 24-29 31-35less consistent.

Data from twvo successive cross sectional sur-veys were used to study changes in the BMI andprevalence of obesity in Swedish men between1980-81 and 1988-89. Adjustments were madefor possible differences in age, education, socio-economic class, geographical region, and nation-ality, between these two study periods. Therelations between sociodemographic variables andBMI and the prevalence of obesity are also pre-sented.

MethodsData from two national surveys on livingconditions-Undersokning av Levnadsforhal-lande (ULF) 1980-81 and ULF 1988-89- wereused for the analyses. These surveys were designedand conducted by Statistics Sweden (the officialstatistical organisation). Questions about weightand height were included among about 200 otherquestions covering many aspects of living condi-tions. Nationally representative samples ofSwedishmen aged 16-84 years who resided permanently inSweden were chosen for each survey.The procedure for data collection was the same

in 1980-81 and 1988-89, and most of the datawere collected during a personal visit by aninverviewer. Some interviews were performed bytelephone when there was no reply or when theinterviewee requested it.Weight and height were self reported by sub-

jects, without an objective check by the inter-viewer, although the latter would have reacted inthe event of an obvious discrepancy between theobserved stature and the reported values.The validity and reproducibility of these self

reports on weight and height have been studiedand previously reported.36-37 The response rate in1980-81 was 83-4% and in 1988-89 it was 79%.The number of study subjects, broken down bysociodemographic group and year of the survey, ispresented in table I. Details of the surveys aregiven elsewhere.37We computed the body mass index (BMI) using

the widely accepted method ofweight (kg) dividedby the square of height (m2) .38 The criteriarecommended by the FAO/WHO/UNU expertconsultation in 1985 were used to assess theprevalence of obesity in Swedish men.39 The cutoff points for BMI were as follows:

BMI=25-30 kg/m2-overweight (obesity gradeI40);

BMI >30 kg/m2-obesity (obesity grade II andupwards40).

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STATISTICA

In the analy:standard reimade it pow

Table I Body nmass index in nationally repr4group, education, socioeconomic group, regioon1980-81 and 1988-89 (mean (SD)).

Characteristics

Age group (y):16-2425-3435-4445-5455-6465-7475-84

Total 16-84

Education:Elementary school,<9v

High school, 10-11 y

After high school 12-14 y

University, >14 y

Unspecified*

Socioeconomic group:

Manual workersJunior salaried employeesIntcrmediate salaried employcesSenior salariedemployees and

self employed professionalsFarmersEntrepreneursStudents

Region:HI StockholmH2 Gothenburg and MalmoH3 Large municipalitiesH4Southern/central Sweden, excluding 1-3H5 Northern densely populated area

H5 Northern sparsely populated area

Nationality:Nativeborn SwedishSecond generation immigrantsNaturalized immigrantsForeign nationals

*In the 1980-81 study, men older than 74 years

Table II Influence ofdifferent variables on t(regression parameter esti.mates with standard

L METHODS explanatory variable-study period, age,

ses with BMI in a continuous form, the education, socioeconomic group, region, and eth-gression model was used. This model nic origins after adjustment for the effects of thessible to estimate the effects of each other variables. The explanatory variables were

used in categorical or categorised form. In theesentative samples of Swedish men by age regression models, each variable was representedand nationality for two study periods, by suitably chosen dummy variables in such a way

that one of the categories of each variable served asBody nmass index (kglni2) the reference category (period 1980-81, age group1980-81 1988-89 16-24 years, etc as shown in table II). TheNo( Mea (S) N Men (D) estimated parameters show the differences with

regard to this reference group. Thus, the para-1117 22 20 (2 54) 998 22 27 (2 76) meter 023 in table II suggests that after1291 23 48 (2978) 1032 23-89 (285) adjustment for the effects of other variables the1195 24-45 (2-92) 1122 24-59 (3-02)847 25 12 (3 04) 976 25-23 (319) BMI was 0-23 units higher in the time period936 25239 (318) 683 25-69 (333) 1988-89 than in 1980-81.785 25-20 (3-19) 782 25-30 (3-20)884 24 70 (3 18) 488 24-64 (328) In the analyses of the proportion of overweight

7055 24 24 (3.15) 6081 2441 (325) and obesity, the logistic regression model, esti-

