CONTRACEPTION
USE OF ORAL CONTRACEPTIVES DIETARY
HABITS AND ALCOHOL
Eiliv Lund MD, PhD
IN RELATION
TO
CONSUMPTION
Bjarne Roster Jacobsen PhD
Institute of Community Medicine University of Tromse, Norway
Abstract The relationship between oral contraceptive (OC) use, dietary habits and alcohol consumption in young women was studied in Tromss, Norway. A total of 5,800 women aged 20-39 years answered a questionnaire in 1986/1987. Women with long-term duration of OC use reported more frequent intake of meat for dinner, preferred low-fat milk and drank less .coffee. For other food items such as intake of fats, fish, fruit and vegetables, no differences were found. Strong associations were found for alcohol consumption, with increasing frequency of use among long-term users of OCs. These results are discussed in relation to the possible association between OC use and breast cancer in young women.
Introduction Dietary habits, especially the amount of fat, are considered to be potential risk factors for breast cancer (1,2). Thus, such habits could be important confounders for the estimates of relative risk in studies of oral contraceptive (OC) use and breast cancer if OC users differ from never users with regard to dietary habits. The effect of OC use on breast cancer risk has become increasingly uncertain (3, 4) after a number of case-control studies showing increased risk among young women (5-10). Some have argued that the positive association may be due to selection or recall bias (ll), and that the negative studies (12-15) are less likely to be biased. On the other hand, the lack of association in some studies could be due to lack of adequate control of confounders (16). All studies of OC use and breast cancer risk
Submitted for publication February 13, 1990 Accepted for publication May 14, 1990
AUGUST 1990 VOL. 42 NO. 2
171
CONTRACEPTION
among young women have given estimates of relative risk adjusted for the well established fertility risk factors and a few also for alcohol consumption (12,13), but none of the studies have shown estimates adjusted for dietary habits. The purpose of this analysis was to study the associations between OC use, dietary habits and alcohol consumption in a population of young women.
Material and Methods Information on oral contraceptive use, parity, dietary habits and alcohol consumption was collected as part of the third Tromsa Study, a general health survey. This survey was to a large extent a replication of the previous Tromse Heart studies in 1974 and 1979-1980 (17, 18). The present analyses were restricted to women aged 20-39 years at time of the survey. During 1986-1987, a total of 6,404 women in this age-group (82 % of all eligible) attended the screening. Attending women were asked about current use of oc. Information on dietary habits and parity was obtained through a questionnaire given all women who attended the screening. Attenders were asked to fill it in at home and return it by mail. A total of 5,836 women aged 20-39 years (91% of those who attended the screening) did so. The questions on dietary habits were all given as food frequency questions of current diet and should be looked upon as indicators of different pattern of diet and give no opportunity for calculations of total fat or energy intake. The reliability has been tested (19). The associations between different pattern of OC use (total duration of use, use before first pregnancy, start of OC use before the age of 20 years) and different dependent variables were analyzed with adjustment for age (S-year age groups) and parity (nulliparous, parous) by analyses of variance, multiple classification analysis (20). In the analyses, only associations with pcO.01 have been regarded as statistically significant because of the large number of comparisons performed. Due to missing values, the number of respondents may differ from one analysis to the other.
Results About 60% of all women reported some experience with use of oral contraceptives (Table I), but the percentage of ever users was higher in the younger women. About one of five were long-term users, i.e. five years or more. No difference was
AUGUST 1990VOL. 42 NO. 2
CONTRACEPTION
Table I. Percentage distribution of OC use among women aged 20-39 years who answered the questionnaire at the third Tromse Study, 1986-1987
Number
20-29 (2588)
of women
Total duration Never < 5 years 5+ years Unknown
Age-groups 30-39 20-39 (3248) (5836)
of OC use 28.4 46.0 25.1 0.5
46.0 34.0 19.2 0.8
38.2 39.4 21.8 0.6
OC use before first pregnancy
23.4
22.0
22.7
Early first use of OCs Before age 20 Aged 20 years or more
48.0 23.7
17.3 36.7
30.9 30.9
Current
31.0
5.7
16.8
OC users
Table II. Percentage distribution of dietary habits in relation to total duration of OC use, adjusted for age and parity, women aged 20-39 years, Tromse 1986-1987 Dietary
habit
Meat for dinner 3+/week Coffee, 5+ cups per day Prefer low-fat milk Bread, 5+ slices/day Use of table fat on bread Lean fish, 2+/week Fruits daily Vegetables at dinner Uses soft margarine or oil for cooking Milk, 3+ glass/day Pat fish, 2+/week Fats added to dinner,l+/week
AUGUST 1990VOL. 42 NO. 2
Total duration of OC use Never < 5 years 5+ years p-value 30 46 76 36 71 37 40 88
33 40 79 36 67 40 40 89
38 38 80 32 69 36 = -I 90
USE OF ORAL CONTRACEPTIVES DIETARY
HABITS AND ALCOHOL
Eiliv Lund MD, PhD
IN RELATION
TO
CONSUMPTION
Bjarne Roster Jacobsen PhD
Institute of Community Medicine University of Tromse, Norway
Abstract The relationship between oral contraceptive (OC) use, dietary habits and alcohol consumption in young women was studied in Tromss, Norway. A total of 5,800 women aged 20-39 years answered a questionnaire in 1986/1987. Women with long-term duration of OC use reported more frequent intake of meat for dinner, preferred low-fat milk and drank less .coffee. For other food items such as intake of fats, fish, fruit and vegetables, no differences were found. Strong associations were found for alcohol consumption, with increasing frequency of use among long-term users of OCs. These results are discussed in relation to the possible association between OC use and breast cancer in young women.
