Epidemiology of NCDs

NCDs Overview - The Silent Spread

• Definition: Chronic, non-infectious, long-duration health conditions.
• Major Types:
  • Cardiovascular diseases (CVDs)
  • Cancers
  • Chronic respiratory diseases (e.g., COPD, Asthma)
  • Diabetes
• Global Burden: Account for ~74% of all deaths worldwide.
• Indian Burden: Leading cause of death (>60%); significant premature mortality (deaths between 30-69 years).

⭐ NCDs are the leading cause of mortality and morbidity worldwide.

NCD Risk Factors - Culprits & Causes

• Modifiable Behavioural Risk Factors:
  • Tobacco use (smoke/smokeless)
  • Unhealthy diet (↓fruits/veg, ↑salt/sugar/fats)
  • Physical inactivity
  • Harmful use of alcohol
• Metabolic Risk Factors (Intermediate):
  • ↑ Blood pressure (Hypertension: ≥ 140/90 mmHg)
  • Overweight/Obesity (BMI ≥ 25 kg/m² / ≥ 30 kg/m²)
  • ↑ Blood glucose (Hyperglycemia)
  • ↑ Blood lipids (Hyperlipidemia)
• Non-Modifiable Risk Factors:
  • Age
  • Sex
  • Genetics/Family history

These factors interact in a 'web of causation'.

⭐ The four major NCDs share four common behavioural risk factors: tobacco use, unhealthy diet, physical inactivity, and harmful use of alcohol.

Measuring NCD Burden - Stats & Stories

• Prevalence: Existing cases at a point in time.
• Incidence: New cases over a period.
• Mortality Rates: Crude (overall), Specific (cause/group), Standardized (age-adjusted).
• DALYs: Disability-Adjusted Life Years. $DALY = YLL + YLD$.

  ⭐ DALYs combine years of life lost (YLL) from premature mortality and years lived with disability (YLD).

• QALYs: Quality-Adjusted Life Years; measures life quality & quantity.
• Attributable Risk (AR): Excess risk in exposed. $AR = I_e - I_u$.
• Pop. Attributable Risk (PAR): Proportion of disease in population due to exposure. $PAR = (I_p - I_u) / I_p$.
• Rule of Halves: Hypertension: many unaware/undiagnosed/untreated/uncontrolled.
• Data Sources: NSSO, NFHS, Cancer Registries, GBD study.

NCD Screening & Surveillance - Detect & Defend

• Screening: Early NCD detection in asymptomatic individuals.
• 📌 Wilson & Jungner's Criteria: Important problem; known history; detectable early; suitable test; accepted treatment; facilities; agreed policy; cost-effective; continuous.
• Types:
  • Mass: Entire population.
  • High-risk/Selective: Specific risk groups.
  • Opportunistic: During routine visits.
• Key Biases:
  • Lead time: Earlier diagnosis, not ↑survival.
  • Length time: Detects slow-growing cases.
  • Volunteer: Participants differ.
• NCD Surveillance: Monitors trends, risk factors; guides policy.
• India (NPCDCS): Screens for Diabetes, HTN, Oral, Breast, Cervical cancers.

⭐ Lead time bias can make a screening test appear to prolong survival when it only advances the time of diagnosis.

Population Screening for Hypertension (Simplified)

NCD Prevention & Control - Action Against Ailments

• Levels of Prevention:
  • Primordial: Prevent risk factor development (e.g., healthy public policies).
  • Primary: Modify risk factors (e.g., tobacco cessation, diet for pre-DM).
  • Secondary: Early detection & treatment (e.g., HTN/DM screening, Pap smear).
  • Tertiary: Limit disability, rehabilitation (e.g., post-stroke care, diabetic foot care).
• Strategies:
  • Population-based: Targets whole community (e.g., salt reduction campaigns).
  • High-risk individual: Targets those at increased risk (e.g., statins for high CVD risk).
• NPCDCS Focus: Health promotion, early diagnosis, management, infrastructure.
• WHO 'Best Buys': Cost-effective (e.g., tobacco taxes, salt reduction, physical activity promotion, aspirin for CVD).

⭐ Primordial prevention aims to prevent the development of risk factors in the first place, like promoting healthy lifestyles from childhood.

High‑Yield Points - ⚡ Biggest Takeaways

• NCDs are India's leading cause of death; CVDs are most common.
• Four major NCDs: Cardiovascular diseases, Diabetes, Cancers, Chronic Respiratory Diseases.
• Key modifiable risk factors: tobacco, unhealthy diet, physical inactivity, harmful alcohol use.
• Primordial prevention (preventing risk factor development) is crucial.
• NPCDCS is the main Indian program for NCD prevention and control.
• Rule of Halves indicates significant under-diagnosis and poor control of NCDs.
• Iceberg phenomenon highlights many undiagnosed NCD cases in the community.