2719 24.49 (341) 2254 24.62 (3.50) mated by the maximum likelihood method, was

1580 24 09 (3 00) 1754 24 48 (328) used. If the proportion of overweight and obesity1417 2348 (2 73) 15506 23474 (2973) (or obesity only) is represented by P, this model884 24 70 (3-18) -- - assumes that the logarithm of the odds (P/(1-P))

of being, for example, obese is a linear function of3306 2451 (318) 2698 24 72 (338) explanatory variables. From the estimated541 24-31 (3-13) 573 24-45 (2-94)904 24 11 (278) 874 24-22 (2-98) parameters of this model, odds ratios (ORs) were

699 2401 (2 79) 730 24 30 (2-91) computed.593 24-87 (323) 505 25 16 (318) The OR of, for example, obesity in 1988-89427 25500 (312) 213 25 21 (315) compared with 1980-81 is defined as (PI/(1-PI))/

(PO/(1-Po)) where P0 and P1 represent the risks of1192 23-75 (310) 986 24 00 (3 34) being obese in 1980--81 and 1988-89,22013 24 30 (3-128)2012 24-342 (306) respectively.The OR is a measure of the relative1676 2441 (3-14) 1374 24-68 (328) risk (RR) of being obese and is close to the RR547 24318 (2-98) 44324543 (3.26) when the absolute risks are reasonably small.

When the RR is larger than 1, the OR is always6288 24-25 (3-12) 5345 24-40 (3-22) larger than the RR, and for large absolute risks the242 23-32 (3-25) 276 23-86 (3-35) . ' .c226 24-67 (3-23) 244 25-02 (3-32) difference can considerable (with P1=05 and

295 24-27 (3-46) 206 24-63 (363) P0=0-4 the RR=1*25 and the OR=1*50) Thiswcre not askcd about their education should be kept in mind when the OR values are

interpreted. In very general terms the OR of1 15the bodynmass index of Swedish men

errors)

VariablesInterceptStudy 1980-91 (ref)Study 1988-89Age group (y):

16-24 (ref)25-3435--4445-5455-6465-7475-84

Education:Elementary school, .9 y (ret)High school,0 0-1 yAfter high school, 12-14 y

University, > 14 y

Socioeconomic group:

Manual workers (ret)junior salaried employeesIntermediate salaried employeesSenior salaried employees and self employed

professionalsFarmersEntrepreneursStudents

Regions:HI Stockholm (ret)H, Gothenburg and Malm6Hi Large municipalitiesH4 Southern/central Sweden, excluding 1 -3H5 Northern densely populated areas

H,H Northern sparsely populated areas

Nationality:Native born Swedish (ret)Second generation immigrants

Naturalised immigrantsForeign nationals

(ref)=reference group

Stanidard - TbeIIEfect of the time period on the body massEstimate error p value index (BMI) of Swedish menin different age groups afterl

____stssae rrr p alcadjustnment for the effect of education level, soci oeconomi c

22 36 0 11 group, region, and nationality. Theintercept shows themean BMI (kglm2) for an individualin the reference

0-23 0-06 0-001 group in 1980-81. The slope param eter shows the

difference in BMI between 1980-81 and 1988-89.1221 0-10 0-0001 Age group (y) Initercept (SE) Slope (SE)

2-07 0-10 0.0001

2-65 0-11 0-0001 16-24 22-27 (0-20) -0-03 (0-12)2-97 0111 0-0001 25-34 23-62 (0-21) 0-45 (0)12)*2-59 0-11 0-0001 35-44 25-02 (0-20) 0-23 (0-12)1-88 0 16 0-0001 45-54 25-00 (0-24) 0-21 (0-15)

55-64 2487 (0-24)0227 (0-16)65-74 24-89 (026) 0-14 (0-16)

-0-10 0-07 001767 75-84 2434(0327) 0-16(0121)-0-27 0-08 0-0007 Total 16-84 24-37 (0-09) 0.26 (0-06)*-0-96 0-13 000001 * p < 0 - 01

-0-31

-0-43

-0-29

0-09

-0-06

-1-37

0 0100-09

0-11

0-10

0-13

0-13

0-0017

00000 1

0-01030-3859

0-6101

0-0001

0-43 01 10 01 0001

0-35 0-08 0-0001

0-43 0-09 0000010-38 0-12 0-0011

0-62 0-12 0-0001

0-27 0-14 0-0481

0-30 0-14 0-0355

0-51 0-14 0-0002

Table IV Effect of the time period on the body massindex (BMI) of Swedish men in different socioeconomicgroups after adjustment for the effect of age, education,region, and nationality. The intercept shows the meanBMI for an individual in the reference group in 1980-81.The slope parameter shows the difference in BMI between1980-81 ard 1988--89.