Introduction Dietary habits, especially the amount of fat, are considered to be potential risk factors for breast cancer (1,2). Thus, such habits could be important confounders for the estimates of relative risk in studies of oral contraceptive (OC) use and breast cancer if OC users differ from never users with regard to dietary habits. The effect of OC use on breast cancer risk has become increasingly uncertain (3, 4) after a number of case-control studies showing increased risk among young women (5-10). Some have argued that the positive association may be due to selection or recall bias (ll), and that the negative studies (12-15) are less likely to be biased. On the other hand, the lack of association in some studies could be due to lack of adequate control of confounders (16). All studies of OC use and breast cancer risk
Submitted for publication February 13, 1990 Accepted for publication May 14, 1990
AUGUST 1990 VOL. 42 NO. 2
171
CONTRACEPTION
among young women have given estimates of relative risk adjusted for the well established fertility risk factors and a few also for alcohol consumption (12,13), but none of the studies have shown estimates adjusted for dietary habits. The purpose of this analysis was to study the associations between OC use, dietary habits and alcohol consumption in a population of young women.
Material and Methods Information on oral contraceptive use, parity, dietary habits and alcohol consumption was collected as part of the third Tromsa Study, a general health survey. This survey was to a large extent a replication of the previous Tromse Heart studies in 1974 and 1979-1980 (17, 18). The present analyses were restricted to women aged 20-39 years at time of the survey. During 1986-1987, a total of 6,404 women in this age-group (82 % of all eligible) attended the screening. Attending women were asked about current use of oc. Information on dietary habits and parity was obtained through a questionnaire given all women who attended the screening. Attenders were asked to fill it in at home and return it by mail. A total of 5,836 women aged 20-39 years (91% of those who attended the screening) did so. The questions on dietary habits were all given as food frequency questions of current diet and should be looked upon as indicators of different pattern of diet and give no opportunity for calculations of total fat or energy intake. The reliability has been tested (19). The associations between different pattern of OC use (total duration of use, use before first pregnancy, start of OC use before the age of 20 years) and different dependent variables were analyzed with adjustment for age (S-year age groups) and parity (nulliparous, parous) by analyses of variance, multiple classification analysis (20). In the analyses, only associations with pcO.01 have been regarded as statistically significant because of the large number of comparisons performed. Due to missing values, the number of respondents may differ from one analysis to the other.
Results About 60% of all women reported some experience with use of oral contraceptives (Table I), but the percentage of ever users was higher in the younger women. About one of five were long-term users, i.e. five years or more. No difference was
AUGUST 1990VOL. 42 NO. 2
CONTRACEPTION
Table I. Percentage distribution of OC use among women aged 20-39 years who answered the questionnaire at the third Tromse Study, 1986-1987
Number
20-29 (2588)
of women
Total duration Never < 5 years 5+ years Unknown
Age-groups 30-39 20-39 (3248) (5836)
of OC use 28.4 46.0 25.1 0.5
46.0 34.0 19.2 0.8
38.2 39.4 21.8 0.6
OC use before first pregnancy
23.4
22.0
22.7
Early first use of OCs Before age 20 Aged 20 years or more
48.0 23.7
17.3 36.7
30.9 30.9
Current
31.0
5.7
16.8
OC users
Table II. Percentage distribution of dietary habits in relation to total duration of OC use, adjusted for age and parity, women aged 20-39 years, Tromse 1986-1987 Dietary
habit
Meat for dinner 3+/week Coffee, 5+ cups per day Prefer low-fat milk Bread, 5+ slices/day Use of table fat on bread Lean fish, 2+/week Fruits daily Vegetables at dinner Uses soft margarine or oil for cooking Milk, 3+ glass/day Pat fish, 2+/week Fats added to dinner,l+/week
AUGUST 1990VOL. 42 NO. 2
Total duration of OC use Never < 5 years 5+ years p-value 30 46 76 36 71 37 40 88
33 40 79 36 67 40 40 89
38 38 80 32 69 36 = -I 90
