Table 3.
Odds of depressive symptoms* according to caffeine consumption†: men and women (n 537) aged 20–68 years from two workplaces in north-eastern Kyushu, Japan, 2009
| Quartiles of caffeine intake | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ≤100 mg/d (n 128) | 101–165 mg/d (n 148) | 166–291 mg/d (n 133) | >291 mg/d (n 128) | ||||||||||||||||||
| OR | 95 % CI | OR | 95 % CI | OR | 95 % CI | OR | 95 % CI | P value‡ | |||||||||||||
| Depressed subjects | n 46; 35·9 % | n 50; 33·9 % | n 30; 22·6 % | n 31; 24·2 % | |||||||||||||||||
| Model 1§ | 1·00 | – | 0·85 | 0·51, 1·41 | 0·54 | 0·31, 0·93 | 0·51 | 0·29, 0·90 | 0·005 | ||||||||||||
| Model 2∥ | 1·00 | – | 0·90 | 0·53, 1·55 | 0·55 | 0·31, 0·98 | 0·56 | 0·31, 1·04 | 0·02 | ||||||||||||
| Model 3¶ | 1·00 | – | 0·90 | 0·52, 1·54 | 0·54 | 0·30, 0·97 | 0·57 | 0·31, 1·05 | 0·02 | ||||||||||||
| Model 4** | 1·00 | – | 0·92 | 0·53, 1·59 | 0·58 | 0·32, 1·04 | 0·57 | 0·30, 1·05 | 0·02 | ||||||||||||
MET-h, metabolic equivalent hours; CRP, C-reactive protein.
*Defined as a Center for Epidemiologic Studies Depression Scale score of ≥16.
†Estimated from caffeine contents in green tea and coffee (20 mg and 60 mg of caffeine per 100 ml of green tea and coffee, respectively).
‡P for linear trend obtained from multiple logistic regression analysis with ordinal numbers 1–4 assigned to quartiles of caffeine consumption.
§Model 1: Adjusted for age (continuous), sex and workplace (survey in July or in November 2009).
∥Model 2: Adjusted for factors in model 1 and history of cancer, CVD, diabetes mellitus or chronic hepatitis (yes or no), marital status (married or unmarried), living status (alone or not alone), overtime work (none, <10 or ≥10 h/month), job position (low or middle and high), occupational physical activity (active or sedentary), non-occupational physical activity (<5 or ≥5 MET-h/week), current smoking (yes or no), alcohol drinking (yes or no), BMI (kg/m2, continuous), n-3 PUFA intake (% of energy, continuous), log-transformed red meat intake (g/d, continuous) and log-transformed vegetable and fruit consumption (g/d, continuous).
¶Model 3: Adjusted for factors in model 2 and log-transformed serum CRP concentrations (mg/l, continuous).
**Model 4: Adjusted for factors in model 3 and log-transformed serum folate concentration (ng/ml, continuous).