Socioeconomic groups Intercept (SE) Slope (SE)Manual workers 22-42 (0-17) 0-25(0-09)*junior salaried employees 22-46 (0.38) 0-08 (0-18)Intermediate salaried

employees 21-75 (0-35)0-21(0-14)Senior salaried employeesand self employedprofessionals 2372 (0-67) 0-29 (0-15)

Farmers 22-60 (0-61)0-28 (0-21)Entrepreneurs 2431(1-45) 0-20 (0-33)All socioeconomic groups 21-76 (0-10) 022 (0-06)t*p<05005< tp<0-0001

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for the period 1988-89 (table VI) means that theRR ofbecoming obese was 15% higher in 1988-89than in 1980-81.When comparing 1980-81 with1988-89 we shall sometimes use the expression'trend' in BMI. It should be kept in mind,however, that only two observation points areavailable and we cannot say whether this is a trendin the true sense of the word.

In all of the regression analyses, the actualsample values were used without any weighting ofthe observations.

ResultsEIGHT YEAR TRENDS IN MEAN BMIThe crude mean BMI increased by 0 17 kg/M2between 1980-81 and 1988-89 (table I). Afteradjustment for such sociodemographic variablesas age, education, socioeconomic group, region,and ethnic origin, the difference increased to 0-23kg/M2 (p<0.001) (table II). This is a 1% increaseover the eight year period. For a man with anaverage height of 180 cm, the increase cor-resnonds to over 0.7 k. Table III shows the eiahtyear trendseparately.25-34 ye(P<0 OO 1man of avemic groucantly higi(0-25 kg/rithe increasemployeesdid not realsmaller nu:

Table V Prevalence of individuals with boBMI >30 kg/m2 in nationally representativeeducation, socioeconomic group, region, andand 1988-89.

CharacternsticsAge group (y):

16-24

25-34

35-44

45-54

55-64

65-74

75-84

Total 16-84

Education:

Elementary school, <9 yHigh school, 10-1 yAfter high school 12-14 yUniversity, >14 yUnspecified

Socioeconomic group:Manual workers

Junior salaried employeesIntermediate salaried employeesSenior salaried employees and

self employed professionalsFarmers

EntrepreneursStudents

Region:H, Stockholm

H2 GothenburgH3Large municipalitiesH4 Southern/central Sweden, excluding 1-3

H,5Northern densely populated areaH6 Northern sparsely populated area

Nationality:Native born Swedish

Second generation immigrantsNaturalised immigrantsForeign nationals

EIGHT YEAR TRENDS IN THE PREVALENCE OFOVERWEIGHT AND OBESITYTable V presents the crude percentages of menwith BMI >25 kg/m2 (overweight and obese) andwith BMI >30 kg/M2 (obese) in different socio-demographic groups according to the year of thesurvey. The above mentioned increase in the meanBMI was also observed in the analyses with BMI incategorised form. Table VI shows a 19% relativeincrease in the prevalence of men with BMI >25kg/M2 in adult Swedish men over the eight yearperiod. In absolute values, the prevalence ofoverweight and obesity increased by about0*13%/year. The greatest relative increase in theprevalence of BMI >25 kg/M2 took place in the25-34 year age group (OR= 1 -36, 95% confidenceinterval (CI): 1-12, 1 65) and among senior sal-aried employees and self employed professionals1-41; 1 10, 1*80) (tables VII and VIII). Theprevalence of obesity (BMI >30 kg/M2) was notsignificantly different in 1988-89 and 1980-81 forany specific age or socioeconomic group.

- -DB VSOCIODEMOGRAPHIC TRENDS IN BMI AND THE

Is in mean BMI for each age group PREVALENCE OF OBESITYThe greatest increase, seen in the

age group,stwncrease, seen kin 2 Tables II and VI show quantitative estimates ofthese relations. The BMI in men is largely),which corresponds to 1-4 kg for a determined by age, the highest mean values occur-

-rage height. In the various socioecono-nng in the 55-64 year age group. In this group the

ier BMI in 1988-89 than in 1980-81 prevalence of BMI >25 kg/M2 is up to sevenfoldi2; p<0005). The point estimates for higher and the prevalence of obesity up to sixfoldse in mean BMI among senior salaried higher than in young men 16-24 years of age.and farmers were even higher, but they A clear trend is present-- that is, Swedish men

statistical significance because of the with a higher education tend to have a significantlymber of observations (table IV). lower BMI. The difference between men with a

university degree and those with only an

elementary school education amounts to about 1

dy mass index (BMI) >25 kg/M2 and with kg/M2, which corresponds to 3-2 kg for a man 180e samples of Swedish men by age group, cm tall. In the highest education group, thenationality for two study periods 1980-81 prevalence of BMI >25 kg/M2 is about 50% lower

and the prevalence of obesity about 60% lowerBMI>25kgnBMI >30 kg/n2 than in the elementary education group.

