Table 4.
Hazard ratios (HR) of incident hypertension with each 1 serving/d per week increasing consumption of dairy and milk products (2340 participants)* (β Coefficients, hazard ratios and 95 % confidence intervals)
| Model 1† | Model 2‡ | Model 3§ | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| β | HR (95 % CI) | P | β | HR (95 % CI) | P | β | HR (95 % CI) | P | ||||
| Total dairy products (serving/d) | −0·084 | 0·92 | 0·86, 0·99 | 0·02 | −0·077 | 0·93 | 0·86, 0·996 | 0·04 | −0·084 | 0·92 | 0·86, 0·99 | 0·02 |
| Total high-fat dairy products (serving/week) | −0·022 | 0·98 | 0·96, 0·996 | 0·02 | −0·030 | 0·97 | 0·95, 0·99 | 0·002 | −0·030 | 0·97 | 0·95, 0·99 | 0·002 |
| Fluid milk (serving/week) | −0·005 | 1·00 | 0·98, 1·01 | 0·39 | −0·004 | 1·00 | 0·98, 1·01 | 0·53 | −0·005 | 1·00 | 0·98, 1·01 | 0·45 |
| Whole milk (serving/week) | −0·012 | 0·99 | 0·96, 1·02 | 0·43 | −0·024 | 0·98 | 0·95, 1·01 | 0·15 | −0·017 | 0·98 | 0·95, 1·02 | 0·30 |
| Cheese (serving/week) | −0·017 | 0·98 | 0·96, 1·01 | 0·20 | −0·020 | 0·98 | 0·95, 1·01 | 0·15 | −0·022 | 0·98 | 0·95, 1·01 | 0·11 |
| Yoghurt (serving/week) | −0·068 | 0·93 | 0·89, 0·98 | 0·002 | −0·058 | 0·94 | 0·90, 0·99 | 0·01 | −0·055 | 0·95 | 0·90, 0·99 | 0·02 |
| Fermented milk products (serving/week) | −0·027 | 0·97 | 0·95, 0·99 | 0·01 | −0·027 | 0·97 | 0·95, 0·995 | 0·01 | −0·028 | 0·97 | 0·95, 0·99 | 0·01 |
| Total low-fat/fat-free dairy products (serving/week)║ | −0·021 | 0·98 | 0·96, 0·999 | 0·04 | −0·020 | 0·98 | 0·96, 1·00 | 0·06 | −0·022 | 0·98 | 0·96, 0·999 | 0·04 |
| Multiplicative term of low-fat/fat-free dairy products and follow-up time | 0·003 | 1·00 | 1·00, 1·01 | 0·07 | 0·003 | 1·00 | 1·00, 1·01 | 0·04 | 0·003 | 1·00 | 1·00, 1·01 | 0·04 |
| Skimmed and low-fat milk (serving/week)║ | −0·025 | 0·98 | 0·95, 0·997 | 0·03 | −0·025 | 0·98 | 0·95, 0·998 | 0·04 | −0·027 | 0·97 | 0·95, 0·997 | 0·02 |
| Multiplicative term of skimmed/low-fat milk and follow-up time | 0·004 | 1·00 | 1·00, 1·01 | 0·02 | 0·004 | 1·00 | 1·00, 1·01 | 0·01 | 0·004 | 1·00 | 1·00, 1·01 | 0·01 |
| Cream and butter (serving/week)║ | −0·025 | 0·98 | 0·96, 0·99 | 0·005 | −0·031 | 0·97 | 0·95, 0·99 | <0·001 | −0·029 | 0·97 | 0·95, 0·99 | 0·002 |
| Multiplicative term of cream/butter and follow-up time | 0·002 | 1·00 | 1·00, 1·01 | 0·03 | 0·002 | 1·00 | 1·00, 1·01 | 0·04 | 0·003 | 1·00 | 1·00, 1·01 | 0·03 |
Dairy/milk products consumption was calculated by using the cumulative average consumption before the onset of incident hypertension or before the end of the study, and entered into models as a continuous, time-varying variable. Total dairy products included skimmed/low-fat milk, whole milk, sherbet/ice milk, ice cream, yoghurt, cottage/ricotta cheese and other cheese (e.g. American, Cheddar, etc.). Low-fat dairy products included skimmed/low-fat milk, sherbet/ice milk and yoghurt. High-fat dairy products included whole milk, ice cream, cottage/ricotta cheese and other cheese (e.g. American, Cheddar, etc.). Fluid milk includes skimmed/low-fat milk and whole milk. According to the definition by the US Department of Agriculture MyPlate Dairy Group( 28 )and the Dietary Guidelines for Americans( 29 ), milk products with little to no Ca (e.g. cream cheese, cream and butter) are not included in the Dairy Group. Therefore, for the present study, we did not include cream, sour cream, cream cheese and butter in any of the dairy groups. However, for the purpose of comparison, we created a separate group ‘Cream and butter’ by summing the intake of these four milk products. In addition, the ‘Fermented milk products’ group includes sour cream, yoghurt, cottage/ricotta cheese, cream cheese and other cheese (e.g. American, Cheddar, etc.). For all dairy/milk products, we used unit ‘servings’ to facilitate the comparisons across different diary/milk products. The conversion algorithm between ‘serving’ and ‘gram’ is 1 serving skimmed/low-fat milk=245 g; 1 serving whole milk=244 g; 1 serving cream=15 g; 1 serving sour cream=12 g; 1 serving sherbet/ice milk=96 g; 1 serving ice cream= 66 g; 1 serving yoghurt=227 g; 1 serving cottage/ricotta cheese=105 g; 1 serving cream cheese=28 g; 1 serving other cheese (e.g. American, Cheddar, etc.)=28 g; 1 serving butter=5 g.
Model 1: adjusted for sex, baseline age; time-varying total energy intake; and the multiplicative term of follow-up time with age.
Model 2: model 1+time-varying smoking status, physical activity, modified Dietary Guidelines Adherence Index (DGAI) score (i.e. DGAI score excluding sub-scores for assessing the consumption amount of milk and milk products and the likelihood of choosing low-fat milk and milk products) and caffeine coffee intake; and the multiplicative terms of follow-up time with physical activity.
Model 3: model 2+BMI at the beginning of each exam interval.
The hazard of incident hypertension are non-proportional by the consumption of total low-fat/fat-free dairy foods, skimmed/low-fat milk or cream/butter (i.e. Cox proportional assumption is violated).