## TL;DR
Chronic diseases — cardiovascular disease, diabetes, cancer, respiratory disease — cause 74% of global deaths. The WHO estimates 80% are preventable through modifiable risk factors: diet, physical activity, tobacco, and alcohol.

## Core Explanation
The "big four" risk factors — tobacco use, unhealthy diet, physical inactivity, harmful alcohol use — share common metabolic pathways: inflammation, oxidative stress, insulin resistance. Interventions targeting the root causes (not just symptoms) yield compounding benefits across multiple disease categories.

## Detailed Analysis
Primary prevention (before disease onset) includes population-level policies: tobacco taxation, trans fat bans, sugar-sweetened beverage taxes. Secondary prevention (early detection) uses screening: mammography, colonoscopy, blood pressure checks. The polypill concept — combining aspirin, statin, and antihypertensive in a single pill — shows 30-40% cardiovascular risk reduction.

## Further Reading
- CDC: Chronic Disease Prevention
- WHO NCD Portal
- Lancet Commission on NCDs