1980-81 1988-89 1980-81 1988-89 Junior, intermediate, and senior salaried(%/6) (%6) (%) (%) employees and self employed professional men all11-4 13.1 1-5 11 have a significantly lower BMI than manual work-2359 2887 249 2 8 ers. The mean BMIs offarmers and entrepreneurs35-7 38-5 4-5 6-145-6 47-7 6 1 7-2 do not differ from those of workers. The preva-5042 540737 888 lence ofBMI >25 kg/M2 is also significantly lower49-3 50-3 7-8 7-241 5 41-0 5-6 6-5 among junior, intermediate, and senior salaried35-0 37-4 4 9 5-3 employees than among manual workers. Obesity40-9 41 8 63 6-9 occurs significantly less often in intermediate31i8 38 9 4-2 5-0 salaried employees. Changes in the BMI with29-3 32-9 3-3 48229 290 28 18 increasing age vary substantially between socio-41 5 - 5 6 - economic groups. The mean BMI of senior sal-

38-9 41 1 5-4 6.4 aried employees and self employed professional34 4 37-1 4-9 5-0 men remains relatively stable throughout life, with31 0 33.3 3.7 3-8 the greatest difference, 1-2 kg/M2 (p=0 05), in the

28.6 35-3 3 3 4 0 55-64 year age group compared with the men4486 47 4 7-9 861 aged 16-24 years. In contrast, farmers in the same48-7 52-1 5.9 6-310-6 13-0 2-0 1-4 age group increased their mean BMI by 3-3 kg/mi

(data not shown in tables).2796 31441 0 552 Compared with men from Stockholm, all other35.9 36-1 5.7 5.536-3 38-1 5-5 4-2 geographical regions in Sweden have significantly36 1 36°3 3467 56 higher BMIs. The most striking difference, seen in37-4 46-5 4-6 8-2 the northern sparsely populated areas (0-62

35 1 37 1 4.7 5 4 kg/m2), corresponds to 2 kg for a man 180cm tall.25-2 34-4 4-6 3-1 The prevalence of BMI >25 kg/m2 is about42-0 43.7 7-7 6-6 30-40% higher in all regions other than34-6 40-5 6-8 42 Stockholm.

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Table VI Prevalence of overveight and obesity (body niass inldex (BMI) >25 kg/1n2)anld obesity (BMI >30 kg/ni2) in niationially representative samilples of Swedish nien byyear of study, age, education, socioecononiic group, regioni, and nationality afteradjustnient for the effects of the other variables (odds ratios (OR) with 95 % confidenceintervals (CI)).

I 'ariablesStudy 1980-81 (ref)Study 1988-89Age group (y):

16-24 (ref)25-3435-4445-5455-6465-7475-84

Education:Elementary school, <9 y (ref)High school, 10-11 yAfter high school, 12-14 yUniversity, > 14 v

Socioeconomic group:Manual workers (ref)Junior salaried employeesIntermediate salaried employeesSenior salaried employees and

self employed professionalsFarmersEntrepreneursStudents

BMI >25 kg/rn2 BMI >30 kgl/ni2OR 95%'. CI OR 95% CI

1-19 1-09, 1-29 1 15 0(97, 1-37

2-303 885 526 625 603.57

192, 2 743 24, 4 634 59, 65645.49, 7-994-64, 6 772 77, 4 59

2-28 1-37, 3.794 11 251, 6724.99 304, 8 186-28 3-84, 10 3519 315, 8544 03 2 20, 7-37

0 90 0 81, 0 99 0 78 0-63, 0 970 76 0-67, 0 85 0 71 0 55, 0 910 53 0 44, 0 65 0 36 0 21, 0(60

