Coffee Consumption and Risk of Myocardial Infarction among Older Swedish Women SA Rosner, A...
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Transcript of Coffee Consumption and Risk of Myocardial Infarction among Older Swedish Women SA Rosner, A...
Coffee Consumption and Risk of Myocardial Infarction among Older Swedish Women
SA Rosner, A Akesson,MJ. Stampfer, A Wolk;
AJE; 2007 165:288-293
Does coffee consumption increase coronary heart disease (CHD) risk?
Case control studies suggested YES Majority of cohort studies suggested NO Most recent cohort studies have shown both
increased risk and decreased risk
Plausibility of decreased risk: Coffee has anti-oxidant properties and
improves insulin sensitivity
Study PopulationSwedish Mammography Cohort established 1987-1990 All women in Uppsala & Vastmanland counties, ages 40-74 were
invited to participate in screening Initial 6-page questionnaire (74% response rate) asking about:
diet parity age a first birth height and weight educational level
follow-up questionnaire (70% response rate) in 1997 diet multi-vitamin/supplement use aspirin use cigarette smoking hormone replacement therapy use history of diabetes, hypertension, and hypercholesterolemia family history of CHD physical activity
Study Population
Considered as baseline 1997! Smoking status not elicited in 1987 questionnaire and
smoking is an important confounder of coffee-CHD association
Of the 38,984 women who responded to the 1997 questionnaire, 6,334 were excluded at baseline due to history of MI, ischemic heart disease, stroke, cancer implausible answer to any of the open-ended diet questions implausible caloric intake missing coffee-consumption data or an outcome event during the first month of follow-up
Diet and CHD assessment
Diet: 96 item, self administered food frequency questionnaire
(‘how often on average do you consume…”) Validation with 4 one week diet records: spearman
correlations for coffee were 0.61 CHD (fatal and non-fatal) assessed by linkage to
Swedish Hospital Discharge Register and Swedish Causes of Death Register
(99% completeness in these registers)Diagnostic Criteria according to Swedish National Board of
health and Welfare Validation of registry revealed high sensitivity (94%) and a
high positive predictive value (86%) for MI compared to other countries
Cohort Analyses
Person time started accruing Sept 15, 1997 until date of diagnosis of MI, stroke, or cancer (=censored
at time of cancer diagnosis) date of death or Dec 31 2002 whichever occurred first
Time scale = calendar time for Cox proportional hazard model
4 indicator variables for coffee consumption (0-4 cups/week=referent) {Note: too few non drinkers to compare ever/never}
Test for trend using ordinal variable
Results
Person time 165,896 years (in 32,650 women with coffee consumption data)
459 cases of MI 391 non-fatal 68 fatal
Heavy coffee consumers: current smokers HRT use Multivitamin use education
Table 1 continued….
Crude RR
1
1.05
0.85
0.82
0.87
Potential Residual Confounding by Smoking? Restrict to Non-Smokers - 320 cases; 133,014 person-years of follow-up;full covariate adjustment
Coffee Consumption RR§ 95% CI§
0-4 / week 1 -
5-7 / week 0.90 0.52, 1.56
2-3 / day 0.62 0.37, 1.03
4-5 / day 0.58 0.34, 1.01
>6 / day 0.80 0.42, 1.52
P for trend=0.10
Cox Model Stratified by Diabetes StatusNon-diabetics, 400 MI cases; 160,472 person-years
Coffee Consumption RR§ 95% CI§
0-4 / week 1 -
5-7 / week 0.71 0.42, 1.20
2-3 / day 0.57 0.35, 0.91
4-5 / day 0.57 0.35, 0.94
>6 / day 0.55 0.31, 0.98
Cox Model Stratified by BMInormal weight BMI=18.5-24-9 kg/m² (225 cases) and BMI >25 kg/m², (210 cases)
Normal weight Overweight/Obese
Coffee Consumpt
ionRR§ 95% CI§ RR§ 95% CI§
0-4 / week 1 - 1 -
5-7 / week 0.88 0.41, 1.89 0.68 0.34, 1.37
2-3 / day 0.77 0.38, 1.56 0.49 0.26, 0.94
4-5 / day 0.79 0.38, 1.63 0.50 0.25, 0.98
>6 / day 0.56 0.24, 1.34 0.64 0.30, 1.37
Hypothetical Model Stratified by BMInormal weight BMI=18.5-24-9 kg/m² (225 cases) and BMI >25 kg/m², (210 cases)
Normal weight Overweight/Obese
Coffee Consumpt
ionRR§ 95% CI§ RR§ 95% CI§
0-4 / week 1 - 1 -
5-7 / week 0.98 0.60, 1.89 0.75 0.45, 1.47
2-3 / day 1.01 0.92, 1.25 0.59 0.26, 0.90
4-5 / day 1.02 0.85, 1.50 0.45 0.25, 0.98
>6 / day 1.10 0.99, 1.34 0.54 0.30, 0.98
Validity of Exposure Measurement
TP=true positive, FP= false positive, FN=false negative, TN=true negative
Sensitivity= prop. of subjects truly exposed (or classified as exposed by gold standard) who are identified by test/record as exposed
Sensitivity = a / (a+c)
Specificity = prop. of subjects truly unexposed (or classified as unexposed by gold standard) who are identified by test/record as unexposed
Specificity = d / (b+d)
Recorded exposure
True exposure (gold standard) Total
+ -
+ a (TP) b (FP) a+b
- c (FN) d (TN) c+d
total a+c b+d a+b+c+d
Validity of Exposure Measurement
Recorded exposure
True exposure (gold standard) Total
+ -
+ a (TP) b (FP) a+b
- c (FN) d (TN) c+d
total a+c b+d a+b+c+d
TP=true positive, FP= false positive, FN=false negative, TN=true negative
Predictive Value pos.= prop. of subjects with test/record positive is truely exposed (or classified as exposed by gold standard)
PV pos = a / (a+b)
Predictive Value neg. = prop. of subjects with test/record negative is truely unexposed (or classified as unexposed by gold standard)
PV neg. = d / (c+d)
Example: caffeine intake
Recorded coffee drinker
True coffee drinker (gold standard= urine metabolite levels)
Total
+ -
+ 62 22 84
- 7 359 366
total 69 (15%) 381
(85%)
450
Sensitivity= 62/69= 90%
Specificity= 359/381= 94%
Pred value pos= 62/84= 74%
Pred value neg= 359/366= 98%
Recorded coffee drinker
True coffee drinker (gold standard= urine metabolite levels)
Total
+ -
+ 21 26 47
- 2 401 403
total 23
(5%)
427
(95%)
450
Sensitivity= 21/23= 91%
Specificity= 401/427= 94%
Pred value pos= 21/47= 45%
Pred value neg= 401/403= 100%
Example: MI incidence
Recorded MI
True MI Total
+ -
+ 360 9 369
- 21 60 81
total 381 (85%) 69
(15%)
450
Sensitivity= 360/381= 94%
Specificity= 60/69= 87%
Pred value pos= 360/369= 98%
Pred value neg= 60/81= 74%
Recorded MI
True MI Total
+ -
+ 401 2 403
- 26 21 47
total 427
(95%)
23
(5%)
450
Sensitivity= 401/427= 94%
Specificity= 21/23= 91%
Pred value pos= 401/403= 100%
Pred value neg= 21/47= 45%
Note: predictive values depend strongly on the prevalence of the exposure/ disease (i.e. the numbers in both columns), while sensitivity and specificity do not