0 810 75

0 801 071 050 38

0 70, 0 940 66, 0-85

0 68, 0-950-93, 1-230-89, 1-260-29, 0 50

Region:HI Stockholm (ref)H2 Gothenburg 1 30 1 13, 1 50H3 Large municipalities 1 29 1 14, 1 45H4 Southern/central Sweden, excluding 1 3 1 30 1 14, 1 48H5 Northern densely populated areas 1 29 1 08, 1-54H, Northern sparsely populated areas 1 46 1 23, 1 75

Nationality:Native born Swedish (ref)Second generation immigrants 1-39 1-12, 1-73Naturalised immigrants 1-17 0 95, 1-43Foreign nationals 1-33 1-08, 1 64

0 860-67

0-811 220-790 48

1 260.991 050 981-15

0-64, 1-160*50, 090

056, 1 170 94, 1 570.55, 1-150 23, 1-01

0 94, 1 700-76, 1 290 80, 1 380 67, 1 440 80, 1-66

1 22 0-74, 2 011 34 0-92, 1 961 48 099, 221

Native born Swedish men have a significantlylower mean BMI (after adjustment for age,education, socioeconomic group, and region)than those of all other ethnic groups living inSweden. The prevalence of BMI >25 kg/M2among native Swedes is significantly lower thanthat among second generation immigrants andother ethnic groups.

Finally, it should be pointed out that althoughwe have noted very significant effects in manycases, the regression model presented in table II(including variables such as the study period, age,education, socioeconomic group, region and eth-nic origin) explains only 14% of the variance inBMI among Swedish men (R2=0- 14).

DiscussionOur study has two important features: firstly, a

large number of representative subjects, and sec-

ondly, available data on many sociodemographicvariables that make it possible to adjust for them inthe analyses.

TIME TRENDS IN BMI DEVELOPMENTAccording to the data from the two ULF cross

sectional surveys, there is a statistically significantincrease in the mean BMI among Swedish adultmen during the 1980s when adjusted for age,education, socioeconomic group, region, and eth-nic origin. In every age group from 25 years up to

84 years, and among most socioeconomic groups,the mean BMI has increased. Our findings, ingeneral, confirm and extend similar observationsmade in surveys carried out in the USA andEurope.6 15

A report using American data on men aged35-74 years who participated in four nationwidesurveys in 1960-80 (NHES I and III; NHANES Iand II) indicated an increase in the mean BMI forall age groups.6 No consistent trend was found inmen aged 18-34 years from the same surveys.78In the Minnesota Heart Survey the age adjustedmean BMI of men aged 25-59 years increasedsignificantly by 1 kg/M2 from 1973 to 1987.9 Asignificant increase in BMI, adjusted for age andeducation, was found between 1980 and 1987 in asample of men aged 25-74 years (0-8 kg/m2/yearover seven years) from the Minnesota HeartHealth Programme. A furthet analysis of these dataindicated that the weight increase was noticeableonly in the 30-39 and 50-59 year age groups."'The results from European countries are more

heterogeneous. In Italy, the mean BMI of menaged 20-59 years in 1983-84 did not change inrelation to the mean BMI of people examined in1978-79 in the nine communities study." Threepopulation surveys in eastern Finland, carried outin 1972, 1977, and 1982, each included about1600 men aged 30-59 years. In men aged 30-39years, the mean BMI remained stable between1972 and 1982; in those aged 40-49 years themean BMI increased by 1 1 kg/M2; and in those50-59 years of age it increased less noticeably. '2 Itshould be noted that the mean BMIs of Italian andFinnish men were not adjusted for age or othersociodemographic characteristics of the subjects.The 25th, 50th, and 75th centiles for BMI of18 year old Danish men remained essentiallyunchanged over 20 years between 1957 and1976.13 Data from two screening projects con-cerning cardiovascular risk factors were used toinvestigate trends in BMI in The Netherlands in1974 and 1986. The mean BMI of 14 000 menaged 37-43 years examined in the period 1974-80, showed an increase of 0 5 kg/m2 (adjusted forage and town). In the period 1981-86 there was nochange in the mean BMI of 80 000 men aged33-37 years in The Netherlands; however, someregional differences were noted.'5

TIME TRENDS IN PREVALENCE OF OBESITYOur findings show that the prevalence of over-weight and obesity (defined as BMI >25 kg/M2)and obesity (BMI >30 kg/M2) increased consis-tently in all age and socioeconomic groups ofSwedish men during the 1980s. During a similarperiod (1980-87) in the upper midwestern regionof the USA, the prevalence of obesity, defined asBMI >30 16 kg/M2 (85th centile at year 1980),increased by 0 6%/year in men aged 25-74

Table VII Effect of timle period on the prevalenice ofoverweight and obesity (body nmass index (BMI) >25kglnz2) anid of obesity (BMI >30 kgnm2) in different agegroups after adjustnment for the effect of education,socioeconomic group, region, and nationality (odds ratios(OR) with 95% confidence intervals (CI)).

Age group (y)

16-2425-3435-4445- 5455-6465-7475--84

Total 16-84

BMI >25 kg/nI2OR 95% CI

1-13 0-85, 1 491 36 1 12, 1 65119 099, 1431-16 0 96, 1 41118 096, 145106 086, 1-311-11 0-85, 1-451-20 1 11, 130

BMI >30 kg/ni2OR 95.CI0 81 0 35, 1 881-04 062, 1 751-47 0-99, 2-18119 080, 1761-22 0-84, 1-770-96 064, 1421 35 0 81, 2 261 17 099, 139

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Table VIII Effect of the time period on the prevalence of overweight and obesity, (body,mass index (BMI) >25 kglm2) and of obesity (BMI 30kg/nm2) in different socioeconomiicgroups after adjustnment for the effect of age, education, regiotl and nationality (oddsratios (OR) with 95% confidence intervals (CI)).

BMI >25 kg/rn12 BMI >30 kg,m2Socioeco?nom;zic grolups OR 95 % CI OR 95% CI

Manual workers 1 15 1 02, 1 29 1 23 0 97, 1-57Junior salaried employees 1 08 0-82, 1-43 0-93 0-54, 1 61Intermediate salaried employees 1 21 0 97, 1-51 1-08 0-63, 1-85Senior salaried employees and self employed

professionals 1-41 1 10, 1-80 1-16 0-65, 2 09Farmers 1 16 0-88, 1-53 1 20 0-74, 1-95Entrepreneurs 1.24 0-80, 1-93 1 29 0 54, 3 05Students 1-26 0-76, 2-10 0-42 0-08, 2-24All socioeconomic groups 1-18 1 09, 1-28 1-16 0 97, 1-38

years.'0 A similar absolute increase (about 4%over seven years) in the prevalence of obesity,defined as BMI=27-30 kg/m2,'1 was observed inThe Netherlands in 1976-80 among men 37-43years of age. In Finland, between 1972 and 1982,an increase in the prevalences of BMI >25 kg/M2and BMI >30 kg/M2 in men were particularlypronounced in the 40-59 years aged group but notin the 30-39 year age group.12 In Denmark, theprevalence of obesity (BMI >30 kg/M2) showed a

steep increase in the birth cohorts, beginning inthe early 1940s and levelling off thereafter.13 14

The most dramatic increase in the prevalence ofobesity among men was reported from Czecho-slavakia between 1985 and 1988. The proportionof obese men in the 25-64 year age group rosefrom 18-5% to 23-9%, p<0 001.16These data indicate that the mean BMI and the

prevalence of obesity generally increased in adultmen in both Europe and the United States, withsome exceptions. It should be pointed out that inmost of the studies information about the BMIwas available for only two or three points in time.Moreover, in not all studies were the mean BMIand prevalence of obesity adjusted for differencesin age and in the distribution of other socio-

demographic parameters in successive surveys.An advantage of the present study was the avail-

ability of sociodemographic characteristics whichmade it possible to adjust for potential effects of

confounding variables.

SOCIODEMOGRAPHIC TRENDS

Our study includes a broader range of age,education, socioeconomic status, geographicalregion, and ethnic origin than do more limitedsamples, which tend to be more homogeneous andvery often limited to one region only. The resultsconcerning adult Swedish men in nationallyrepresentive samples confirm that there is a strongpositive association between BMI and the preva-lence of obesity in relation to age. This associationvaries, however, among socioeconomic groups: itis strongest among farmers and very weak amongsenior salaried employees and self employed pro-fessionals. The significant inverse relationbetween education and socioeconomic group andthe BMI in men agrees with a trend amongAmerican men.7 29 35

Native born Swedes living in Stockholm have alower BMI than those who live in other largemunicipalities and geographical regions and whoare not native Swedes. Our results agree withstudies showing differences in the prevalence ofobesity between those living in rural and urbanenvironments26 and among various ethnicgroups. 33

In summary, there are clear sociodemographicpatterns of obesity in various populations. Thesepatterns should be taken into account in planningeffective means of preventing and controllingobesity.

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